Wastewater Certification Review Grade 3 & 4 Oregon

Front 1

Most important factor in preventing accidents at a wastewater plant?

Back 1

Attitude of the employees.

Front 2

Plant influent appears black and has a foul odor each morning. The cause is traced to a pump station at a subdivision which is oversized for the current number of homes in the subdivision. What corrective action can you take?

Back 2

Decrease the distance between the on and off probes in the wet well.

Front 3

Which of the following best describes the term "public relations"?

Back 3

All contacts between the staff of the utility and those outside the staff.

Front 4

What is a cross connection?

Back 4

Result of wastewater coming into contact with potable water.

Front 5

Why is it recommended that approved backflow prevention devices be installed above grade level?

Back 5

To prevent the relief port of the device from ever becoming submerged.

Front 6

Your plant's discharge permit requires that effluent suspended solids be tested 3 days per week. You test five samples per week. What should you report?

Back 6

All five results.

Front 7

At a minimum, how often should contact lists on emergency response plans be verified?

Back 7

Quarterly.

Front 8

According to the Code of Federal Regulations the term "Significant Industrial User" includes.

Back 8

A non-domestic discharger that discharges over 25,000 gallons per day of process wastewater or is subject to specific federal pretreatment standards.

Front 9

What document is used to evaluate compliances with personal protective equipment guidelines?

Back 9

Occupational Safety and Health Standards.

Front 10

Which term describes the calculated amount by which the value of a utility's physical property declines annually at a predetermined rate?

Back 10

Depreciation.

Front 11

According to 40 CFR, a discharge to a municipal separate storm sewer system that is composed of storm water mixed with industrial waste is defined by EPA as a(n)?

Back 11

Illicit discharge.

Front 12

The main detrimental effect infiltration/inflow has on plant performance is to.

Back 12

Cut down the hydraulic detention time.

Front 13

Which of the following explains how to handle a chlorine release?

Back 13

Emergency response plan

Front 14

Which of the following is the most significant problem in using the activated sludge process to treat seasonal cannery waste?

Back 14

Nutrient imbalance

Front 15

An auto flow proportional chlorination system is working properly. However in the morning hours when the flow is increasing, the operator is unable to obtain a chlorine residual. What is causing the problem?

Back 15

Nitrites in the effluent.

Front 16

To achieve an overall threat rating for a specific emergency event, a wastewater utility should consider the frequency of past occurrences, the probability of future occurrences, and

Back 16

Magnitude of impact.

Front 17

Uniforms, i.d., and system logos on wastewater system vehicles are critical components of

Back 17

public awareness and security program

Front 18

First step in solving odor problem at plant?

Back 18

Make an onsite inspection.

Front 19

Comprehensive accident report must be posted for review by all employees once per

Back 19

year

Front 20

Delivery of treatment chemicals and materials can pose a security risk. Which of the following is the best way to reduce a treatment plant's vulnerability?

Back 20

Match all delivered goods with manifest and purchase order.

Front 21

The NPDES permit requires an open channel flow measurement system to provide an accuracy of no worse than

Back 21

plus or minus 10%

Front 22

A plant seeks advice to prepare a new ordinance to the use of sewers, which 3 items have the most impact on the operation of the facility?

Back 22

The amount of flow, strength of wastewater, and the toxicity of the wastewater.

Front 23

usual first step in strategic planning for wastewater utilities?

Back 23

Setting goals and objectives.

Front 24

Systematic process for evaluating the susceptibility of critical facilities to potential threats and identifying corrective actions that can reduce or mitigate the risk of serious consequences associated with these threats?

Back 24

Vulnerability assessment.

Front 25

Wastewaters from manufacturing processes should be kept separate from cooling waters in order to reduce.

Back 25

Volume.

Front 26

Wastes from industry can increase the influent temp, what effect can this have on the secondary treatment process?

Back 26

Organism activity will increase.

Front 27

In order to most effectively secure computers used for instrumented process control from cyber-attacks (computer hackers) at wastewater facilities, a utility should

Back 27

Not directly connect a scada system to the internet.

Front 28

A wastewater plant has a chlorine leak that results in a release of chlorine gas above reportable quantities. which regulation requires the operator in charge to file a report?

Back 28

SARA Title III

Front 29

According to OSHA process safety management regulations, what must the plant management do prior to allowing an outside contractor to upgrade a plant's chlorine feed system?

Back 29

Inform the contractor of known hazard potentials in the work area

Front 30

How often should revenue and expense reports be developed for a public wastewater plant

Back 30

Monthly

Front 31

NPDES permits are effective for a fixed term not to exceed how many years?

Back 31

5

Front 32

The superfund amendment and reauthorization act of 1986, referred to as SARA, Title III primarily provides for local community

Back 32

Emergency planning and community right to know

Front 33

Results obtained from pipe roughness coefficient tests can indicate whether or not

Back 33

friction losses in the pipe are increasing

Front 34

a centrifugal pump works on the principle of changing velocity head to

Back 34

pressure head

Front 35

The pump station with variable freq. drives, two complete pumping unites are provided. What flow should each pumping unit be capable of delivering?

Back 35

The max daily design flow of the station.

Front 36

When determining the suction head or lift of a centrifuge pump, measure the distance from the

Back 36

Water surface to the center line of the impeller

Front 37

The head against which a pump must operate

Back 37

is the sum of the static head and the friction head

Front 38

The wet well water level in a lift station controlled by a bubbler system is much lower than normal, the pumps are running constantly, and the level indicator is high. what is most likely the explanation?

Back 38

The bubbler tube is blocked.

Front 39

What may cause a reduction in the pump discharge rate?

Back 39

Suction lift higher than anticipated

Front 40

If other factors remain constant, the capacity of a centrifugal type pump inscreases when the

Back 40

Speed of the pump is increased.

Front 41

Which type of pump works on the principle of a decrease in the overall specific weight of a confined column of a gas-water mixture?

Back 41

Air lift

Front 42

Which valve is most suitable for a throttling application?

Back 42

Butterfly valve

Front 43

The term suction lift refers to the pressure measured from the center line of the pump

Back 43

Down to the hydraulic grade line

Front 44

Two pumps of the same capacity operate together with a single main. In a typical pump station the discharge will be

Back 44

More than one pump, but not twice as much

Front 45

Which gas is most toxic to humans when inhaled?

Back 45

Hydrogen sulfide

Front 46

What is the safety concern with carbon dioxide

Back 46

Carbon dioxide is heavier than air and may cause oxygen-deficient atmospheres

Front 47

During normal operation of a positive pressure, open-circuit self-contained breathing apparatus, the bypass valve should be

Back 47

fully closed

Front 48

alarm set point for oxygen in an atmospheric monitoring device

Back 48

19.5%

Front 49

Osha requires that three types of atmosphere tests be conducted in a confined space. These must be conducted in a specific order, what test should be done first?

Back 49

oxygen content

Front 50

Threshold limit value time weighted average is what?

Back 50

Max. allowable exposure for 8 hours with no harmful effects.

Front 51

What document is used to evaluate compliance with personal protective equipment guidelines?

Back 51

Occupational safety and health standards

Front 52

Electrical pressure available to cause a flow of current when an electrical circuit is closed?

Back 52

Voltage

Front 53

Besides viscosity, what is an important consideration in the selection of a lubricating oil

Back 53

thermal range

Front 54

A belt driven centrifugal pump was out of service for inspection and impeller replacement. When placed back in service, it produced a lower rate of discharge. The first item to check is whether the

Back 54

impeller shaft key was installed.

Front 55

Maintenance required by mag meters includes checking the

Back 55

flow zero

Front 56

maintenance required for capacitance level indicators includes

Back 56

checking and cleaning the connections

Front 57

the scale that forms on the cathode of an electrolytic process reactor can be removed by flushing the system with

Back 57

dilute nitric acid

Front 58

maintenance required by percent open-closed valve controllers includes

Back 58

manually checking the indicator against the valve opening

Front 59

Erratic performance by pneumatic instruments may be caused by

Back 59

water in the air supply

Front 60

A recently rebuilt centrifugal pump has just been returned to service and is now drawing more amps. What is the most likely cause of this problem?

Back 60

packing is too tight

Front 61

When lubricating electric motors, avoid

Back 61

mixing petroleum base grease with silicon base grease

Front 62

If a gas engine knocks, the most likely cause of the problem is

Back 62

Engine is under a heavy load at a low speed

Front 63

What's the easiest way to determine whether the rotor or the stator on progressive cavity pumps are worn?

Back 63

Track the discharge flow rate over time

Front 64

Improper rotation in a centrifugal pump may cause

Back 64

reduced flow or no flow

Front 65

What are the first external signs of mechanical failure in a gear mechanism?

Back 65

excess heat, noise, and vibration

Front 66

Best way to remove calcium deposits from a hypochlorite solution feed pump?

Back 66

use an acid solution to dissolve the calcium deposits

Front 67

Wear rings are installed in a pump to

Back 67

wear instead of the impeller

Front 68

Misalignment of a driver and a driven piece of equipment can cause

Back 68

premature bearing failure

Front 69

A particular electric motor is wound for 3-phase current. If one phase cuts out while it is in operation

Back 69

The motor will heat and will be damaged unless it is stopped by a thermal control device

Front 70

A condition exists where a large volume of flow is pumped against a low head with a centrifugal pump. This results in the motor getting too hot. The operator closes the valve on the discharge side of the pump so that 20% of the original volume of water is being pumped. Under this new condition,

Back 70

The motor temperature would be expected to decrease

Front 71

If a centrifugal pump vibrates and is noisy, what could be a cause?

Back 71

Air is in the pump

Front 72

The shear pin in a bar screen breaks. the operator removes the unit from service and removes a block of wood from the bar screen, what should the operator do next?

Back 72

Replace the shear pin with another of equal strength.

Front 73

Mechanical seals consist of two subassemblies, which are

Back 73

rotating ring assembly and stationary assembly

Front 74

upon inspecting an idle centrifugal effluent pump, you notice that the shaft is spinning backwards. What should be the first thin you would check in this situation?

Back 74

Check valve

Front 75

Two types of planned maintenance are

Back 75

predictive and preventative

Front 76

if equipment fails, but there is no danger to the public the repair is classified as what?

Back 76

Corrective maintenance

Front 77

The type of maintenance used to extend equipment life, reduce maintenance costs, and increase reliability is referred to as

Back 77

preventative

Front 78

establishing a baseline for the performance of equipment over time is a necessary step in __________ maintenance.

Back 78

Predictive

Front 79

Low velocity in a municipal collection system will most likely result in a plant influent which

Back 79

is septic and exerts a high oxygen demand

Front 80

The plant influent has a white opaque appearance and a BOD of 800 mg/L. The most likely cause for this condition is discharge from a

Back 80

milk processing plant

Front 81

A waste with a high BOD and low suspended solids indicates that a major portion of the solids are in

Back 81

solution

Front 82

As wastewater temperature increase, the solubility of oxygen in the wastewater

Back 82

decreases

Front 83

within what wastewater pH range does hydrogen sulfide cause the most serious corrosion problems?

Back 83

less than 5.0

Front 84

In typical fresh domestic wastewater the ratio of BOD5 to chemical oxygen demand is

Back 84

.5 : 1.0

Front 85

Pipe friction loss increases as the

Back 85

velocity increases

Front 86

Which open channel flow measurement device offers the greatest accuracy at low flow rates?

Back 86

V-notch weir

Front 87

The plant influent becomes septic periodically, which of the following could be added to the influent to help control the problem?

Back 87

Potassium permanganate

Front 88

In wastewater plant influent channels, what is the minimum channel velocity needed to prevent solids from settling out?

Back 88

2 ft/sec

Front 89

Typical range for TSS in domestic influent wastewater is

Back 89

100-300 mg/L

Front 90

Wastewater entering a plant is typically

Back 90

somewhat warmer than unheated tap water

Front 91

What's the best flow velocity to settle out grit?

Back 91

.7-1.4 ft/sec

Front 92

Short circuiting of grit through an aerated grit chamber can be minimized or eliminated entirely by

Back 92

installing a submerged transverse baffle along the wall opposite the diffusers

Front 93

If there is a high head loss across a microscreen, the most probable cause could be

Back 93

a plugged screen

Front 94

Which type of pump should be used to transfer a 5% solids primary sludge to a digester?

Back 94

positive-displacement pump

Front 95

Primary clarifiers are typically designed to remove____of the settleable solids and ___of the BOD.

Back 95

95-99% and 20-50%

Front 96

What flow device typically measures flow of primary sludge flow?

Back 96

magnetic flow meter

Front 97

Worn wearing shoes are often found on

Back 97

the flights of a rectangular clarifier

Front 98

The withdrawal of sludge from a clarifier should be slow in order to

Back 98

prevent the pulling of too much water with the sludge

Front 99

What should an operator do to increase MCRT?

Back 99

Decrease the waste rate

Front 100

What effect does pre-aeration have on downstream secondary plant processes

Back 100

it tends to improve the overall efficiency of solids and cbod removal.

Front 101

For a particular plant there is an optimum range in which the mixed liquid solids concentration must be maintained. What could happen if the concentration were allowed to exceed the range

Back 101

A cloudy, turbid effluent would result.

Front 102

The process of nitrification

Back 102

Consumes about 7.1 lbs of alkalinity to oxidize 1 lb. of ammonia to nitrate

Front 103

what type of activated sludge process has a detention time of 3 to 24 hours and a design F/M ratio of .03-.1?

Back 103

Oxidation ditch

Front 104

When is increased wasting of activated sludge and increasing the aeration tank f/m practiced?

Back 104

Denitrication is occurring in the final settling tank causing rising sludge

Front 105

How can an operator decrease the SRT and the MLSS concentration in an activated sludge plant?

Back 105

Decrease RAS rate and increase the waste rate

Front 106

The fecal coliform group is comprised of Escherichia coli and ____________.

A) streptococcus

B) Enterobactor

C) Klebsiella

D) Citrobacter

Back 106

C) Klebsiella

The total coliform group consists of Eschericia coli, Enterobacter, Citrobacter, and Klebsiella. But only E. coli and Klebsiella comprise the fecal coliform group.

Front 107

Coliform bacteria are ____________.

A) pathogens which cause hepatitis

B) more resistant to chlorination than pathogenic bacteria

C) pathogens which cause typhoid

D) less resistant to chlorination than pathogenic bacteria

Back 107

B) More resistance to chlorination....

Front 108

The typical air-to-solids ratio for a dissolved air floatation unit is __________.

a. 0.02 to 0.04 kg/kg (0.02 to 0.04 lb/lb)
b. 10 to 40 kg/kg (10 to 40 lb/lb)
c. 0.2 to 0.4 kg/kg (0.2 to 0.4 lb/lb)
d. 1 to 5 kg/kg (1 to 5 lb/lb)

Back 108

a. 0.02 to 0.04 kg/kg (0.02 to 0.04 lb/lb)

Front 109

ORP stands for __________.

a. Oxygen Recirculation Pump
b. Oxygen Reclamation Process
c. Oxygen Residual Probe
d. Oxidation-Reduction Potential

Back 109

d. Oxidation-Reduction Potential

Front 110

A confined space atmosphere contains a combustible gas. At what percentage of the Lower Explosive Limit (LEL) for that gas is the atmosphere considered "hazardous"?

19.5%
10%
15%
1%

Back 110

10%

The fact that an atmosphere is considered hazardous when the level of a combustible (or flammable) gas reaches 10% of its Lower Explosive Level (LEL) is part of the definition contained in the OSHA Permit-Required Confined Space regulations. It is important to note that the code actually states E0% of the Lower Flammable Level (LFL)E However, most commercially available gas monitors read the LEL. Therefore, the terms LEL and LFL are used interchangeably.

Front 111

When using an evaporator in disinfection, the chlorine-pressure-reducing valve should be located _________________.

next to the evaporator
inside the evaporator
upstream of the evaporator
downstream of the evaporator

Back 111

Downstream of the evaporator

Front 112

The vapor density of a hazardous gas present in a confined space is 1.15. Where is this gas likely to be found?

at this density, the gas will dissipate immediately
near the ceiling
equally distributed throughout the space
near the floor

Back 112

near the floor

Front 113

A pH drop in an aerobic digester can be caused by ______________.

organic underloading
hydraulic overloading
nitrification or CO2 buildup
clogging of diffusers

Back 113

nitrification or CO2 buildup

Front 114

A “dewatering beach is a component of a(n) ________.

anaerobic digester
centrifuge
belt filter press
aeration basin

Back 114

centrifuge

The dewatering beach of a centrifuge is the conical end of a centrifuge bowl where solids are pushed up and out of the liquid by the screw conveyor. While the solids sit on the beach, some excess water will drain out of the solids by gravity.

Front 115

Potassium permanganate is used for _______________.

stabilization
disinfection
coagulation
odor control

Back 115

odor control

Potassium permanganate’s uses include odor control and iron removal.

Front 116

If a good floc forms before contacting a gravity belt thickener but the slurry exiting the belt is very wet, the most likely cause is _________________.

the rollers are not parallel
the belt tension is too tight
all of the above
the belt is dirty and clogged

Back 116

the belt is dirty and clogged

If the belt of a gravity belt thickener is dirty or clogged, its performance will be greatly reduced.

Front 117

Mean cell residence time (MCRT) is mathematically described as the mass of solids (lb or kg) in a process _____________________.

divided by the mass of solids leaving the process (lb/d or kg/d)
multiplied by the amount of solids entering the system (lb/d or kg/d)
divided by the concentration of solids in the system (mg/L)
multiplied by the concentration of solids in the system (mg/L or ppm)

Back 117

divided by the mass of solids leaving the process (lb/d or kg/d)

Front 118

Aerobic digesters not only digest sludge, but can also be used to _________________.

disinfect the sludge
ferment the sludge
thicken the sludge
filter the sludge

Back 118

Thicken the sludge

Front 119

A good way to measure the biological activity and aeration in your biological reactor is to use the ________________ test.

SOUR
SS
TKN
VSS

Back 119

SOUR

The specific oxygen uptake rate (SOUR) test provides a measurement of the biological activity and effectiveness of your aeration by looking the amount of DO used by your mixed liquor over a specific period of time.

Front 120

If adding sodium bicarbonate to an anaerobic digester for pH control, care should be taken not to overdose because ___________________________.

CO2 will be consumed and can result in a vacuum in the tank
sodium toxicity can result
calcium carbonate can precipitate and cause problems
pH may spike above 12.0

Back 120

sodium toxicity can result

Sodium bicarbonate adds alkalinity. When adding to an anaerobic digester, be careful to avoid sodium toxicity from overdosing.

Front 121

The optimum growth of nitrifying bacteria is typically in a pH range of ___________.

6.5 to 7.5
7.5 to 8.5
5.5 to 6.5
8.5 to 9.5

Back 121

7.5 to 8.5

The optimum growth of nitrifying bacteria is typically in a pH range of approximately 7.5 to 8.5. If the pH drops below 7 the process begins to slow down substantially.

Front 122

For an activated sludge nitrification process, how much alkalinity is required to oxidize 0.45 kg (1 lb) of ammonia

6.70 kg (14.77 lb)
4.65 kg (10.25 lb)
7.72 kg (10.01 lb)
3.2 kg (7.14 lb)

Back 122

3.2 kg (7.14 lb)

Theoretically, 3.2 kg (7.14 lb) is required to oxidize 0.45 kg (1lb) of ammonia. If this loss of alkalinity is not compensated for during nitrification, the pH will drop and the process can fail.

Front 123

Bacteria associated with fixed film reactors can thrive in water with a pH as low as ________.

7.0
3.0
8.5
5.5

Back 123

5.5

The bacteria associated with fixed film reactors can thrive in a pH range of 5.5 to 9.0. However, it should be notice that any sudden pH drop, even within the acceptable, would be damaging to your treatment process.

Front 124

Torque overload in a gravity sludge thickener can be caused by ___________________.

sludge removal rate is too low
excessive chlorination of sludge
DO in thickener is too low
sludge feed rate is too low

Back 124

sludge removal rate is too low

If the sludge removal rate of a gravity thickener is too low, sludge will accumulate. The heavy volume of sludge can cause a torque overload on the thickener’s collection arms.

Front 125

If it is determined you need to add chlorine to your RAS to control a filamentous problem, what is typically the maximum safest dosage used for this process?

10 – 15 kg of chlorine for every 1000 kg of MLVSS (10 lb chlorine for every 1000 lb MLVSS)
8 – 10 kg of chlorine for every 1000 kg of MLVSS (4lb chlorine for every 1000 lb MLVSS)
1 – 2 kg of chlorine for every 1000 kg of MLVSS (1lb chlorine for every 1000 lb MLVSS)
3 – 5 kg of chlorine for every 1000 kg of MLVSS (2lb chlorine for every 1000 lb MLVSS)

Back 125

3 – 5 kg of chlorine for every 1000 kg of MLVSS (2lb chlorine for every 1000 lb MLVSS)

For chlorinating the RAS, dosing below 4 kg of Cl2 per 1000 kg of MLSS (4 lb Cl2 per 1000 lb MLSS) per day is safe. However, this dosage may not be high enough to effectively control the filamentous population. The chlorine dosage can be carefully increased by 2 kg of chlorine per 1000 kg of MLVSS (2 lb Cl2 per 1000 lb MLSS) per day until it has an effect.

Front 126

Hydrogen sulfide is _______________.

insoluble in water, corrosive, and toxic
soluble in water, corrosive, and toxic
soluble in water, non-corrosive, and nontoxic
soluble in water, flammable, and nontoxic

Back 126

soluble in water, corrosive, and

toxic

Hydrogen sulfide gas is corrosive, toxic, and soluble in water. In wastewater, it is usually produced from the anaerobic decomposition of organic matter in the collection system.

Front 127

Class “C” extinguishers are used for ___________.

electrical fires
wood fires
metal fires
gas fires

Back 127

Electrical fires

Class C fire extinguishers are used for fires started in electrical wiring, motors, fuse boxes, and other electrical sources.

Front 128

In the wastewater industry, PLC refers to a _______________________.

Pressure Limit Control
Programmable Logic Controller
Plastic-Lined Conduit
Pump Level Circuit

Back 128

Programmable Logic Controller

PLCs (Programmable Logic Controllers) are commonly used in many operational control systems. They allow operators to use control boards and computers to control certain mechanical setpoints and functions in a wastewater plant.

Front 129

Sludge depth should not be greater than ______________ on gravity drying beds.

5 to 10 cm (2 to 4 in)
46 to 51 cm (18 to 20 in)
20 to 30 cm (8 to 12 in)
30 to 38 cm (12 to 15 in)

Back 129

8-12 in.

For gravity drainage drying beds, the sludge depth should only be 20 to 30 cm (8 to 12 in) for optimal performance.

Front 130

When lime is used in stabilizing solids, how long must a pH of 12 be maintained?

1 day
2 hours
12 hours
30 minutes

Back 130

2 hrs.

In the standard lime stabilization process, sufficient lime is added to the sludge in order to raise the pH to a level of 12 or higher for a minimum of 2 hours in order to destroy or severely inhibit the growth of pathogens and microorganisms. The final stabilized product not only has a very low bacterial hazard but it also produces few odors.

Front 131

For efficient removal, phosphorus must be biologically converted to ______________.

orthophosphate
polyphosphorus
metaphosphorus
organic phosphate

Back 131

orthophosphate

For efficient removal, phosphorus must be biologically converted to orthophosphates in under anaerobic conditions. Then, under aerobic conditions, microorganisms use orthophosphates to create polyphosphates which are stored within the cells.

Front 132

For a trickling filter, organic loading is typically expressed as _____________.

kg BOD (lb BOD)
mg BOD/d (oz BOD/d)
kg BOD/100m2×d (lb BOD/1000 ft2/d)
kg BOD/100m3×d (lb BOD/1000 ft3/d)

Back 132

kg BOD/100m3×d (lb BOD/1000 ft3/d)

Because the wastewater is distributed over the volume of the entire filter, its organic loading is expressed as kg BOD/100m3×d (lb BOD/1000 ft3/d) to help coincide with its operation.

Front 133

Wastewater solids which have been decomposed to relatively inert solids are called ____________.

stable
septic
fresh
organic

Back 133

stable

Stabilization renders solids nonputrescible and inactivates pathogenic organisms.

Front 134

40 CFR Part 503 provides regulations and guidelines for managing _______________.

industrial discharges
laboratory testing
wastewater residuals (biosolids)
toxic pollutant discharge

Back 134

Biosolids

Part 503 is a rule used in the regulation and management of wastewater biosolids. It outlines procedures and guidelines for biosolid application, incineration, or disposal.

Front 135

Sludge cake is moved through a multiple-health furnace by a process called ______________.

rabbling
pushing
dosing
turning

Back 135

rabbling

The furnace consists of a cylindrical steel shell surrounding a number of solid refractory hearths, and a central rotation shaft with rabble arms attached for moving the cake.

Front 136

Thermophilic anaerobic digesters typically operate at a temperature of _____.

80ºC (176ºF)
60ºC (140ºF)
20ºC (68ºF)
40ºC (104ºF)

Back 136

60C

Thermophilic aerobic digesters have insulated reactors and reach a normal operating temperature of 60ºC (140 ºF) through heat generated by the biological degreadation of organic solids.

Front 137

A positive displacement pump should never be started ____________.

with the discharge valve closed
with the discharge valve open
without being primed
before relieving all pressure in the discharge pipe

Back 137

With the discharge valve closed

If the discharge valve of a positive displacement pump is closed when started, pressure will build up inside of the pump and cause severe damage.

Front 138

Most gas piping systems are rated for _____________service.

700 kPa (100 psi)
1050 kPa (150 psi)
1500 kPa (200 psi)
350 kPa (50 psi)

Back 138

150psi

Most gas piping systems are rated for 1050 kPa (150 psi)service. Gas pressure from biological processes can exceed this pressure and cause an explosive rupture. Therefore, when isolating a pump or pipe, be sure to allow for venting as a safety precaution.

Front 139

An aerated grit chamber must maintain a constant velocity of ___________ for proper operation.

1.2 m/s (4 ft/sec)
0.9 m/s (3 ft/sec)
0.3 m/s (1 ft/sec)
0.6 m/s (2 ft/sec)

Back 139

1 ft/sec

An aerated grit chamber must maintain a constant flow velocity of approximately 0.3 m/s (1 ft/sec). The addition of air in conjunction with this velocity keeps necessary organic material in suspension.

Front 140

What type of Chlorine Institute cylinder repair kit would be used for 907 kg (2000 lb) containers of chlorine?

A
B
D
C

Back 140

B

Chlorine Institute cylinder repair kits should be readily available in the event of a cylinder leak. The common types of kits available are A (70 kg/ 150 lb), B (907 kg/2000 lb), and C (tank trucks, tank cars, and barges).

Front 141

If there is a significant rise in the volatile acid to alkalinity ratio in your anaerobic digester, you should NOT _________________.

increase the sludge withdrawal rate
add seed sludge from a secondary digester or other solids process
extend the mixing time
adjust the digester temperature for an extended period of time

Back 141

increase the sludge withdrawal rate

A significant rise in the volatile acid to alkalinity ratio in your anaerobic digester is an indicator of problems such as hydraulic overload or withdrawing too much sludge. Steps to correct this situation are add new seed sludge, decrease the sludge withdrawal rate, extend the mixing time, and check/adjust temperature in the digester as needed.

Front 142

A water-filled mechanical pump seal not only helps to prevent leaks, but also ___________.

keeps the pump primed
cools the material being pumped
acts as a reserve water supply
prevents pump shaft wear

Back 142

prevents pump shaft wear

Traditional mechanical pump seals with packing have begun to be replaced by fluid filled seals. While this not only prevents leaks, this type of seal also minimizes any friction generated by the pump shaft.

Front 143

Which of the following is a virus?

Shigella
Clostridium
Salmonella
Hepatitis

Back 143

Hepatitis A is a common virus found in wastewater. Its normal route of infection is through ingestion.

Front 144

In order to control odor from hydrogen sulfide, wastewater containing sulfides should be maintained at a pH of ____________.

less than 7
about 7
about 9
less than 4

Back 144

about 9

In order to prevent the odors released from hydrogen sulfide in septic influent wastewater, the pH should be maintained at approximately 9. This basic pH helps prevent the release of the acidic hydrogen sulfide.

Front 145

Which of the following tests best simulates the working of a dissolved air flotation unit?

free drainage test
centrifugal test
jar test
rise rate test

Back 145

rise rate test

The rise rate test provides a very good indication of how well a particular DAF unit is operating. The timed test uses a graduated cylinder and recycle water that has been pressurized in the DAF system.

Front 146

A trickling filter loaded at a rate of 64 kg BOD5/100 m3×d (40 lbs. BOD5/ 1000 ft3/day) would be considered a______________.

intermediate rate filter
roughing filters
low rate filter
high rate filter

Back 146

intermediate rate filter

Intermediate rate filters may be loaded up to 64 kg BOD5/100 m3×d (40 lbs. BOD5/ 1,000 ft3/day). Recirculation of trickling filter effluent is commonly practiced to ensure good distribution and blending of filter and secondary effluents.

Front 147

Jar tests indicate that the best liquid polymer dose for waste stream is 12 mg/L. The flow to be treated is 2.5 mil. gal/day. Determine the gpd setting for the liquid polymer chemical feeder if the liquid polymer is a 60% solution (assume the polymer solution weights 8.34 lb/gal). 1% equals 10,000 mg/L.

100 gpd
50 gpd
25 gpd
10 gpd

Back 147

50 GPD

Front 148

The primary indicator of an upset in your anaerobic digester is _________________.

excess gas production
volatile acids increases/alkalinity decreases
pH increase
carbon dioxide levels drop

Back 148

volatile acids increases/alkalinity decreases

The primary measurable warning sign for anaerobic digestion failure is an increase in volatile acid production as bicarbonate alkalinity decreases. You will also see a fall in pH, decrease in gas production, and excess carbon dioxide in the off-gas.

Front 149

If solids in water have a specific gravity of 1.30, then they are _______________.

30 % heavier than water
3 % lighter than water
13 % heavier than water
30 % lighter than water

Back 149

30% heavier than water

The specific density of a particle is the ratio of its mass to that of an equal volume of water at the same temperature. Water’s specific density is 1.0. Therefore, the particle is 1.3 times heavier than the water it is in or : (1.3 x 100%) E00% = 30% heavier than water.

Front 150

A pH drop in an aerobic digester can be caused by ______________.

clogging of diffusers
nitrification or CO2 buildup
hydraulic overloading
organic underloading

Back 150

nitrification or CO2 buildup

In an aerobic digester, the oxidation of ammonia to nitrate (nitrification) or the dissolution of carbon dioxide into the digester contents in a covered tank can lower pH. Both reactions produce acidic compounds that consume alkalinity and lower pH.

Front 151

Blowers can produce discharge temperatures in excess of ____________.

93°C (200°F)
75°C (167°F)
58°C (136°F)
45°C (113°F)

Back 151

200F

Air piping is often insulated in order to protect operators from burns. Blowers typically have discharge temperatures in excess of 93°C (200°F). This temperature is close to the boiling temperature for water.

Front 152

Heat exchangers are typically used in a wastewater treatment plant for _______________.

warming cold influent
dissolving powder polymer into solution
warming the contents of small clarifiers in cold weather
heating sludge for anaerobic digestion

Back 152

heating sludge for anaerobic digestion

Heat exchangers are commonly used to keep the contents of anaerobic digesters at an optimum temperature. This allows methane-forming bacteria to thrive and function properly.

Front 153

After a settleometer test you have a thin layer of clear supernatant over a poorly settling sludge and your SVI is greater than 150 mL/g. This condition is referred to as ________________.

septic sludge
ashing
sludge bulking
pin floc

Back 153

sludge bulking

Typically poorly settling sludge with a thin layer of supernatant and excessively high SVI are symptoms of sludge bulking problems.

Front 154

What factor is a main contributor to the growth of Nocardia?

low F:M
lower temperatures
the startup of an activated sludge process
shorter MCRT (Mean Cell Residence Time)

Back 154

low F:M

Nocardia foam is usually a problem in activated sludge systems that have very long SRTs. This filamentous microorganism is a slow-grower but can become a nuisance quickly because it floats and can become trapped in tanks where the effluent leaves via a submerged opening. Nitrifying systems, which require a long SRT in order to allow for a sufficient population of nitrifiers to develop, are often plagued with Nocardia problems.

Front 155

Which of the following forms of plant life is necessary for the proper functioning of an aerobic/facultative stabilization or oxidation pond?

algae
water lilies
weeds
cattails

Back 155

Algae

Aerobic and facultative lagoons rely on algal photosynthesis to help provide DO to the system.

Front 156

A dirty filtrate coming from your pressure filter dewatering system indicates either too high a feed pressure or ___________.

the feed sludge solids concentration is too low
lime scales on the edges of your pressure plates
torn/punctured filter media
too little sludge being fed to the system

Back 156

torn/punctured filter media

A dirty filtrate is typically an indicator of too a high a feed pressure forcing some solids through the filter into the filtrate or a ripped/punctured filter media allowing solids to escape. If your pressure system filtrate is high in solids, first try reducing the feed pressure before checking the filter media.

Front 157

You have decided to use chlorine to help control a Nocardia foaming problem. A typical benchmark is to initially apply __________ for every 1000 kg (1000 lb) of mixed liquor volatile solids (MLVSS).

120 kg (120 kg)
80 kg (80 lb)
4 kg (4 lb)
20 kg (20 lb)

Back 157

4 lb

Care must be taken when using chlorine to control filamentous organisms. Too much chlorine can completely destroy the floc structure and create a very turbid effluent. A good benchmark is to initially apply 4 kg (4lb) for every 1000 kg (1000 lb) of mixed liquor volatile solids (MLVSS).

Front 158

The best method for protecting a steel tank from rust is _____________.

maintaining interior humidity
painting
regular washing
adding a protective coating

Back 158

adding a protective coating

Adding special protective coatings (some are available in certain paints) is the best method for rust prevention.

Front 159

A total chlorine dosage of 6.9 mg/L is required for disinfection. If the effluent flow is 3.1 mil.gal/day and the hypochlorite used has 65% available chlorine, how many pounds /day of hypochlorite will be required?

158 lbs/day
512 lbs/day
274 lbs/day
395 lbs/day

Back 159

274 lbs/day

Front 160

The maximum weir loadings for secondary clarifiers range from _____________.

50 – 75 m3/m·d (4000 – 6000 gpd/ft)
80 – 120 m3/m·d (6400 – 9600 gpd/ft)
125 – 250 m3/m·d (10 000 – 20 000 gpd/ft)
300 – 500 m3/m·d (24 000 – 40 000 gpd/ft)

Back 160

125 – 250 m3/m·d (10 000 – 20 000 gpd/ft)

For the secondary clarifiers of most facilities, benchmarks of clarifier operation include maximum weir loadings of 125 – 250 m3/m·d (10 000 – 20 000 gpd/ft) and overflow rates ranging from 24 – 33 m3/m2·d (600 – 800 gpd/ft2).

Front 161

Dominance of flagellates in your mixed liquor indicate ________ ?

low F:M, high SRT
low F:M, low SRT
high F:M, high SRT
high F:M, low SRT

Back 161

high F:M, low SRT

The dominance of flagellates in your mixed liquor indicates a high F:M ratio and a low SRT. The other organisms typically present during these conditions are amoeboids and free-swimming ciliates.

Front 162

Which type of incinerator uses graded silica?

induced draft
double stack
multiple-hearth
fluidized bed

Back 162

fluidized bed

Fluidized bed incinerators use graded silica. The bed is put into a boiling motion by the combustion of the air allowing the combustion air optimum contact with incoming sludge solids.

Front 163

The adverse effect a substance has on a living entity defines that substance’s _________________.

acidity
toxicity
alkalinity
demand

Back 163

Toxicity

Toxicity is the adverse effect a substance has on a living entity. It is the primary function of any sort of wastewater treatment to reduce or eliminate a waste stream’s toxicity.

Front 164

A viscous, jelly-like slime covering a trickling filter or RBC is known as a(n) _____________.

anaerobic film
population
biological growth
filter fouling

Back 164

Biological growth

A biological growth or fixed film is a viscous, jelly-like substance comprised of a large and diverse population of microorganisms to be used for treatment.

Front 165

A ____________ controller receives sensor output from the process variable and compares it to the setpoint or desired result then adjusts the system accordingly.

manual
feedforward
compound
feedback

Back 165

feedback

A feedback controller receives sensor output from the process variable, compares it to the setpoint, and then adjusts the system accordingly. A feedforward controller uses information about the inputs to a process to prevent process errors.

Front 166

Auxiliary fuel requirements in a multiple hearth incinerator are lower for sludges with a high percentage of volatiles. The volatile content of a sludge may be maximized by:

All of the above
Removing sludge inorganics such as grit
Avoiding the use of ferric chloride and lime in the dewatering process
Not digesting the sludge

Back 166

All of the above

Front 167

A vertical column of fluid is also known as _________.

friction factor
viscosity level
head
density height

Back 167

head

The pressure exerted by a height or level of fluid is often referred to as head. If the fluid is not moving, it is often known as static head. Conversely, if the fluid is moving, there is velocity head. Head is typically measured in feet or meters of column height.

Front 168

The detention time of an aerated grit chamber typically ranges from __________ minutes.

20 to 30
3 to 5
1 to 2
10 to 15

Back 168

3 to 5 minutes

The typical detention time of an aerated grit chamber ranges from 3 to 5 minutes (peak). The rotation speed in the chamber should also be maintained to approximately 0.3 m/s (1 ft/sec).

Front 169

The most probable cause of sludge floating to the surface of a secondary clarifier is _________.

a result of ineffective screening
not enough grit in the sludge
settled sludge is not being removed quickly enough
the scraper speed is too high

Back 169

Settled sludge is not being removed quickly enough

Rising sludge in a secondary clarifier is typically caused by sludge being held too long in the tank and going anaerobic. This accumulation can usually be attributed to worn or damaged scraper blades, problems with the sludge removal pumping, low flows through the clarifier, or low-DO mixed liquor entering the clarifiers.

Front 170

A chlorine demand test shows the __________________________.

amount of chlorine needed to kill all coliforms
safe amount of chlorine to add without harming the receiving stream
amount of chlorine needed to remove the chemical oxygen demand
amount of chlorine needed to provide a specific residual after a given time

Back 170

amount of chlorine needed to provide a specific residual after a given time

Chlorine demand is typically determined by subtracting the residual chlorine from the applied dosage. Therefore, a demand test will help determine the dosage needed to supply a desired residual after the appropriate contact time.

Front 171

A flow of 3700 gpd of sludge is pumped to a 37 000 cu ft digester. The solids concentration of the sludge is 6% with a volatile solids concentration of 75%. If the digester reduces volatile solids by 55%, how many lbs/day volatile solids are destroyed per cu ft of digester capacity. Assume the sludge weights 8.34 lbs/gal. Round to the nearest hundreth.

0.06 lbs VS destroyed/cu ft
0.1 lbs VS destroyed/cu ft
0.02 lbs VS destroyed/cu ft
0.04 lbs VS destroyed/cu ft

Back 171

0.02 lbs VS destroyed/cu ft

Front 172

Which type of incinerator uses graded silica?

multiple-hearth
fluidized bed
induced draft
double stack

Back 172

fluidized bed

Fluidized bed incinerators use graded silica. The bed is put into a boiling motion by the combustion of the air allowing the combustion air optimum contact with incoming sludge solids.

Front 173

The discharge pressure for a positive displacement blower in wastewater treatment plant can run as high as _______________.

210 kPa (30 psig)
190 kPa (28 psig)
130 kPa (19 psig)
150 kPa (22 psig)

Back 173

210 kPa (30 psig)

Blower setups must be designed to meet varied airflow requirements. However, there are certain limits to the design criteria for the pumps used in these systems. For a positive displacement blower, the recommended maximum discharge pressure is 210 kPa (30 psig). Often these limits are related to the stresses placed on piping, the equipment, and for safety concerns.

Front 174

The two bacteria primarily associated with nitrification are Nitrosomonas and ________ ?

Nitrofer
Nitrobacter
Nocardia
Nitrothiothrix

Back 174

Nitrobacter

Nitrosomonas and Nitrobacter are aerobic bacteria commonly referred to as "nitrifiers". Because these are the only bacteria involved in nitrification, the process must be carefully maintained.

Front 175

1 cu ft/sec is equal to ________.

30024 gph
500 gpm
0.72 mgd
0.65 mgd

Back 175

.65 mgd

Front 176

Why is the COD test preferred for process control over the BOD test?

much safer to perform than the BOD test
does not take into account chemical content
results are obtained faster
the results give a better view of the biological activity

Back 176

results are obtained faster

Front 177

What type of microorganisms are most prevalent in a young (Low MCRT, High F:M) mixed liquor?

amoebas, flagellates
free swimming ciliates, flagellates
stalked ciliates, rotifers, flagellates
nematodes, rotifers

Back 177

amoebas, flagellates

The dominance of amoebas and flagellates in your mixed liquor indicates a low MCRT and high F:M ratio. The dominance of nematodes and rotifers indicates a high MCRT and low F:M ratio.

Front 178

Which of the following devices is used to measure chlorine flow rates?

rotameter
sonic flow meter
Parshall flume
Venturi meter

Back 178

rotameter

Rotameters are most often used with chlorinators to measure the flow to the disinfection process.

Front 179

The maximum weir loadings for secondary clarifiers range from _____________.

125 – 250 m3/m·d (10 000 – 20 000 gpd/ft)
50 – 75 m3/m·d (4000 – 6000 gpd/ft)
300 – 500 m3/m·d (24 000 – 40 000 gpd/ft)

80 – 120 m3/m·d (6400 – 9600 gpd/ft)

Back 179

125 – 250 m3/m·d (10 000 – 20 000 gpd/ft)

For the secondary clarifiers of most facilities, benchmarks of clarifier operation include maximum weir loadings of 125 – 250 m3/m·d (10 000 – 20 000 gpd/ft) and overflow rates ranging from 24 – 33 m3/m2·d (600 – 800 gpd/ft2).

Front 180

Operators begin to note that the wastewater in the 2 primary sedimentation tanks occasionally looks black and has a strong odor. You look back through the operating logs and note the following: Influent flows through the plant have been fairly constant.

poor quality (high BOD) centrate is being returned to the primary sedimentation tanks
Poor quality (high BOD) digester supernatant is being returned to the primary sedimentation tanks.
wastewater is going septic in the collection system
intermittent industrial discharges such as inks and dyes are causing the sedimentation tank contents to appear black

Back 180

Poor quality (high BOD) digester supernatant is being returned to the primary sedimentation tanks.

Since the problem has not been reported in upstream processes (such as the grit removal system), the problem appears to be developing in the primary sedimentation tanks rather than coming into the plant from the collection system. Since the problem is only noted occasionally, the cause is probably not the centrate which is discharged to the primary sedimentation tanks every day.

Front 181

From a meatpacking plant, food industry, or dairy you would expect to find all of the following pollutants EXCEPT _____________.

fats, oils, and grease
volatile organics
wide variations in pH
high BOD

Back 181

volatile organics

It is expected to have high BOD, FOG, and even variations in pH from a food industry’s effluent. However, it is uncommon to see volatile organics, such as fuels, and organic acids in such an effluent.

Front 182

How many pounds of polymer must be added to 30 gallons of water to make a 0.1% polymer solution?

0.50 lbs
1.50 lbs
0.25 lbs
1.0 lbs

Back 182

.25 lbs

Front 183

Which of the following would be least likely to be a problem in wastewater flows from industries such as commercial laundries and paper manufacturers?

trace metals
BOD
fats, oils, and grease
pH

Back 183

trace metals

Front 184

Which of the following is a sign your trickling filter is organically overloaded and hydraulically underloaded?

bulking
filter flies
snails, moss, and roaches
ponding

Back 184

ponding

Ponding occurs when the spaces of the media become clogged. To help correct this problem, decrease the organic loading and increase the hydraulic loading to promote sloughing.

Front 185

When using a centrifuge, the highest performance and results will be obtained when processing ________________________ sludge.

anaerobically digested primary
anaerobically digested WAS
raw WAS
raw primary

Back 185

anaerobically digested primary

Centrifuges achieve optimal results when processing anaerobically digested primary sludge. When processing this sludge type a cake with 35-40% total solids, 95% solids recovery, can be produced using only 4-6 lbs polymer per dry ton solids.

Front 186

To decrease the heating requirements of an anaerobic digester, _________.

reduce the total solids concentration of the feed sludge
increase the total solids concentration of the feed sludge
reduce the volatile solids content of the feed sludge
increase the feed rate of the sludge

Back 186

increase the total solids concentration of the feed sludge

Sending the highest possible solids concentration to the digester will decrease the volume of sludge to be digested, increase the detention time and therefore reduce the heating requirements.

Front 187

Reasons for flow equalization include all of the following, EXCEPT _________________.

temperature fluctuation control
pH variation damping
flow variation damping
BOD load fluctuation control

Back 187

temperature fluctuation control

Influent flow equalization is used for controlling variations and fluctuations in flow, BOD, solids, and pH as well as dealing with toxic materials or “slugs”.

Front 188

An anaerobic digester is failing when __________.

methane-former numbers decrease
volatile acid concentration increases
alkalinity of the sludge decreases
all of the above

Back 188

all of the above

Instability in digestion occurs when the biological process becomes unbalanced and acid-formers are out-producing methane-formers. Warning signs of this condition are decreased alkalinity and increased volatile acid concentrations.

Front 189

The required polymer dose for your gravity thickener is 8 mg/L. The flow to the thickener is 0.91 mgd. If the polymer solution contains 70% active polymer agent, what should the chemical feeder setting be in mL/min? Remember, 1% = 10 000 mg/L and assume the polymer to weigh 8.34 lb/gal.

42 mL/min
27 mL/min
50 mL/min
35 mL/min

Back 189

27 mL/min

Front 190

The destabilization of sludge particles by decreasing the repulsive forces between particles is called ____________.

equilization
flocculation
coagulation
neutralization

Back 190

coagulation

Coagulation involves the destabilization of sludge particles by decreasing the repulsive forces between the particles. Flocculation is the agglomeration of coagulated particles.

Front 191

If the ammonia concentration in an anaerobic digester exceeds ____________, the environment becomes toxic.

3000 mg/L
1000 mg/L
5000 mg/L
200 mg/L

Back 191

3000 mg/L

An ammonia concentration range of 50 to 200 mg/L is beneficial to anaerobic digestion. Most digesters can handle a concentration up to 1000 mg/L without serious adverse effects. An ammonia level of 3000 mg/L or better is toxic to the digester.

Front 192

Steps used to control filter flies on your trickling filter include increased hydraulic loading, cleaning spray nozzles, occasionally flooding the filter, and __________.

chlorinating the filter
draining the filter for an extended period of time
changing to a new type of media
fumigating the filter and area with pesticides

Back 192

chlorinating the filter

A step that can be used to control filter flies (Psychoda) is to chlorinate the for several hours each week until the situation is controlled. You should maintain a residual in the filter of at least 1 to 2 mg/L to ensure you are destroying the flies and their eggs.

Front 193

The primary method of nitrogen removal in constructed wetland treatment system is ______________________________.

nitrification/dentrification
volatilization
precipitation – adsorption in soils
plant or algal uptake

Back 193

nitrification/dentrification

In a constructed wetland system, microbes transform ammonia to nitrate through nitrification and other microbes convert nitrate to nitrogen gas through denitrification.

Front 194

Typically, foaming problems are found in _______________.

secondary clarifiers
biological reactors
chlorine contact chambers
grit classifiers

Back 194

biological reactors

Even a properly working activated sludge biological reactor will have some foaming (10-25% of the reactor surface). Excess foaming is an indicator to a system upset.

Front 195

Operators that may be required to wear SCBAs cannot ______________.

grow beards
have less than 100% lung capacity
have any facial hair
have recent dental work

Back 195

grow beards

Opertors that may be required to wear SCBA units must have good lung capacity, and must keep cheeks and chin free of facial hair. This means no beards, but properly trimmed mustaches are acceptable.

Front 196

Vane, gear, and lobe all describe what type of pump?

plunger pumps
airlift pumps
positive displacement pumps
centrifugal pumps

Back 196

positive displacement pumps

Gear, vane, and lobe pumps are all types of positive displacement pumps. Positive displacement pumps effectively handle thicker sludges.

Front 197

The desired solids loading rate for a 80-ft diameter clarifier is 40 lbs/day/ sq ft. If the flow to the clarifier is 6.5 MGD, what is the required MLSS concentration?

4615 mg/L
3707 mg/L
3517 mg/L
3920 mg/L

Back 197

3707 mg/L

Front 198

Theoretically, how much influent alkalinity would be required for a nitrification process to have 65 mg/L of alkalinity left in the effluent when the influent ammonia concentration is 17.8 mg/L and the process is achieving 98% conversion of ammonia?

69 mg/L
123 mg/L
189 mg/L
211 mg/L

Back 198

189 mg/L

Front 199

The first step in shutting down a centrifuge is to __________.

turn off the drive unit
turn on the flushing water
turn off the polymer
turn off the feed sludge

Back 199

turn off the feed sludge

The first step is to manually decrease the feed sludge flow to zero. Close the isolation valve to ensure positive shutoff. Then start flushing water and stop polymer feed and polymer dilution water.

Front 200

The typical rotational speed of a RBC is ______________.

20 – 30 rpm
1.0 – 1.6 rpm
10 – 20 rpm
5 – 10 rpm

Back 200

1.0 – 1.6 rpm

For an RBC, a rotational speed of 1.0 to 1.6 rpm allows for adequate contact time with the waste stream.

Front 201

You have just installed a new electrical circuit that uses a 50-ohm resistor and supports 2 amps of current. What is the voltage across this circuit?

25 volts
60 volts
100 volts
40 volts

Back 201

100 volts

Voltage is the electric potential across a circuit and is linearly related to the resistance and amperage of that circuit. Therefore: V = IR Where V is voltage, I is amperage, and R is resistance. Based on this equation: V = (2 A)(50 ohms) = 100 volts

Front 202

Through the biological nitrogen removal process, influent ammonia and TKN are converted into ______________ and released into the atmosphere.

nitrate
nitrogen gas
nitrite
hydrogen gas

Back 202

nitrogen gas

The end result of the biological nitrogen removal process is the disassociation of nitrates into oxygen (used by microorganisms) and nitrogen gas.

Front 203

Muriatic acid is also known as _____________.

ferric chloride
sodium hydroxide
hydrochloric acid
sulfuric acid

Back 203

Muriatic is a common name for hydrochloric acid

Front 204

Upflow fluidized bed reactors are typically used to achieve

filtration of TSS
BOD removal
denitrification
phosphorus removal

Back 204

denitrification

Upflow fluidized bed reactors use an attached-growth process for denitrification. Upflow reactors can achieve biomass concentrations in the range of 25 000 to 30 000 mg/L, which allows much smaller reactor volumes than typical suspended growth processes.

Front 205

Chlorine can be used to control filter flies in trickling filters. The chlorine residual recommended for filter fly control is _______.

0.1 to 0.3 mg/L
1 to 2 mg/L
500 to 600 mg/L
200 to 300 mg/L

Back 205

1 to 2 mg/L

In order to control the proliferation of filter flies on a trickling filter, maintain a chlorine residual of 1 to 2 mg/L to help destroy eggs and possible food sources.

Front 206

Which of the following ions do NOT contribute to alkalinity?

SO4-2
OH-
HCO3-
CO3-2

Back 206

SO4-2

The alkalinity of many surface waters is primarily a function of carbonate, bicarbonate, and hydroxide content. Borates, silicates, and other bases also contribute.

Front 207

Typically the largest source of pollutants for natural bodies of water is _____________.

domestic wastewater
food-processing
hospital waste
nonpoint

Back 207

nonpoint

Nonpoint sources of pollution, such as urban runoff, are typically the primary polluters of natural bodies of water. Other forms of waste are usually collected and treated before release.

Front 208

Treatment processes for wastewater sludges (biosolids) include all of the following EXCEPT __________.

thickening
disinfection
incineration
composting

Back 208

disinfection

Wastewater biosolids can be treated using, thickening, dewatering, stabilization, incineration, composting, and heat drying. Disinfection is a primary concern only for wastewater effluent.

Front 209

A screen system that can be internally or externally fed influent is the ___________.

rotary drum screen
continuous conveyor screen
catenary bar screen
reciprocating rake bar screen

Back 209

rotary drum screen

Rotary drum screens can be internally fed (flow enters the drum from the inside and goes out radially into a channel or tank). Rotary drum screens can also be externally fed (flow enters the drum from a channel or tank and flows into the open drum).

Front 210

A low solids content in the aeration basin is typically indicated by the presence of _________________.

a brown, leathery foam
a black color with a rotten egg odor
floating sludge
a white, fluffy foam

Back 210

a white fluffy foam

A low solids content in the aeration basin leads to a high food-to-microorganism ratio that is indicated by the presence of stiff, fluffy, white foam.

Front 211

When chlorine is introduced to hydrogen sulfide gas, the hydrogen sulfide is ____________.

oxidized and made odorless
not affected
diluted to a weaker concentration
concentrated

Back 211

oxidized and made odorless

Chlorine, ozone, hydrogen peroxide, and other chemicals are used to oxidize hydrogen sulfide and render it odorless.

Front 212

The desired solids loading rate for a 80-ft diameter clarifier is 40 lbs/day/ sq ft. If the flow to the clarifier is 6.5 MGD, what is the required MLSS concentration?

4615 mg/L
3707 mg/L
3517 mg/L
3920 mg/L

Back 212

3707 mg/L

Front 213

Predominance of free-swimming cillates and flagellates in activated sludge indicate?

Low F/M, High SRT
High F/M, Low SRT
High F/M, High SRT
Low F/M, Low SRT

Back 213

High F/M, Low SRT

Studying a sludge sample under a microscope and determining which microorganisms are predominant can tell a lot about an activated sludge system. The presence of mostly free-swimming ciliates and flagellates usually indicates that you are dealing with a young sludge from a recent plant start-up or that the biomass is recovering from a fairly severe upset.

Front 214

Typically denitrified sludge floating on your secondary clarifier indicates ______________.

DO levels are high in your biological reactors
the floc has been sheared
sludge is being held too long in the clarifier blanket
a toxic slug has entered the plant

Back 214

sludge is being held too long in the clarifier blanket

Denitrification may occur in your secondary clarifier if DO levels are too low in your biological reactors or if sludge is being held long enough in the clarifier blanket to allow the DO level to drop to zero.

Front 215

The most common pressurization mode used to operate dissolved air flotation thickeners is __________ pressurization.

recycle
gravity
high
low

Back 215

recycle

DAF units can typically operate in total, partial, and recycle pressurization modes. The most common mode used is recycle.

Front 216

Potassium permanganate is used for _______________.

odor control
stabilization
coagulation
disinfection

Back 216

odor control

Front 217

A control system that uses information about the inputs to a process in order to prevent process errors is known as a ________________ controller.

manual
compound
feed forward
feedback

Back 217

feed forward

Feed forward control use input information, such as plant influent or secondary effluent, to adjust the rate of a chemical feed like chlorine. By using a programmed setpoint for dosage, the feed forward controller will be able to adjust the dosage as conditions change and prevent a process upset.

Front 218

Which of the following chemicals would NOT be used as a coagulant for phosphorus removal?

potassium phosphate
aluminum sulfate
ferric chloride
lime

Back 218

potassium phosphate

Lime, aluminum sulfate, ferric chloride, and organic polymers are all coagulants that can be used in phosphorus removal. Potassium phosphate is not a coagulant.

Front 219

The typical F:M ratio for an extended aeration process ranges from ______________.

0.2 to 0.4
0.4 to 1.5
0.2 to 1.0
0.05 to 0.15

Back 219

0.05 to 0.15

The F:M ratio for an extended aeration process typically ranges from 0.05 to 0.15. An F:M of 0.2 to 0.4 is used for most conventional processes. This low F:M means the extended operation runs using little food for the microorganism population.

Front 220

A secondary clarifier is 75 ft in diameter and receives a combined RAS and primary effluent flow of 4.0 mgd. If the MLSS concentration is 2450 mg/L, what is the solids loading rate on the clarifier?

14 lb/d/ft2
17 lb/d/ft2
12 lb/d/ft2
19 lb/d/ft2

Back 220

19 lb/d/ft2

Front 221

The surface overflow rate for a settling tank is determined from the ___________.

volumetric flow divided by the tank volume
volumetric flow divided by the tank surface area
product of the volumetric flow and tank surface area
sum of the volumetric flow and tank surface area

Back 221

volumetric flow divided by the tank surface area

The surface overflow rate for any settling tank is simply the volumetric flow rate divided by the tank’s surface area. This will give the rate in terms of distance per unit time.

Front 222

The vapor density of a hazardous gas present in a confined space is 1.15. Where is this gas likely to be found?

near the floor
at this density, the gas will dissipate immediately
equally distributed throughout the space
near the ceiling

Back 222

near the floor

The vapor density of air is 1.0. Since the gas has a higher density than air, it is heavier than air. Therefore, it will collect in the lower levels of the confined space.

Front 223

The theoretical dosage of sulfur dioxide when used for dechlorination is ______________.

0.1 mg/L SO2 per 1.0 mg/L chlorine residual
0.5 mg/L SO2 per 1.0 mg/L chlorine residual
5.0 mg/L SO2 per 1.0 mg/L chlorine residual
0.9 mg/L SO2 per 1.0 mg/L chlorine residual

Back 223

0.9 mg/L SO2 per 1.0 mg/L chlorine residual

Front 224

The two chemicals used in an amperometric chlorine analyzer are pH buffer (pH 4) and ____________________.

ammonium hydroxide solution
sodium hydroxide
sodium thiosulfate
potassium iodide reagent

Back 224

potassium iodide reagent

Most online chorine analyzers use amperometric titration. The two solutions used are pH buffer and potassium iodide reagent.

Front 225

Which of the following causes the greatest increase in chlorine demand?

alkalinity increase
phosphate concentration increase
increase in organic matter
pH increase

Back 225

increase in organic matter

While the pH of an effluent can have an impact on the effectiveness of chlorine; the levels of ammonia, organic materials, iron compounds, and sulfur compounds present in the effluent significantly increase chlorine demand.

Front 226

The typical solids loading range for a gravity thickener treating primary sludge is __________.

300 to 350 kg/m2·d (60 to 70 lb/d/sq ft)
100 to 150 kg/m2·d (20 to 30 lb/d/sq ft)
400 to 500 kg/m2·d (80 to 100 lb/d/sq ft)
200 to 300 kg/m2·d (40 to 60 lb/d/sq ft)

Back 226

100 to 150 kg/m2·d (20 to 30 lb/d/sq ft)

To operate a gravity thickener efficiently and ensure optimum performance, an operator must monitor the solids loading and overflow rates and keep them within a prescribed range. When thickening primary sludge, the typical range for solids loading is 100 to 150 kg/m2„ªd (20 to 30 lb/d/sq ft).

Front 227

Which of the following is NOT a type of positive displacement pump?

axial-flow
peristaltic
piston
screw

Back 227

axial

Axial- and radial-flow are types of centrifugal pumps.

Front 228

In order to promote nitrification in an activated sludge process, the ____________ can be lowered.

pH
F:M ratio
wastewater temperature
RAS rate

Back 228

F:M

In order for nitrification to occur, bacteria present need to use ammonia as food. Since carbon is a more desirable food source, reducing the amount of carbon readily available is a good step to take to promote nitrification. Additional steps to take include: Maintain the pH at neutral (or slightly above), the temperature needs to stay up to maintain the respiration rate of the microorganisms and the RAS should be increased.

Front 229

Stuffing boxes are primarily used to keep _____________ out of pump shafts.

oil
electricity
air
horsepower

Back 229

air

Stuffing boxes and packing seals are used primarily to prevent air from entering the pump and to prevent excess leakage at the pump shaft.

Front 230

NPDES permits outline all of the following parameters EXCEPT _________________.

plant safety requirements
monitoring and reporting requirements
discharge location
allowable flows

Back 230

plant safety requirements

NPDES permits outline discharge location, allowable flows, allowable effluent concentrations, monitoring and reporting requirements, and more stringent treatment requirements if necessary. Plant safety is typically outlined by the plant management and OSHA (Occupational Safety and Health Administration).

Front 231

A limiting factor for digester loading is ___________.

hydraulic detention time
pathogen type
pathogen content
sludge color

Back 231

hydraulic detention time

Two criteria may determine a digester’s capacity Ethe hydraulic detention time and the volatile solids loading rate of the incoming sludge. The detention time deals with the flow while the volatile concentration deals with how much treatment time will be required for that particular sludge.

Front 232

Which of the following pH values fall into the range of a well-operated anaerobic digester?

3.2
5.8
8.1
6.9

Back 232

6.9

The typical operating range of an anaerobic digester is 6.8 E7.2. At a pH below 6, the volatile acids become toxic to methane-forming bacteria. At a pH above 8, dissolved ammonia levels will become toxic to the methane-forming bacteria.

Front 233

Which of these industries produces the highest BOD wastewater?

cleaning chemicals manufacturers
metal-finishing plants
dry cleaners
fruit juice processors

Back 233

fruit juice processors

Any industries that discharge large quantities of organic wastes or sugars generate high BOD levels in wastewater.

Front 234

In the contact stabilization process, where is the food absorbed into the process?

clarifier
reaeration reactor
contact reactor
influent

Back 234

contact reactor

The contact stabilization mode requires a short-term contact reactor in which food is adsorbed, a clarifier, and a sludge reaeration reactor with approximately six times the detention time of the contact reactor. In the sludge reaeration reactor, previously adsorbed organics are hydrolyzed and then re-released to the liquid before final stabilization in the contact reactor.

Front 235

Some pressure filter systems for dewatering use a __________ system to help dewater sludges high in oils and grease.

vacuum
heating
precoat
compressed air

Back 235

precoat

Precoat systems may provide performance benefits in systems that have feed sludge that contains high levels of oil and grease or fine materials. To prevent oil, grease, or fines from blinding the filter cloth, a coating of filter aid such as diatomaceous earth is applied to the filter cloth before the injection of the conditioned feed sludge.

Front 236

There are several odor models that can be used to simulate the dispersion of short-term peak concentrations of odors in order to predict when and where odors will be detected around collection system and treatment plant structures. These models include a

fluctuating plume model
odor impact model
modified Lutzack-Ettinger model
Hogstrom model

Back 236

modified Lutzack-Ettinger model

The modified Lutzack-Ettinger process is a variation of the activated sludge process that is able to achieve biological nutrient removal. The Hogstom model, the fluctuating plume model, the TRACE model, the odor impact model and the Illinois Institute of Technology Research Institute model are several odor models that are available in the public domain.

Front 237

In terms of mechanical equipment in a treatment plant, MCC stands for _________.

main circuit conductor
maintenance management center
motor current control
motor control center

Back 237

motor control center

Motor control centers (MCCs) are made up of series of steel cabinets that contain motor starters and breakers for the main electrical service to individual pieces of equipment.

Front 238

The primary limitation of low pressure sprays (fixed nozzles with pressures < or = 103 kPa (15 psi) for overland flow systems is:

high energy costs
less aerosols and wind drift than surface methods
nozzles are subject to plugging
poor distribution of the wastewater

Back 238

nozzles are subject to plugging

The limitations of overland flow systems that use low pressure sprays for wastewater distribution are that the nozzles are subject to clogging and they produce more aerosols than slotted pipes or bubbling orifice distribution methods.

Front 239

Wastewater that contains no measurable DO and nitrate is referred to as __________.

toxic
anaerobic
autotrophic
aerobic

Back 239

anaerobic

Anaerobic wastewater contains no dissolved oxygen as well as no nitrate.

Front 240

The maximum kilowatts drawn over a short period of time (usually 15 minutes) is called the electrical _________.

resistance
demand
power factor
rate

Back 240

demand

The electrical demand is the basis for demand charges which are meant to compensate the electric utility for its investment in additional capacity required to meet theoretical maximum load.

Front 241

Which of the following activated sludge process modes is typically operated with the shortest solids retention time (SRT)?

high-rate aeration
extended aeration
step feed
modified aeration

Back 241

modified aeration

A modified aeration activated sludge process can operate with a MLSS concentration as low as 200 mg/L, an aeration time as low as 1.5 hours and an SRT as low as 0.2 days.

Front 242

The presence of large amounts of filter flies could be caused by any of the following conditions except ____________.

plugged spray orifices or nozzles
excessive hydraulic loading
tall grass and weeds present around the trickling filter
insufficient spray reaching the outside wall of the trickling filter

Back 242

excessive hydraulic loading

Filter flies thrive in environments that get periodic light sprays of wastewater. High hydraulic loading to a trickling filter will keep media continually wet which is not conducive to filter fly breeding. Filter flies can also breed in grass and weeds around a trickling filter that receive occasional sprays of wastewater such as that carried by wind blowing across the trickling filter.

Front 243

The mesophilic temperature range, used in relation to anaerobic digestion, is ____________

10 – 22°C (50 – 72°F)
32 – 38°C (90 – 100°F)
50 – 60°C (122 – 140°F)
45 – 51°C (113 – 124°F)

Back 243

90-100 F

32 – 38°C (90 – 100°F) is the mesophilic temperature range. Most anaerobic digesters are operated in this range.

Front 244

A ____________ controller receives sensor output from the process variable and compares it to the setpoint or desired result then adjusts the system accordingly.

Back 244

feedback

A feedback controller receives sensor output from the process variable, compares it to the setpoint, and then adjusts the system accordingly. A feedforward controller uses information about the inputs to a process to prevent process errors.

Front 245

A visual indicator of a chlorine leak ______________.

can be seen on the leak gauge
can be produced by spraying water on the system
is green or reddish brown deposits on metal
is the presence of white vapors near the floor

Back 245

is green or reddish brown deposits on metal

Chlorine is a very corrosive substance. If there is leak in a chlorine system in the presence of metal, it will corrode that metal and create discolorations of the metal. These discolorations are typically reddish or green in nature. If a visual indicator is present, use an ammonia solution to find the exact location of the leak.

Front 246

Which of the following statements best describes the nitrifying bacteria Nitrosomonas and Nitrobacter?

heterotrophic bacteria that require excessive amounts (more than 4.0 mg/L) of DO to thrive
rapid-growing anaerobic bacteria that require nitrates to live
slow-growing autotrophic bacteria that oxidize inorganic compounds such as ammonia for energy
autotrophic bacteria that can only thrive in water with a pH less then 6.0

Back 246

slow-growing autotrophic bacteria that oxidize inorganic compounds such as ammonia for energy

Nitrifying bacteria are slow-growing autotrophic bacteria that oxidize ammonia nitrogen for energy. It is this slow growth that contributes to an extended mean cell residence time for the nitrification process.

Front 247

What is the proper pH range for maintaining methane-forming bacteria in an anaerobic digester?

4 - 6
6 - 8
2 - 4
8 - 10

Back 247

6-8

In a healthy environment for methane-forming microorganisms, the pH ranges from 6 to 8 with a typical operating range of 6.8 to 7.2.

Front 248

In terms of sludge thickening (primarily gravity thickening), WAS typically can be described as __________.

compacting easily
has a low sludge volume index
settling rapidly
forming a light, fluffy floc that settles poorly

Back 248

forming a light, fluffy floc that settles poorly

WAS is typically more difficult to thicken by gravity than primary sludge. Since WAS has undergone treatment, it tends to form a light, fluffy floc that settles poorly.

Front 249

65 000 gal/day of sludge from a primary clarifier is pumped to a gravity thickener. If the solids content of the sludge is 4% and the surface area of the thickener is 850 sq ft, what is the solids loading rate of the thickener? Assume the weight of the sludge is 8.34 lbs/gal.

12lbs/day/sq ft
26 lbs/day/sq ft
3 lbs/day/sq ft
19 lbs/day/sq ft

Back 249

26 lbs/day/sq ft

Front 250

An ideal carbon to nitrogen ratio for composting sludge is _______________.

500:1
1:500
30:1
1:30

Back 250

30:1

A carbon to nitrogen ratio of approximately 30:1 allows for optimum microbial growth during composting.

Front 251

In the wastewater industry, PLC refers to a _______________________.

Programmable Logic Controller
Pump Level Circuit
Pressure Limit Control
Plastic-Lined Conduit

Back 251

PLC

PLCs (Programmable Logic Controllers) are commonly used in many operational control systems. They allow operators to use control boards and computers to control certain mechanical setpoints and functions in a wastewater plant.

Front 252

For preventive maintenance of a comminutor, how often should the channel be drained and the unit cleaned?

monthly
weekly
annually
daily

Back 252

monthly

For preventive maintenance of a comminutor, the channel should be drained and the unit cleaned on a monthly basis. As always, the maintenance recommendations of the manufacturer of a particular piece of equipment should be carefully followed.

Front 253

To neutralize a sour digester, assume that 1 mg/L of lime need to be added for every mg/L of volatile fatty acids present in the sludge. If the digester contains 242,000 gallons of sludge with a volatile fatty acid concentration of 760 mg/L, how many pounds of lime should be added?

2562 lb
1017 lb
3427 lb
1534 lb

Back 253

1534 lb

Front 254

The recommended oil change frequency for gear reducers operating under favorable conditions and using petroleum-based lubricants is ___________.

1 month or 450 hours of operation, whichever comes first
2 years or 10,000 hours of operation, whichever comes first
6 months or 2500 hours of operation, whichever comes
2 weeks or 200 hours of operation, whichever comes first

Back 254

6 months or 2500 hours of operation, whichever comes

The typical recommended oil change frequency for equipment operating under favorable conditions and using petroleum-based lubricants is 2500 hours or 6 months, whichever comes first. Intervals of 1 to 3 months may be necessary if the unit operates under conditions that tend to deteriorate oil or cause condensation. As always, follow the recommendations of the equipment manufacturer.

Front 255

A properly functioning heated anaerobic digester can have an alkalinity as high as ___________.

1000 mg/L
5000 mg/L
2500 mg/L
500 mg/L

Back 255

5000 mg/L

With the addition of lime to control pH and the production of ammonium bicarbonate during digestion, the alkalinity in a typical heated anaerobic digester can be as high as 5000 mg/L

Front 256

A sludge pump has a bore of 10 in (0.83 ft) and a stroke length of 3 in (0.25 ft). If the pump operates at 32 strokes/minute, how many gpm are pumped? Assume 100% efficiency and volume displacement. Density of the sludge is 7.48 gal/cu ft.

12 gpm
32 gpm
26 gpm
20 gpm

Back 256

32 gpm

Front 257

A centrifugal pump must acheive a flow rate of 550 gpm against a total dynamic head of 75 ft. What would be the water horsepower requirement for this pump, assuming that the liquid to be pumped has a specific gravity of 1.2?

10.8 whp
12.5 whp
15.3 whp
6.4 whp

Back 257

12.5 whp

Front 258

The primary compound formed when chlorine gas is introduced to water is ____________.

sodium chloride
chloroform
bromine chloride
hypochlorous acid

Back 258

hypochlorous acid

Chlorine dissolves quickly into water to form a mixture of hypochlorous and hydrochloric acids.

Front 259

If your RAS rate is too high, what is typically the primary result?

solids will overload the clarifier and wash out
the solids level to the final effluent decreases
aeration in the basin would increase
anaerobic conditions would develop in your secondary clarifier

Back 259

solids will overload the clarifier and wash out

Solids overload occurs when solids enter the clarifier faster than they can be removed. Overload is related to plant flow, RAS flow, and MLSS concentration. Typically, sludge settleometer readings are normal; however, clarifier blankets are high, return rates are high, and effluent solids concentrations are elevated. Adjusting the RAS rate can quickly verify whether solids loading is a problem.

Front 260

As part of the national pretreatment program (40 CFR Part 403), plants with a design flow of more than ____________ must develop an industrial waste pretreatment program.

Back 260

19 000 m3/d (5 mgd)

The General Pretreatment Regulations of Existing and New Sources of Pollution outline the national pretreatment program for the United States. The regulation requires any plant with a design flow over 19 000 m3/d (5 mgd) to develop an industrial waste pretreatment program.

Front 261

Which of the following is NOT a probable cause for excessive sloughing in a rotating biological contactor?

excessive pH changes
high dissolved oxygen levels
excessive changes in flow and/or organic loading
toxic materials in the influent

Back 261

high dissolved oxygen levels

In rotating biological contactors, excessive sloughing is caused by: toxic materials in the influent, excessive pH variations, and drastic changes in flow and loading. These factors cause sloughing because they create conditions that damage the biomass.

Front 262

Wearing rings on a pump are used to _______________.

hold the impeller in place
wear out prior to pump failure
minimize internal leakage
hold the pump shaft in place

Back 262

minimize internal leakage

Wear rings and other forms of packing are used to minimize internal leakage of the fluid being pumped through the stuffing box.

Front 263

Which of the following conditions will lead to the predominance of Thiothrix bacteria in your activated sludge process?

low DO
low F:M
high ph
high sulfide levels

Back 263

high sulfide levels

High sulfide levels, septic wastes, and nutrient deficiencies can all lead to the predominance of Thiothrix bacteria in your activated sludge process.

Front 264

A biotower is an alternative to what wastewater treatment process?

high-purity oxygen tank
activated sludge aeration basin
rotating biological contactor
trickling filter

Back 264

trickling filter

A biotower is a larger form of a trickling filter system. It uses special media to allow high-rate treatment. It is typically used in conjunction with other wastewater processes.

Front 265

Typically the presence of light, stiff, billowy white foam on the surface of an aeration tank is an indicator of ________. Also what action should you take to correct the problem?

low F:M, decrease wasting
high F:M, increase wasting
low F:M, increase wasting
high F:M, decrease wasting

Back 265

high F:M, decrease wasting

Typically the presence of stiff, white foam is an indicator of high F:M, meaning there are not enough microorganisms to consume your pollutants. Therefore, the best solution is to decrease your wasting rate to increase your microorganism population.

Front 266

At temperatures less than _______, the rate of volatile solids reduction drops so low that aerobic digestion processes are rendered ineffective.

20°C (68°F)
10°C (50°F)
40°C (104°F)
30°C (86°F)

Back 266

10°C (50°F)

At process temperatures less than 10„aC (50„aF) aerobic digestion will almost come to a complete stop. This is true of many biological processes.

Front 267

Calcium hypochlorite contains ___________% available chlorine.

85
65
20
40

Back 267

65

Calcium hypochlorite contains 65% available chlorine. Care should be taken when handling calcium hypochlorite to make sure it does not to come into contact with water. This will release hypochlorous and hydrochloric acids which are extremely dangerous.

Front 268

What type of respirator is needed when entering an IDLH (Immediately Dangerous to Life or Health) atmosphere?

supplied air respirator or self-contained breathing apparatus (SCBA)
NIOSH-approved filtering facepiece
full-face cartridge respirator
powered air purifying respirator (PAPR)

Back 268

supplied air respirator or self-contained breathing apparatus (SCBA)

In a IDLH atmosphere, SCBA gear must be worn and properly used to protect workers from injury.

Front 269

The precipitation of magnesium ammonium phosphate throughout an anaerobic digester system is referred to as _______________.

scaling
decaying
crystallization
fouling

Back 269

scaling

The precipitation of magnesium ammonium phosphate or scaling in side the digester system can complicate the process. This scale can hamper pumping and temperature control in the digester.

Front 270

Which of the following is a low-DO filament that is most likely to be found under low F:M conditions?

Nocardia
Sphaerotilus natans
Microthrix parvicella
H. hydrossis

Back 270

Sphaerotilus natans

Sphaerotilus natans is a bacteria that is associated with low DO conditions and an excess of food in the activated sludge process.

Front 271

Which of the following forms of plant life is necessary for the proper functioning of an aerobic/facultative stabilization or oxidation pond?

algae
weeds
water lilies
cattails

Back 271

algae

Aerobic and facultative lagoons rely on algal photosynthesis to help provide DO to the system.

Front 272

The primary use for methanol in wastewater treatment is __________.

as an algicide
for scale prevention
for odor control
as a carbon source to fuel denitrification

Back 272

as a carbon source to fuel denitrification

The primary use of methanol is to provide additional carbon needed to fuel the denitrification process. In a system where all of the organics have been previously removed, the average dosage is 3 mg/L methanol per 1 mg/L NO3- N.

Front 273

The concentration of your polymer is 0.8%. If the feed rate of your polymer is 0.2 L/s (3 gpm), what is the feed rate of the polymer in kg/d (lb/d)?

467 lb/d
386 lb/d
288 lb/d
613 lb/d

Back 273

288 lb/d

Front 274

Which of the following could lead to cavitation in a centrifugal pump?

operation at low flow
the suction lift is lower than the recommended level
head is higher than the head at peak efficiency
pump speed is higher than recommended

Back 274

pump speed is higher than recommended

If the speed of the pump is increased, often so is the velocity of the fluid. This increase in fluid flow can lead to a reduction on fluid pressure and vapor pressure of the liquid. This in turn can lead to cavitation.

Front 275

Gravity thickeners are similar in many ways to a _____________.

biological reactor
clarifier
centrifuge
grit classifier

Back 275

clarifier

Gravity thickeners create calm flow conditions allowing sludge to settle out of the wastewater similar to the way clarifiers remove solids from the waste stream.

Front 276

Hypochlorite (OCl-) and hypochlorous acid (HOCl) constitute _____________.

combined residual chlorine
chlorine demand
total residual chlorine
free residual chlorine

Back 276

free residual chlorine

Chlorine in the form of hypochlorous acid and/or hypochlorite ion is defined as free available or free residual chlorine. Both of these are weak and disassociate easily, therefore their presence indicates an excess or “free” amount of chlorine.

Front 277

Thermophilic anaerobic digesters typically operate at a temperature of _____.

20ºC (68ºF)
80ºC (176ºF)
40ºC (104ºF)
60ºC (140ºF)

Back 277

140 F

Thermophilic aerobic digesters have insulated reactors and reach a normal operating temperature of 60ºC (140 ºF) through heat generated by the biological degreadation of organic solids.

Front 278

The typical depth of a rock media trickling filter is ______________.

1.2 – 3.0 m (4 – 10 ft)
6.0 – 8.0 m (20 – 26 ft)
4.0 – 5.0 m (13 – 16 ft)
0.5 – 1.0 m (2 – 3 ft)

Back 278

1.2 – 3.0 m (4 – 10 ft)

The term trickling filter often applies to shallow rock media filtration systems with a depth of 1.2 E3.0 m (4 E10 ft). Trickling filter systems with greater depths are often referred to as biotowers or biological towers, and the meadia in these systems is usually plastic.

Front 279

Certain soluble organic materials (refractory organics) are resistant to biological breakdown in secondary treatment. The most effective way to remove these organic materials is by using ___________.

reaeration
breakpoint chlorination
lime addition
activated carbon filtration

Back 279

activated carbon filtration

Activated carbon can remove soluble COD and refractory organics by chemical adsorption on its surface as the water is filtered through it.

Front 280

Typically, chlorine is __________________ before entering solution and introduced to the effluent.

mixed
evaporated
ionized
deionized

Back 280

evaporated

Chlorine in large quantities is usually transported in liquid form. Therefore when it is used for disinfection, it is first evaporated and the gas is mixed into a solution before entering the effluent.

Front 281

Motors, couplings, and pumps used for grit removal should be checked ____________ for signs of damage.

monthly
daily
weekly
annually

Back 281

daily

Because of the damaging nature of grit and debris, the sensitive mechanical equipment (motors, couplings, pumps) used to handle these materials should be checked daily for signs of damage.

Front 282

For a confined space entry, all of the following safety equipment is required for each entrant except

portable eye-wash station
an attached retrieval system with adequate attendant support
gas-detection capability
a 5 to 10 minute escape breathing system

Back 282

portable eye-wash station

All of the other requirements listed here Ean attached retrieval system with adequate attendant support, a 5 to 10 minute escape breathing system, and gas detection capability are all required by the OSHA Permit-Required Confined Space regulations for each entrant into the confined space.

Front 283

The pump most commonly used for transferring sludge to a dewatering process is a(n) __________.

air-lift pump
progressing cavity pump
solid-bowl centrifuge
axial–flow centrifugal pump

Back 283

progressing cavity pump

A progressive cavity positive displacement pump is typically used to transfer sludge to a dewatering process

Front 284

Which of the following is a device used for level measurement

Parshall flume
magmeters
Venturi meter
bubbler tube

Back 284

bubbler tube

A bubbler tube system uses a small air supply and the backpressure created by the static head of a tank’s contents to measure the level inside the tank. All other devices listed are typically used for flow measurement.

Front 285

A total of 270 ml/L sludge settled during a 30 min. settleability test. The secondary influent flow is 11 000 m3/d (2.9 mgd). Calculate the RAS flow in m3/d (mgd) as a ratio of the secondary influent flow.

1123 m3/d (0.3 mgd)
2992 m3/d (0.8 mgd)
4069 m3/d (1.1 mgd)
3425 m3/d (0.9 mgd)

Back 285

4069 m3/d (1.1 mgd)

Front 286

What is the best method to prevent short-circuiting in a clarifier?

runner plates on the bottom of the clarifier
increase detention time
use of properly designed baffles on the stilling well and/or around the perimeter of the tank.
temperature control

Back 286

use of properly designed baffles on the stilling well and/or around the perimeter of the tank.

Clarifier influent structures such as baffles help distribute flow evenly throughout the clarifier as well as reduce entrance velocity.

Front 287

Fine bubble diffusers are ________ susceptible to fouling than coarse bubble diffusers.

equally
more
less
never foul

Back 287

more

Fine diffusers are more susceptible to fouling due to their small pore size, making the pores easier to clog.

Front 288

UEL and LEL are terms related to gases and vapors in wastewater treatment. What do these terms typically define?

reactive limits of common gases
the explosive limits of common gases
entropy or dissolution limits of these gases
the exposure limits of common gases

Back 288

the explosive limits of common gases

UEL and LEL stand for the upper and lower explosive limits of a gas or vapor. These are the concentrations at which there is a possibility of explosion from contact with heat or other chemicals.

Front 289

Which of the following disinfection options is typically most effective against viruses?

bromine chloride
UV
ozone
chlorine

Back 289

UV

UV disinfection is proven to be more effective than chlorine and ozone against viruses in certain cases, regardless of the virus involved.

Front 290

Secondary clarifier sludge blankets are typically maintained between __________.

1.2 and 1.5 m (4 and 5 ft)
0.15 and 0.9 m (0.5 and 3 ft)
2.5 and 3.0 m (8 and 10 ft)
1.8 and 2.2 m (6 and 7ft)

Back 290

0.15 and 0.9 m (0.5 and 3 ft)

Typically, clarifiers are operated so that the solids blanket depth is between 0.15 and 0.9 m (0.5 and 3 ft) from the bottom of the clarifier, with an optimal depth typically between 0.3 and 0.6 m (1 and 2 ft).

Front 291

Which of the following chemicals is used to precipitate phosphorus from wastewater

nitrogen oxide
aluminum sulfate
polymer
sulfur dioxide

Back 291

aluminum sulfate

Alum (aluminum sulfate), polyaluminum chloride, and ferric chloride are the chemicals typically used for orthophosphate precipitation.

Front 292

If ozone is used for disinfection, the threshold limit for exposure for operators is ____________ for an eight-hour period.

1.0 mg/m3 (0.5 ppm)
2.0 mg/m3 (1.0 ppm)
0.5 mg/m3 (0.3 ppm)
0.2 mg/m3 (0.1 ppm)

Back 292

0.2 mg/m3 (0.1 ppm)

Prolonged exposure to ozone can lead to potential respiratory problems. The threshold limit for exposure to ozone is 0.2 mg/m3 (0.1 ppm) for an eight-hour workday.

Front 293

An oxidation ditch is most similar to a(n) ______________ process.

plug flow
extended aeration
step-feed
complete-mix

Back 293

extended aeration

The oxidation ditch is a reactor layout that is a variation of the extended aeration process. Typically, wastewater is pumped around a circular or oval pathway by a mechanical aerator or pumping device at one or more points along the flow pathway.

Front 294

All of the following are possible problems that can occur when operating a belt filter press EXCEPT ______________.

low gravity filtrate due to poor conditioning
”blinded” belt
improper air-to-solids ratio
poor belt tracking

Back 294

improper air-to-solids ratio

Typical problems to troubleshoot on a belt filter press include: belt mistracking, plugged (blinded) bet, and low quality filtrate due to poor conditioning.

Front 295

If there is insufficient alkalinity in your wastewater initially, the _____ of an aerobic digester tends to _____ over time

ammonia, increase
temperature, decrease
pH, decrease
alkalinity, increase

Back 295

pH, decrease

During aerobic digestion, alkalinity is often consumed and carbon dioxide is generated during the process. If there is insufficient alkalinity in your wastewater for buffering, these two factors contribute to a decrease in pH for the digester contents.

Front 296

Chemicals such as ammonia and/or trisodium phosphate may at times be added to your wastewater prior to biological treatment in order to ________________.

allow for more DO retention
correct a nutrient imbalance
aid solids settling
condition the RAS

Back 296

correct a nutrient imbalance

Nitrogen and phosphorus are nutrients that are required in significant amounts to support biological processes. In some instances it is necessary to add these nutrients prior to biological treatment.

Front 297

Typically, primary sludges from a clarifier can be thickened to __________.

1.2 to 2% solids
2 to 7% solids
10 to 15% solids
0.3 to 1% solids

Back 297

2 to 7% solids

Primary sludge is typically easier to thicken and dewater than any other sludge produced during treatment. A primary clarifier can be used as a thickening unit by maintaining a sludge blanket and only intermittently removing sludge. The sludge can be thickened to 2 to 7% solids in this manner.

Front 298

At an ammonia (NH3-N) concentration less than _________, the nitrification rate is significantly reduced.

1 mg/L
2 mg/L
5 mg/L
10 mg/L

Back 298

2 mg/L

Ammonia is the food of nitrosomonas. If the ammonia concentration is low, the nitrification rate will slow. Significantly slowing of the nitrification rate is noticeable at ammonia concentrations less than 2 mg/L.

Front 299

Oxidation Reduction Potential (ORP) is most often associated with ___________.

chlorine control
ammonia measurement
influent solids levels
BOD measurement

Back 299

chlorine control

ORP is based on millivolt readings of potential across bipolar electrodes. There is a millivolt change in this potential as chlorine is added to water. These units measure those changes and can provide detailed residual information to be used in control chlorine dosage.

Front 300

A total of 4000 gpd of sludge is pumped to a digester. If the sludge has a 6% total solids content and a volatile solids content of 75%, how many lbs/day volatile solids are pumped to the digester?

990 lb/day
1125 lb/day
1500 ld/day
705 lb/day

Back 300

1500 ld/day

Front 301

If there are not enough filamentous organisms present in your mixed liquor, the sludge floc tends to __________.

form large clumps
dissolve completely
shear into small pieces
settle well

Back 301

shear into small pieces

If there are not enough filamentous microorganisms present in the biomass, the floc structure may be weak, have a tendency to shear into small pieces, and not settle well. However, if the floc contains an overabundance of filamentous microorganisms, the activated sludge will settle very poorly.

Front 302

The most common type of centrifuge used for thickening or dewatering sludge in wastewater treatment is the _________________.

solid bowl centrifuge
disk-nozzle centrifuge
hydrocyclone
basket centrifuge

Back 302

solid bowl centrifuge

The most common type of centrifuge used is the solid bowl centrifuge. In this type of centrifuge, a solid-walled bowl rotates on a horizontal axis

Front 303

Typically UV disinfection dosage is measured during operation by the intensity of the lamps and ____________.

contact time
effluent hardness levels
effluent microorganism levels
effluent solids levels

Back 303

contact time

Although solids, microorganisms, and hardness affect the performance of a UV system, its dosage is measured the intensity of the lamps coupled with the contact time in the effluent channel.

Front 304

You should decrease your wasting rate if __________________________.

sludge begins floating to the surface of the clarifier
billows of white foam appear on the aeration tank surface
the mixed liquor settles too quickly in the clarifier
dark brown scum appears on the aeration tank surface

Back 304

billows of white foam appear on the aeration tank surface

If billows of white foam appear on the aeration tank surface, decrease the WAS rate in order to reduce the F:M ratio. High F:M is a typical cause of stiff, white foam.

Front 305

What is the maximum safe level of ammonia a worker can be exposed to during an 8-hour workday?

50 ppm (mg/L)
1.0 ppm (mg/L)
1000 ppm (mg/L)
0.5 ppm (mg/L)

Back 305

50 ppm (mg/L)

A worker should not be exposed to more than 50 ppm (mg/L) of ammonia during an 8-hour workday.

Front 306

At pH levels below __________, the activated sludge process will completely stop.

8.0
4.0
6.0
2.0

Back 306

2.0

For most activated sludge processes, a range of 6.5 to 8.5 must be maintained. If the process is nitrifying, a more stringent pH range of 7.0 to 8.0 is recommended. At pH levels below 2.0 and above 10.0, the activated sludge process will stop altogether.

Front 307

Which of these pumps uses a flexible membrane between the sludge it is moving and the driving force of the sludge? It uses this membrane along with valves or ball checks to provide the necessary suction and discharge pressures.

progressing cavity
diaphragm
rotary lobe
jet

Back 307

diaphragm

Diaphragm pumps use a flexible membrane between the sludge it is moving and the driving force of the sludge. The membrane and valves or ball checks provide the suction and discharge pressures. The driving force is often provided by a mechanical device or fluid pressure.

Front 308

A useful method of determining a WAS rate is to base it on ___________.

a constant F:M ratio
a target oxygen uptake rate
varying sludge generation
a constant SVI

Back 308

a constant F:M ratio

A useful control method is to waste solids to maintain a constant F:M ratio. By maintaining this F:M, the proper amount of microorganisms are available for the loading conditions.

Front 309

In an aerated grit chamber, diffused air ______________.

starts the decomposition of mciroorganisms
reduces the amount of air needed for activated sludge treatment
allows the heavier grit particles to settle while keeping the lights organic particles in suspension
is used to control odors

Back 309

allows the heavier grit particles to settle while keeping the lights organic particles in suspension

Aerated grit chamber use diffused air to “roll the wastewater and allow the heavier grit particles to settle while keeping organic matter in suspension for use in the remainder of the treatment process.

Front 310

To detect a chlorine leak in a cylinder or valve, what type of chemical or solution should be used?

ammonia
carbon dioxide
hydrogen sulfide
methane

Back 310

ammonia

A spray bottle filled with ammonia can be used to spray down the valves and hosing to check for any chlorine gas leaks. If any chlorine comes into contact with the ammonia, a yellow gas will form giving a visual verification of where the leak is occurring.

Front 311

The final product of denitrification is __________.

carbon
ammonia
nitrogen gas
carbon dioxide

Back 311

nitrogen gas

In denitrification, microorganisms break down nitrates formed during the nitrification process into oxygen and nitrogen gas. After all of the free oxygen is consumed, the microorganisms start to use the nitrate as an alternate oxygen source. The nitrogen gas produced collects into bubbles which rise to the surface and are released to the atmosphere.

Front 312

Sodium bisulfite is used for all of the following functions EXCEPT ____________.

dechlorination
chromium treatment
coagulant
pH control

Back 312

coagulant

Sodium bisulfite is used for dechlorination, pH control, chromium treatment, and as a bactericide.

Front 313

Higher than normal influent grease levels is one of the problems that can lead to __________ in secondary clarifiers.

weir clogging
hydraulic overload
ashing
reduced solids

Back 313

ashing

Excessive grease levels can lead to ashing in the secondary clarifiers. The grease, entrained with floc, will float on the surface of the clarifier and have a slightly white, flaky appearance, similar to ash. Ashing can be caused by other process problems, also.

Front 314

What type of unit removes grit from wastewater?

DAF unit
clarifier
comminutor
vortex separator

Back 314

vortex separator

A vortex grit removal system separates grit from most of the organics and the water in the wastewater. A grit classifier is used for the final washing and dewatering of the grit that has already been removed from the wastewater by the vortex system.

Front 315

RBCs can be designed to be rotated by all of the following EXCEPT:

gear-reduced motors
motor-driven chain and sprockets
diffused air
wastewater flow

Back 315

wastewater flow

Mechanical drives and air can be used to rotate RBCs through the wastewater that is being treated.

Front 316

Lime slakers convert quicklime (CaO) to __________.

calcium hydroxide
calcium hydride
calcium oxide
hydrogen peroxide

Back 316

calcium hydroxide

Lime slakers add water to quicklime (CaO) in order to form hydrated lime, calcium hydroxide – Ca(OH)2. This change in form allows for quicker dissolution in water and better mixing into a wastewater stream.

Front 317

You currently have 10% by volume polymer solution in stock, but you need a 6% solution for your belt press. How much of the 10% solution should be diluted with water to give you 75 L (20 gal) of 6% solution? Assume the specific gravity of both the polymer solution and dilution water are 1.0.

65 L (17 gal)
45 L (12 gal)
97 L (26 gal)
81 L (21 gal)

Back 317

45 L (12 gal)

Front 318

The primary sludge flow to a gravity thickener is 4 L/s (66 gpm). This is blended with a 6 L/s (95 gpm) secondary effluent flow. If the thickener diameter is 8 m (25 ft), what is the hydraulic loading rate in L/s•m2 (gpd/ft2)?

1888 gpd/ft2
1416 gpd/ft2
472 gpd/ft2
944 gpd/ft2

Back 318

472 gpd/ft2

Front 319

Which of the following is NOT one of the main diseases caused by pathogenic organisms found in wastewater?

Cholera
Nocardia
Dysentery
Typhoid

Back 319

Nocardia

Nocardia is not a disease. It is a type of filamentous bacteria which can cause dark brown foam to build-up on the biological reactors.

Front 320

The two design configurations typically available for solid-bowl centrifuges are ___________.

recessed plate and diaphragm
gravity and high-pressure
horizontally and vertically opposed
cocurrent and countercurrent

Back 320

cocurrent and countercurrent

The two design configurations typically available for solid-bowl centrifuges are cocurrent and countercurrent. The major differences in design pertain to the location of the feed ports, the removal of the centrate, and the internal flow patterns of the liquid and solid phases.

Front 321

The actual output of a pumpfs motor is referred to as _______________.

velocity head
water horsepower
wire horsepower
brake horsepower

Back 321

brake horsepower

Brake horsepower is the actual measure of a pump motors output. It determined by taking the rated horsepower of the pump motor and dividing it by the pump efficiency. Brake horsepower is the power applied to the pump shaft.

Front 322

“Classifying” grit refers to __________________.

disposing of grit
washing and dewatering the grit
determining the type of grit present
screening the grit

Back 322

washing and dewatering the grit

Grit classifiers are used for the final washing of organics from grit and dewatering the grit before final disposal. It is important to wash these organics from the removed grit and return the organics to the wastewater treatment process to maintain proper organic levels throughout the treatment process.

Front 323

The valve of a 70 kg (150 lb) chlorine cylinder has a fusible plug in its valve body designed to melt at _______________.

50 to 55 ºC (122 to 131 ºF)
70 to 74 ºC (158 to 165 ºF)
40 to 44 ºC (104 to 111 ºF)
60 to 65 ºC (140 to 149 ºF)

Back 323

70 to 74 ºC (158 to 165 ºF)

The 70 kg (150 lb) chlorine cylinder has a fusible plug in its valve body designed to melt at 70 to 74 ºC (158 to 165 ºF) in order to prevent a hydrostatic rupture of the cylinder.

Front 324

A settling tank’s hydraulic performance depends on surface area, volume, and ___________.

chain and flights
skimmer arms
influent and effluent structures
scum collectors

Back 324

influent and effluent structures

The hydraulic performance of a settling tank depends on its surface area, volume, and the structure for influent and effluent. The influent structures should insure flow is even and calm to promote settling. And the effluent structures should be able to handle flow variations.

Front 325

Psychoda is another name for what trickling filter pest organism?

filter flies
nematodes
fungi
algae

Back 325

filter flies

Psychoda or filter flies usually appear when there is insufficient wetting of the filter media which allows for breeding and egg-laying.

Front 326

One of the most frequent causes of poor activated sludge process performance is ________________.

temperature control
pump types
poor control of solids inventory
improper conditioning chemical dosage

Back 326

poor control of solids inventory

A lack of control over the solids inventory is one of the most frequent causes of poor activated sludge process performance. Dissolved oxygen control is another cause.

Front 327

Proper conditioning chemical dosage is typically determined by _____________.

trial and error
dilution
jar tests
volume ratios

Back 327

jar tests

Conditioning chemical dosage is determined by such tests as jar, filter leaf, buchner funnel, and capillary suction tests.

Front 328

For personal safety, operators need to protect themselves from high ________ levels around blower equipment.

noise
odor
oil and grease
dust

Back 328

noise

Operators should be careful of high noise levels around blower equipment. Noise levels of 85 dbA for a 24-hour or more exposure period require hearing protection.

Front 329

Grit is washed in order to _________.

remove inorganic matter
improve filterability
remove organic matter
enhance settleability

Back 329

remove organic matter

Grit is washed in order to remove organics from the grit. Organic material must be removed before the grit can go to a landfill.

Front 330

How is phosphorus removed from wastewater?

air stripping
chemical addition and sedimentation/filtration
breakpoint chlorination
methanol addition

Back 330

chemical addition and sedimentation/filtration

Phosphorus cannot be converted to a gaseous form and then removed (or vented) from the process like nitrogen. Therefore, phosphorus must be converted to solid form and removed by sedimentation, filtration, or some other solids removal process.

Front 331

Which of the following may be caused by overaeration/mixing in the aeration tank?

denitrification
low F:M
density currents
pin floc

Back 331

pin floc

Overaeration and mixing in a biological reactor can lead to floc shear and the formation of pin floc. Pin floc is often very difficult to clarify without the use of settling aids.

Front 332

If 5 ounces of a dry polymer are added to 15 gallons of water, what is the percent strength of the polymer solution? Remember that there are 16 ounces in a pound.

1%
10 %
0.25 %
0.5%

Back 332

0.25 %

Front 333

Which process removes the most suspended solids from the water in the wastewater treatment process?

preliminary treatment (screening, grit removal)
stabilization
disinfection
primary treatment

Back 333

primary treatment

On average, primary treatment/clarification removes anywhere from 50 to 65% of a wastewaterfs suspended solids.

Front 334

What is the typical cause of ponding on a trickling filter?

excessive biological growth on the media
insufficient filter wetting
insufficient ventilation
foreign material

Back 334

excessive biological growth on the media

Ponding is typically caused by excessive biological growth on the media. A few possible corrective actions are reduction of organic loading; increase in hydraulic loading; and flooding of the filter for 24 hours.

Front 335

Phosphorous is typically removed from wastewater using some or all of the following EXCEPT _____________.

filtration
coagulation/flocculation
sedimentation
comminution

Back 335

comminution

Phosphorus is typically removed using the physical and chemical processes of coagulation/flocculation, sedimentation, and filtration. However at times, either filtration or sedimentation may be excluded from the process.

Front 336

Nitrogen and ___________ are essential nutrients for microbial growth.

phosphorus
chlorine
boron
sulfur

Back 336

phosphorus

Both nitrogen and phosphorus are essential nutrients for microbial growth in biological treatment systems. They can also cause algal blooms and other pollution issues in receiving waters if too much of these substances are released in the plant’s effluent.

Front 337

A trickling filter employed in combination with an additional biological treatment step is called a ___________________.

intermediate rate filter
roughing filter
low rate filter
high rate filter

Back 337

roughing filter

Roughing filters are generally designed to allow a substantial amount of soluble BOD bleed through. An additional treatment process follows the trickling filter in order to complete BOD oxidation.

Front 338

Which of the following methods of wastewater treatment can be best adapted for crop production?

injection
rapid infiltration land treatment
subsurface wastewater infiltration
slow rate land treatment

Back 338

slow rate land treatment

Type 2 slow rate systems, also known as crop irrigation systems, are designed primarily for crop irrigation with wastewater treatment as a secondary objective.

Front 339

Which of the following thickening processes mixes incoming sludge with a pressurized recycle stream as it enters the thickener?

dissolved air flotation thickener
gravity belt thickener
centrifuge
pressure filter

Back 339

dissolved air flotation thickener

Prior to entering a DAF unit, the feed sludge is mixed with a recycle stream that has been pressurized with air. This pressurized stream is used as the air source to float thickened sludge to the top of the unit.

Front 340

Raw domestic wastewater typically contains approximately _______ total phosphorus.

20 – 40 mg/L
1 – 5 mg/L
6 – 20 mg/L
50 – 100 mg/L

Back 340

6 – 20 mg/L

Domestic wastewater typically contains 6 E20 mg/L of total phosphorus. Approximately 5 E10% is removed during primary treatment and 10 E20 % is removed by conventional secondary treatment.

Front 341

For gravity and dissolved air flotation thickeners, the solids loading rate is defined as the weight of solids coming into the thickener divided by the _________________.

diameter of the thickener
circumference of the thickener
volume of the thickener
surface area of the thickener

Back 341

surface area of the thickener

Assuming there is even flow distribution as the sludge comes in, the solids loading rate for these units is the weight of solids coming into the thickener divided by the surface area of the thickener. The correct units to use are mass per area (kg/m2 or lb/ft2)

Front 342

Chemical methods for removing nitrogen involve all of the following EXCEPT ___________.

ammonia stripping
breakpoint chlorination
ion exchange
ferric chloride coagulation

Back 342

ferric chloride coagulation

Coagulation is part of the process used to remove phosphorus from wastewater. Nitrogen removal methods involve physical/biological methods like nitrification and chemical methods such as breakpoint chlorination.

Front 343

PVC stands for ____________.

Polyvinyl Chloride
Pressure Vacuum Container
Polymer Valve Configuration
Pressure Valve Control

Back 343

Polyvinyl Chloride

Front 344

A _________________ consists of a set of windings around a core (coil) and is installed on a line to either step-down or step-up voltage for the electricity traveling through the line.

transformer
limit switch
breaker
motor

Back 344

transformer

A transformer consists of a set of windings around a core (coil) with a primary side that receives power and a secondary side that releases power. Step-down transformers decrease the voltage and step-up transformers increase the voltage.

Front 345

The optimal range for solids loading on a secondary clarifier is __________________.

400 – 500 kg/m2·d (80 – 100 lb/d/sq ft)
100 – 200 kg/m2·d (20 – 40 lb/d/sq ft)
200 – 300 kg/m2·d (40 – 60 lb/d/sq ft)
300 – 400 kg/m2·d (60 – 80 lb/d/sq ft)

Back 345

200 – 300 kg/m2·d (40 – 60 lb/d/sq ft)

If solids loading for a clarifier is the amount of solids distributed over the surface area of a clarifier in a given time. The optimal solids loading for a secondary clarifier is 200 E300 kg/m2·d (40 E60 lb/d/sq ft).

Front 346

A common measure for preventing soil erosion around a lagoon treatment system is through the use of _____________.

trees
plastic sheeting
riprap
steel fencing

Back 346

riprap

Riprap (large stones) are often used with lagoon and wetland systems to minimize soil erosion effects, protect inlet/outlet equipment, control vegetation, and protect bed liners.

Front 347

Which of the following types of diffusers produce large bubbles and turbulent mixing?

membrane diffusers
ceramic porous diffusers
nonporous (fixed orifice) diffusers
tube membrane diffuser

Back 347

nonporous (fixed orifice) diffusers

Fixed-orifice type diffusers usually consist of piping or plating with moderate sized holes drilled into them. Examples of this type are spargers and wide-band non clog units. These diffusers produce large bubbles are used when mixing is more important than oxygen transfer.

Front 348

A common operational problem associated with using lime is the _________ of pumps and feed lines.

clogging
corrosion
overheating
wearing

Back 348

clogging

Quicklime can readily absorb moisture and form semi-solid clumps. Also lime slurries will coat the inside of pipes and pumps and lead to clogging, stoppages and reduced flow. Flushing your lime-pumping system with fresh water on a regular basis may help to alleviate the clogging.

Front 349

Daily consumption of chlorine is typically measured based on ___________.

dosage
ORP
demand
weight of chlorine vessels

Back 349

weight of chlorine vessels

The most accurate method for determining the amount of chlorine used over any period of time is to take readings from the scale on which the containers sit.

Front 350

What type of clarifier uses suction tubes to remove settled sludge?

vortex
RSR (rapid sludge return)
spiral blade
mechanical truss

Back 350

RSR (rapid sludge return)

A RSR clarifier uses siphon tubes or direct pumping to remove solids from the bottom of the clarifier.

Front 351

At a pH above ____, hydrogen sulfide gas will stay in solution.

5
6
8
7

Back 351

8

At a pH of 9.0, 99% of hydrogen sulfide is dissolved in water as the nonodorous hydrosulfide ion. Consequently, at a pH above 8, hydrogen sulfide gas cannot escape from the water it is dissolved in.

Front 352

The pretreatment of wastewater typically takes place ___________________.

before a waste stream enters the collection system
with screens and grit removal
in the collection system
during primary clarification

Back 352

before a waste stream enters the collection system

Pretreatment of wastewater is typically the responsibility of an establishment or industry before their waste enters the collection system. Over the past several years, the regulations for pretreatment have become stringent.

Front 353

What condition/situation might require an operator to chlorinate the RAS?

excessive pathogens in RAS
the presence of excessive filamentous organisms
high SS in effluent
low DO

Back 353

the presence of excessive filamentous organisms

In the event of an overpopulation of filamentous organisms, it may be necessary to chlorinate the RAS in order to control the population. However, care should be taken because the chlorine will also destroy useful organisms as well.

Front 354

Which of the following chemicals is NOT typically used to precipitate phosphorus?

lime
aluminum sulfate
ferrous sulfate
calcium hypochlorite

Back 354

Aluminum sulfate (alum), ferrous sulfate, and lime are the coagulants used to precipitate phosphorus from wastewater.

Front 355

A rotary drum screen is classified as a __________ screen.

coarse
bar
fine
static wedgewire

Back 355

fine

Rotary drum screens are fine screens that are either internally- or externally-fed. Both types of systems use a spray wash system to remove screenings. Externally-fed units also employ the use of a doctor (scraper) blade to help remove screenings.

Front 356

Today, the color of ggroundh wires used in electrical wiring is ___________.

blue
red
green
yellow

Back 356

green

Front 357

What is the average detention time of a primary clarifier?

12-24 hours
4-6 hours
1-2 days
1-2 hours

Back 357

1-2 hours

Primary clarifier detention time is defined as the primary clarifier tank volume divided by the flow through the tank(s). The detention time should be long enough to allow for the removal of nearly all settleable solids. Detention times that are longer than this are unfavorable because the tank contents may become septic which will decrease removal efficiencies.

Front 358

When foam covers the entire surface of a biological reactor, a device known as a __________ can be used to obtain a representative sample of the contents.

chain-and-flight sampler
automatic sampler
surface sampler
bomb sampler

Back 358

bomb sampler

When taking a mixed liquor sample, it is important not to collect foam with the sample because it can taint the results. A bomb sampler can collect a sample once under the surface of the water to avoid collecting foam.

Front 359

One of the most effective chemicals for dechlorination is _______________.

sulfur dioxide
ferric chloride
hydrogen sulfide
sodium hydroxide

Back 359

sulfur dioxide

Sulfur dioxide, hydrogen peroxide, sodium metabisulfite, and sodium bisulfite are chemicals used in dechlorination.

Front 360

In clarifiers, a non-uniform flow condition in which a small percentage of the water travels faster and through a shorter path than the rest of the water in the tank is described as ________ ?

surface loading
short-circuiting
free-flow
sloughing

Back 360

short-circuiting

Front 361

Sludges with longer detention times generally require _________________ polymer for the processes of coagulation and flocculation.

the same amount of
more
less
no

Back 361

more

Sludges like aerobically digested or extended aeration sludges are difficult to dewater. The longer they are kept under aeration the more difficult they are to flocculate. They require more polymer to treat because of this condition.

Front 362

The first indicator of a high organic load coming into a facility is a decrease in ____________.

BOD
scum in the primary clarifier
DO
influent flow

Back 362

DO

Typically the first measurable indicator of a high organic load is a decrease in DO due to the substantial increase in BOD.

Front 363

A rotary spray distribution unit is a component of what treatment process?

trickling filter
aerated grit chamber
secondary clarifier
activated sludge biological reactor

Back 363

trickling filter

A rotary spray distribution unit is one of the primary components of the trickling filter. This unit is designed to evenly distribute primary effluent over the entire surface of the trickling filter.

Front 364

An operator will control the sludge thickness (solids concentration) from a primary clarifier in order to meet the requirements of the _____________.

downstream solids handling units
upstream equalization basin size
downstream disinfection process
upstream grit removal system

Back 364

downstream solids handling units

The necessary thickness of the sludge removed from primary clarifiers is typically depends on the type of downstream solids handling processes downstream. For example if you plan to immediately dewater your primary sludge, if you have primary sludge degritting you will want a very thin sludge (about 0.5% solids)

Front 365

All of the following cations are typically used to precipitate phosphorus from wastewater EXCEPT _______________.

iron
sulfur
aluminum
calcium

Back 365

sulfur

When introduced under the right conditions, aluminum, iron, and calcium will form insoluble precipitates with phosphorus and can then be removed by physical means from the wastewater.

Front 366

In a electrical circuit, a(n) ______________ is used to measure current.

ohmmeter
transformer
ammeter
thermocouple

Back 366

ammeter

An ammeter is used to measure current, while an ohmmeter is used to measure resistance.

Front 367

Venturi tubes, orifice plates, and pitot tubes are all types of ___________ flow meters.

mechanical
differential
magnetic
ultrasonic

Back 367

differential

Venturi tubes, orifice plates, and pitot tubes are types of differential flow meters. Differential head flow meters use an in-pipe constriction that produces a temporary and measurable pressure drop across it.

Front 368

Of the following, which is chlorine MOST LIKELY to be added to?

primary clarifier effluent
WAS
plant influent
secondary clarifier effluent

Back 368

secondary clarifier effluent

Chlorine or other forms of disinfection are always applied to secondary or tertiary treatment effluents.

Front 369

The final product of denitrification is __________.

nitrogen gas
ammonia
carbon
carbon dioxide

Back 369

nitrogen gas

In denitrification, microorganisms break down nitrates formed during the nitrification process into oxygen and nitrogen gas. After all of the free oxygen is consumed, the microorganisms start to use the nitrate as an alternate oxygen source. The nitrogen gas produced collects into bubbles which rise to the surface and are released to the atmosphere.

Front 370

Which of the following air filters will efficiently remove large quantities of dust and larger particles in order to protect blowers?

fluidized-bed liquid filter
viscous impingement
electrostatic precipitators
dry-barrier

Back 370

viscous impingement

Viscous impingement filters trap dust and larger particles on an oil-coated mesh screen. They can handle a large quantity of dust, but often smaller or lighter particles can slip through.

Front 371

Which of the following air filters will efficiently remove large quantities of smoke and small particles in order to protect blowers?

fluidized-bed liquid filter
viscous impingement
electrostatic precipitators
dry-barrier

Back 371

electrostatic precipitators

Front 372

For most trickling filter systems, operators can use ___________ to control parameters such as the strength of the applied wastewater and the hydraulic loading to the filter.

polymer addition
clarifier wasting
the amount of underdrain
recirculation

Back 372

recirculation

Recirculation in trickling filter systems allow operators to control the strength of the wastewater being applied to the filter as well as allowing the operators to periodically gflushh the filter media by increasing the hydraulic load.

Front 373

Most often the RAS rate for an activated sludge process is based on ____________.

MCRT or SRT
influent BOD
disinfection requirements
coliform levels

Back 373

MCRT or SRT

The RAS rate is typically calculated as a percentage of a facilityfs influent flow based on a target mean cell residence time or solids retention time your facility requires. For example, the lower the MCRT required, the lower your RAS rate will need to be.

Front 374

LOX stands for ________________.

Liquid Oxygen
Light Oxygen Exchanger
Level Ozone Exchange
Low Oxygen

Back 374

Liquid Oxygen

LOX stands for liquid oxygen. It is one of the methods for supplying oxygen to high-purity oxygen activated sludge treatment facilities.

Front 375

In an activated sludge process, a reactor that is designed to have influent fed at 2 or more points along the length of the reactor is referred to as ___________.

plug-flow
step feed
sequential batch
oxidation ditch

Back 375

step feed

A step-feed activated sludge reactor is designed to have influent fed at 2 or more different points along the reactor length. This helps to evenly distribute the organic load or to adjust distribution if there is a problem with aeration in the reactor.

Front 376

At pH levels below __________, the activated sludge process will completely stop.

2.0
6.0
4.0
8.0

Back 376

2.0

For most activated sludge processes, a range of 6.5 to 8.5 must be maintained. If the process is nitrifying, a more stringent pH range of 7.0 to 8.0 is recommended. At pH levels below 2.0 and above 10.0, the activated sludge process will stop altogether.

Front 377

Ferric is typically supplied to wastewater treatment facilities as a _______________.

liquid
gas
powder
granules

Back 377

liquid

Due to its physical properties and storage requirements, ferric chloride is almost always supplied as a bulk liquid.

Front 378

The microorganisms typically involved in the activated sludge treatment are bacteria and protozoa such as _____________.

algae
fungi
rotifers
Nocardia

Back 378

rotifers

Rotifers are a type of protozoa useful to the activated sludge process. Algae and fungi are microscopic plants and Nocardia is detrimental bacteria.

Front 379

Thickening is primarily designed to reduce sludge _________.

solids
BOD
volume
organics

Back 379

volume

Thickening is primarily designed to reduce the volume of material to be removed or treated in downstream processes. It accomplishes this by removing water from sludge and thereby concentrating or thickening the sludge.

Front 380

Waste activated sludge is typically ___________ raw primary sludge.

the same as
more dense than
thinner than
thicker than

Back 380

thinner than

Typically the percentage of total solids in raw primary sludge is 3-4% while the percentage in waste activated sludge is 1-2%. Therefore it is thinner than raw sludge.

Front 381

Excess oil and grease in the influent will often lead to the formation of __________ in primary clarifiers.

foam
debris
floc
scum

Back 381

scum

Oil and grease often appear as scum in primary clarifiers. This scum is removed from the tanks using skimmers and should be removed from the treatment process and disposed of properly.

Front 382

Alum, ferrous sulfate, lime, ferric chloride, and polymers are chemicals used to precipitate_________ from wastewater.

phosphorus
grease
ammonia
bacteria

Back 382

phosphorus

Alum, lime, ferrous sulfate, ferric chloride, and organic polymers are chemicals used for precipitating phosphorus from wastewater.

Front 383

Tertiary wastewater treatment plants ________________.

use rotating biological reactors
use chemical precipitation and filtration
are less expensive than conventional secondary treatment plants
do not need disinfection

Back 383

use chemical precipitation and filtration

Tertiary treatment processes involve chemical-physical treatment of the wastewater. It utilizes processes such as chemical clarifiers and activated carbon filters for treatment.

Front 384

Chloramines are easily defined as _________________.

organic enzymes
disinfected organisms
free chlorine
chlorine combined with nitrogen compounds

Back 384

chlorine combined with nitrogen compounds

Chloramines are the combinations of chlorine and nitrogen compounds such as ammonia. Chloramines along with chloroorganics make up the combined chlorine residual.

Front 385

In an aerated lagoon, the minimum dissolved oxygen level that must be maintained is ________ ?

4 mg/L
3 mg/L
1 mg/L
2 mg/L

Back 385

1 mg/L

Typical practice is to maintain 1 to 2 mg/L DO in an aerated lagoon. A minimum of 1 mg/L should be kept during heavy loading periods.

Front 386

In an aerated lagoon, a minimum DO of 1.0 mg/L should be maintained during the highest demand period which usually occurs __________________.

in the morning
at noon
in the evening
at night

Back 386

at night

For aerated lagoons, highest oxygen demands usually occur at night when the algae are respiring.

Front 387

Chlorine gas is a hazardous material. Which of the following is a similar, but a safer, disinfection product?

Hydrogen sulfide
Sodium hypochlorite
Sulfur dioxide
Calcium dioxide

Back 387

Sodium hypochlorite

Sodium hypochlorite can be just as effective for effluent disinfection as chlorine and it is much less hazardous. However, it can be very expensive and, unlike chlorine, it has a limited storage period before it begins to degrade.

Front 388

Oxygen transfer is dependent upon

Back 388

the liquid temperature

Front 389

Which of the following provides an estimate of the quantity of solids to be wasted from an activated sludge aeration tank?

Back 389

The rate of settling and settleometer reading

Front 390

Flagellates predominate in a system with a low bacteria population and a high organic load. The floc is light and dispersed. The process change needed to keep the light, dispersed floc from becoming a problem is to

Back 390

increase the mcrt

Front 391

pin floc is present in the effluent of a conventional activated sludge plant. The mixed liquor settling test shows rapid settling and cloudy supernatant.

Back 391

Increase the WAS rate.

Front 392

Based on the results shown in the table below, if no process changes are made, the expected results in the aeration tank are:

influent cbod & tss

month 1 200 mg/l, 150

month 2 550 mg/l, 600

Back 392

Mlss and cbod increase; DO decrease

Front 393

Compared to normal operating results, you observe a steady increase in oxygen uptake rate from your aeration tank effluent sample. This indicates

Back 393

There is a need to increase your mlss concentration

Front 394

What is indicated if a mixed liquor sample from an activated sludge process has large number of amoebas and other flagellated protozoa.

Back 394

young sludge

Front 395

Which of the following bod:n:p ratios represents a nitrogen deficiency?

Back 395

200:5:2

Front 396

What should the bod:n:p ratio be?

Back 396

100:5:1

Front 397

micro organisms that obtain carbon from organic matter for the synthesis of cell tissue are called

Back 397

heterotrophic

Front 398

micro organisms that obtain carbon from inorganic matter and sunlight

Back 398

autotrophic

Front 399

micro organisms that nitrify are

Back 399

autotrophic

Front 400

When there are a large amount of micro organisms and very little food or BOD, they will not reproduce as much but will keep using oxygen to metabolize food stored in cells. This is called

Back 400

endogenous respiration

Front 401

When collecting nocardia samples where is it highly concentrated?

Back 401

in the foam

Front 402

a properly operating activated sludge plant normally has a mixed liquor which contains what percent volatile solids?

Back 402

70-80%

Front 403

In a biological nutrient removal system in which phosphorus removal has declined, it is appropriate to test the mixed liquor in the anaerobic zone for the presence of

Back 403

nitrates

Front 404

Which activated sludge process would handle shock loads of organics most effectively?

Back 404

step feed

Front 405

When used for disinfection ozone is generated on-site because

Back 405

ozone is unstable

Front 406

Three forms of alkalinity

Back 406

bi-carbonate, hydroxide, carbonate

Front 407

Max storage time for a BOD sample?

Back 407

48 hrs

Front 408

Which of the following describes the best way to remove calcium deposits from a hypochlorite solution feed pump?

Back 408

an acid solution to dissolve the calcium deposits

Front 409

cod test results are obtained by a strong chemical procedure

Back 409

oxidation

Front 410

After dechlorinating a BOD sample, what would you do next?

Back 410

Seed the sample

Front 411

Samples for fecal coliform tests should be incubated at

Back 411

44.5 C

Front 412

Samples for E. Coli MPN should be incubated at

Back 412

35C

Front 413

Which of the following samples cannot be preserved by cooling alone prior to analysis?

Back 413

COD

Front 414

What is the chlorinator withdrawing if it is connected to the bottom valve of a half full 1-ton cylinder?

Back 414

liquid chlorine

Front 415

Proper sample container for an oil and grease sample is

Back 415

wide mouth glass bottle

Front 416

what's the normal average contact time required for a chlorination system

Back 416

30-60 min

Front 417

The dilution water used in a BOD test should have an initial dissolved oxygen content of about

Back 417

7-9 mg/L

Front 418

Which acid is used to lower the pH less than 2 for a sample collected for COD analysis?

Back 418

sulfuric acid

Front 419

total toxic organics include

Back 419

chlorinated hydrocarbons

Front 420

What chemicals reduce or eliminate chlorine residual?

Back 420

sulfur dioxide and sodium metabisulfite

Front 421

What happens during breakpoint chlorination

Back 421

ammonia-nitrogen is oxidized to nitrogen gas

Front 422

What disinfection system produces the fewest disinfection by products?

Back 422

UV

Front 423

When fecal coliform samples are preserved at 10C or less, what's the max allowable time between collecting and testing?

Back 423

6 hours

Front 424

Glassware used for phosphorus testing must be

Back 424

rinsed with hydrochloric acid and distilled water

Front 425

Biosolids records must be kept for how long?

Back 425

5 yrs

Front 426

In the endogenous respiration phase, the mass of bacteria

Back 426

Decreases

Front 427

What's an advantage of aerobic digestion compared to anaerobic digestion?

Back 427

Close operational control of the VA/ALK relationship is not necessary

Front 428

CFR 503 says that sour must be less than

Back 428

1.5 mg/hour/gram

Front 429

In an anaerobic digester gas pressure is maintained by a controlling mechanism that is commonly regulates

Back 429

6-8 inches of water column pressure

Front 430

Thermophilic bacteria thrive at temperatures

Back 430

above 45 degrees C

Front 431

When first starting up a DAF unit the operator should

Back 431

close all the drain line valves from all the tanks, compartments, and the dump valves within the system

Front 432

If an anaerobic digester starts foaming what should you do

Back 432

reduce feed rate and monitor ph, add alkalinity if needed

Front 433

Buffer capacity in an anaerobic digester is measured by

Back 433

alkalinity

Front 434

What gases are produced in the highest concentrations during the initial start up of an anaerobic digester?

Back 434

Carbon dioxide and hydrogen sulfide

Front 435

During aerobic digestion, why does the pH in the digester decrease?

Back 435

Utilization of alkalinity

Front 436

What will most likely occur if sludge is pumped to a vacuum filter faster than it is being dewatered by the filter?

Back 436

filter vat will probably overflow onto the floor

Front 437

how can stack gases from a sludge incinerator be deodorized?

Back 437

raise the temperature of the gases sufficiently so that they burn

Front 438

a concentration of _____percent digester methane gas in air is explosive

Back 438

5-15%