Wisconsin Advanced General Wastewater Stude Guide

Front 1

Define: Influent

Back 1

Wastewater entering a treatment plant (raw sewage).

Front 2

Define: Effluent

Back 2

Treated wastewater discharged from a treatment plant to the enviroment.

Front 3

Define: Biochemical Oxygen Demand (BOD)

Back 3

A test that measures the organic strenght of a sample by measuring the amount of oxygen consumed.

Front 4

Define: Total suspended solids

Back 4

A test that measures the total amount of solids suspended in a sample.

Front 5

Define: pH

Back 5

A measure of the acidicty or alkalinity of a sample on a scale of 0-14. pH 7 is neutral.

Front 6

Define: Disolved Oxygen

Back 6

A measure of the amount of oxygen dissolved is water.

Front 7

Define: Gallons per Minute (GPM)

Back 7

The number of gallons flowing each minute.

Front 8

Define: Gallons per Day (gpd)

Back 8

The number of gallons flowing each day.

Front 9

Define: Million Gallons per Day (MGD)

Back 9

The number of gallons flowing each day, expressed as millions of gallons.

Front 10

Define: Milligrams per Liter (mg/L)

Back 10

The concentration of a substance in a liquid expressed as a weight in milligrams per liter of a volume (mg/L). Milligrams per liter is the same as parts per million (ppm)

Front 11

Define: Composite Sample

Back 11

A sample prepared by combining a number of grab samples, typically over a 24 hour period.

Front 12

Define: Grab Sample

Back 12

A single sample taken at a particular time and place that is representative of the current conditions.

Front 13

Define: Weir

Back 13

A level control structure used to provide uniform flow.

Front 14

Define: Flume

Back 14

A restriction in an open channel used to measure flow.

Front 15

Define: Septage

Back 15

A high strength waste pumped out of septic tanks, sometimes disposed at WWTPs.

Front 16

Define: Hydraulic Retention Time (HRT)

Back 16

The period of time that wastewater remains in a tank. This term is also known as detention time.

Front 17

Define: Eutrophication

Back 17

The process of excessive growth of plant and algae in receiving waters due to dissolved nutrients and their decomposition.

Front 18

Define: Sludge Age

Back 18

The theoretical length of time a particle of activated sludge stays in the treatment plant, measured in days. In an activated sludge plant, sludge age is the amount (lbs) of mixed liquor suspended solids divided by the suspended solids, or excess cell mass, withdrawn from the system per day (lbs per day of waste activated sludge).

Front 19

Define: Food to microorganism ratio (F:M or F/M)

Back 19

The amount of food (BOD) provided to the microorganisms (MLVSS or MLSS) in the aeration basins.

Front 20

Define: Inflow/Infiltration (I/I)

Back 20

Any unwanted clearwater that leaks into a collection system. Generally it consists of groundwater, rainwater, or snowmelt.

Front 21

Define: Sanitary Sewer (Collection System)

Back 21

An underground pipe system used to convey wastewater to a treatment facility.

Front 22

Define: Storm Sewer

Back 22

An underground pipe system that collects rainwater from streets and conveys it to a place other than the wastewater treatment plant.

Front 23

Define: Combined Sewer

Back 23

Pipe conveyances that carry both wastewater and storm water in a single pipe. During dry weather conditions, combined sewers discharge to a wastewater treatment plant. During wet weather conditions, combined sewers used to discharge directly to a water body; now the extra wet weather volume is stored until it can be returned to the wastewater treatment plant.

Front 24

Define: Lift Station

Back 24

An underground chamber with pumps that is used to elevate (lift) wastewater to a higher grade. Lift stations are located within a collection system.

Front 25

Define: Manhole

Back 25

A manhole is a structure that provides access to a sewer system. They usually are a round opening with an iron lid.

Front 26

Define: Wet Well

Back 26

A tank where wastewater is collected. The wastewater is then pumped from the wet well. Wet wells are commonly found in lift stations and at the headworks of the wastewater treatment plant.

Front 27

Define: Sanitary Sewer Overflow (SSO)

Back 27

The release of wastewater from a sewage collection system or an interceptor sewer directly into a water of the state or to the land surface. It is commonly referred to as a "SSO".

Front 28

Define: Microorganism

Back 28

A living organism too small to be seen with the naked eye but is visible under a microscope such as a bacteria, viruses, fungi, or protozoa.

Front 29

Define: Sidestreams

Back 29

A flow generated within the plant, usually from solids processing, that then is recycled back through the plant.

Front 30

Define: Aerobic (oxic) [O2]

Back 30

A condition in which free and dissolved oxygen is available in an aqueous environment.

Front 31

Define: Anaerobic (septic) [Ø]

Back 31

A condition in which free, dissolved, and combined oxygen is unavailable in an aqueous environment.

Front 32

Define: Anoxic

Back 32

A condition in which oxygen is only available in a combined form such as nitrate (NO3-), nitrite (NO2-), or sulfate (SO4-2) in an aqueous environment.

Front 33

Define: Treatment Process

Back 33

A physical, biological, or chemical action that is applied to wastewater to remove or reduce pollutants.

Front 34

Define: Treatment Unit

Back 34

A treatment unit is an individual structure or equipment within a sewage or wastewater treatment facility that is part of a treatment process.

Front 35

Define: Selector

Back 35

Part of the treatment system that selects for a specific type of microorganism by providing an environment (anaerobic, anoxic, aerobic) that favors its growth.

Front 36

Define: Preliminary Treatment

Back 36

A treatment process consisting of screening and grit removal before the wastewater flows on to other treatment processes.

Front 37

Define: Primary Treatment

Back 37

A treatment process that usually consists of clarification by solid-liquid separation that removes a substantial amount of suspended and floating matter.

Front 38

Define: Secondary Treatment

Back 38

A treatment process that uses biological processes utilizing bacteria to remove pollutants.

Front 39

Define: Tertiary Treatment

Back 39

A wastewater treatment process that uses physical, chemical, or biological processes to remove suspended solids and nutrients to a level that is greater than what can be achieved by secondary treatment.

Front 40

Define: Headworks

Back 40

Headworks is the beginning, or head, of a treatment plant where influent flow is measured and sampled and where preliminary treatment occurs.

Front 41

Define: Grit

Back 41

The fine abrasive particles removed from wastewater, such as sand and eggshells.

Front 42

Define: Screenings

Back 42

The materials in wastewater that are removed on screens at the headworks of treatment plants, such as sticks, stones, plastics, and personal hygiene products.

Front 43

Define: Aeration Basin

Back 43

A tank in which wastewater is aerated to achieve biological treatment.

Front 44

Define: Clarifier

Back 44

A circular or rectangular tank used to remove floatable and settleable solids in wastewater.

Front 45

Define: Disinfection

Back 45

A process used to destroy most pathogens in the effluent to a safe level. Disinfection does not destroy all microorganisms.

Front 46

Define: Biosolids

Back 46

The nutrient-rich, organic byproduct of a wastewater treatment plant that is utilized as fertilizer.

Front 47

Define: Process Control

Back 47

The tools and methods used to optimize treatment plant operations.

Front 48

Define: Return Activated Sludge (RAS)

Back 48

The settled activated sludge (biomass) that is collected in a secondary clarifier and returned to the secondary treatment process to mix with incoming wastewater. This returns a concentrated population of microorganisms back into the aeration basin.

Front 49

Define: Waste Activated Sludge (WAS)

Back 49

The activated sludge (excess biomass or cell mass) removed from the secondary treatment process. For most treatment plants, this will be a portion of the Return Activated Sludge (RAS) flow stream.

Front 50

Define: Confined Space

Back 50

A space that is large enough for an operator to enter and perform assigned work. It has limited or restricted means for entry or exit and is not designed for continuous occupancy.

Front 51

Define: Pathogens

Back 51

Infectious microorganisms in wastewater that pose health risks.

Front 52

Define: Wisconsin Pollutant Discharge Elimination System (WPDES) Permit

Back 52

This permit is issued to wastewater facility owners, and contains facility effluent and biosolids/sludge limitations, conditions, and reporting requirements.

Front 53

Where a wastewater treatment plant operator would find information on conducting
wastewater tests.

Back 53

Standard Methods for the Examination of Water and Wastewater, prepared and published jointly by the American Public Health Association, American Water Works Association and Water Environment Federation.

Commonly referred to simply as Standard Methods.

Front 54

Standard Methods for the Examination of Water and Wastewater was first published in what year?

Back 54

1905

Front 55

Describe the characteristics of influent domestic wastewater.

Back 55

Sewage is >99% water. It is gray in color and has an earthy, musty odor.

Front 56

Typical influent wastewater concentrations of BOD are?

Back 56

250 mg/L

Front 57

Typical influent wastewater concentrations of TSS are?

Back 57

300 mg/L

Front 58

Typical influent wastewater concentrations of Total Nitrogen are?

Back 58

40 mg/L

Front 59

Typical influent wastewater concentrations of Ammonia are?

Back 59

25 mg/L

Front 60

Typical influent wastewater concentrations of Total Phosphorus are?

Back 60

9 mg/L

Front 61

Typical influent wastewater concentrations of Fats, Oil, and Grease (FOG) are?

Back 61

100 mg/L

Front 62

Typical influent wastewater pH is?

Back 62

6.5 - 8.0

Front 63

The most authoritative source for conducting wastewater testing can be found in

Back 63

Standard Methods for the Examination of Water and Wastewater

Front 64

A wet well lift station is a

Back 64

single chamber that collects wastewater.

Front 65

pump and motor being completely submerged in the wetwell.

Back 65

submersible lift station

Front 66

The submersible centrifugal pump is

Back 66

watertight, and normally controlled by float switches.

They are made to be easily removed for cleaning and
maintenance using a rail system.

Front 67

In wetwell/drywell lift stations

Back 67

the centrifugal pumps and other equipment are located in a separate chamber (drywell), with only the suction pipe being submersed in the wetwell.

Front 68

One of the main reasons sewers back-up and overflow is

Back 68

too much clearwater gets into the sewer pipes through
infiltration or inflow (I/I) during wet weather events

Front 69

Sewer pipes are designed for

Back 69

only a certain flow capacity and excessive I/I can exceed that capacity

Front 70

As sewers age

Back 70

sewer defects increase, allowing for more clearwater (I/I) to get into them

Front 71

circumstances that
can cause an overflow are power outages

Back 71

plugged sewers due to grease or large objects, broken or collapsed pipes, equipment failure such as a lift station pump, or widescale flooding.

Front 72

Some dairy operations have their own

Back 72

wastewater treatment plant but many discharge to the wastewater treatment plant in the community they are located

Front 73

Industrial wastes from dairy facilities consist of

Back 73

various dilutions of milk that enter the municipal sewage system

Front 74

One of the largest sources of dairy wastewater come from

Back 74

washwaters and rinse waters of dairy tanks, trucks, equipment, pipelines, and floors

Front 75

Dairies use clean-in-place (CIP) systems

Back 75

that alternate acid and caustic cleaners and rinses in the cleaning of tanks, equipment, and pipes

Front 76

dairy wastewater pH

Back 76

can be high or low

Front 77

Milk and milk solids

Back 77

have a very high biochemical oxygen demand (BOD). BODs can range from 1,000-10,000 mg/L.

Front 78

Milk wastes contain

Back 78

high amounts of nitrogen, phosphorus, and chlorides.

Front 79

collection and equalization of dairy wastewater is

Back 79

very important so that the flow and BOD discharges to the sewer system are more uniform

Front 80

A wastewater treatment plant can be upset if

Back 80

it receives variable loads, high strength wastes, high or low pH discharges, or slug loads from a dairy facility.

Front 81

Food (meats, canned foods, snacks, etc) is processed in many different ways and the wastes from them

Back 81

are usually high in BOD, suspended solids, nitrogen compounds, phosphorus, chlorides, and vary in pH

Front 82

Brewery wastewater typically has a

Back 82

high concentration of biochemical oxygen demand from the carbohydrates and protein and in the cleaning of vessels, pipes, and equipment.

Front 83

Brewery wastewater can have a BOD of

Back 83

1,000-4,000 mg/L,

Front 84

Brewery wastewater can have a TSS of

Back 84

200-1,000 mg/L

Front 85

Brewery wastewater can have a Nitrogen of

Back 85

25-80 mg/L

Front 86

Brewery wastewater can have a Phosphorus of

Back 86

1-50 mg/L

Front 87

Brewery wastewater can have a pH of

Back 87

4-12.

Front 88

Metal finishing wastewater

Back 88

has very little BOD associated with it, but has pollutants that can be toxic to fish and aquatic life, even in small concentrations, as well as wastewater treatment plant microorganisms.

Front 89

Metal finishing wastewater

Back 89

can contain phosphates and toxic materials such as
chromate, cyanide and metals.

Front 90

Many metal finishing industries have federal or state pretreatment requirements before

Back 90

they can discharge their waste to a sanitary sewer
system

Front 91

Metals can concentrate in treatment plant sludges and therefore metals in sludges must be analyzed and reported to

Back 91

the DNR on sludge characteristic reports

Front 92

Sludge with high metals concentrations are prohibited

Back 92

or restricted in the rate of application due to potential toxicity and/or soil accumulation concerns.

Front 93

Cleaning products

Back 93

They are important in ensuring public health

Front 94

used frequently and in large quantities at

Back 94

industries, businesses, schools, nursing homes, medical facilities, or restaurants

Front 95

Many effective cleaners contain

Back 95

phosphates and thus can contribute a lot of phosphorus to wastewater.

Front 96

quaternary ammonium compounds (commonly known as "quats")

Back 96

can have toxic effects at a treatment plant.

Front 97

Ammonia-based cleaning products

Back 97

contribute ammonia to the wastestream, which will need to be removed since ammonia can be toxic to fish and aquatic life.

Front 98

Surfactants can interfere and

Back 98

keep solids from settling in clarifiers as well as create foam in aeration basins

Front 99

Fats, oils, and grease are

Back 99

found in meats, dairy products, cooking oils, shortenings, food scraps, and sauces.

Front 100

The most common cause of sewage overflows from sewer
pipes are

Back 100

blockages caused by grease

Front 101

If grease makes its way to the treatment plant, it can

Back 101

plug valves, meters and pipes at the plant.

It floats to tank surfaces and can create
settling problems.

Front 102

Grease can favor growth

Back 102

of filamentous organisms that create surface foam and scum

Front 103

The best practice for controlling grease

Back 103

is keeping it out of the sewer system in the first place by having a Grease Control Program in a community

Front 104

A Grease Control Program usually involves

Back 104

regular inspections of restaurant and institutional (nursing home, hospital, and school kitchens) grease traps or interceptors and an ongoing information & education program with residents and businesses.

Front 105

Volatile organics

Back 105

such as gasoline or solvents that can cause an explosive atmosphere in the sewer system or at the treatment plant.

Front 106

Heavy metals

Back 106

such as chromium, zinc, copper, nickel, and cadmium are very toxic and can cause a treatment plant upset, pass through the plant or accumulate in the sludge.

Front 107

Acidic and alkaline wastes can

Back 107

damage the sewer system or upset the treatment plant. Generally, pH's lower than 5.0 or greater than 10.0 should be neutralized prior to discharge to the sewer system.

Front 108

Fats, Oils, and Grease (FOG)

Back 108

must be controlled at industrial and commercial sources with oil separators and grease traps to prevent maintenance problems in wet wells and at the treatment plant.

Front 109

High strength loadings of BOD or suspended soils

Back 109

could organically overload the treatment plant. This would especially be a problem with "batch" dumping that would cause large slug loads. Any "batch" type operation should be handled by flow equalization to prevent plant upsets.

Front 110

High temperature wastewaters

Back 110

could affect biological activity

Front 111

solid or viscous materials

Back 111

could cause sewer blockages

Front 112

debris such as rags or other materials

Back 112

could cause sewer blockages or pump clogging.

Front 113

While flow monitoring is required in WPDES permits for measuring

Back 113

influent and effluent flows

Front 114

In an activated sludge plant, measuring

Back 114

return and waste activated sludge is extremely important as they are the key to successful operations

Front 115

In-plant flow meters are used for measuring

Back 115

A. Return activated sludge (RAS)
B. Waste activated sludge (WAS)
C. Recycle or recirculation flows
D. Sidestream flows
E. Sludge flows to digesters
F. Sludge feed rates to sludge dewatering equipment
G. Sludge withdrawal volumes from storage tanks

Front 116

Flow proportional sampling is

Back 116

the most representative method of collecting wastewater samples for wastewater coming into and being discharged from a treatment plant on a continuous basis.

Front 117

For most treatment plants in Wisconsin, flow proportional sampling is

Back 117

a permit requirement

Front 118

The sampler is programmed to collect a certain sample volume per

Back 118

unit volume of flow (flow pulse interval)

Front 119

It is better to take a small sample

Back 119

more often than it is to take a large sample less often

Front 120

As a starting point in programming the sampler correctly,

Back 120

make sure a sample is collected at least every 10-15 minutes (4-6 samples every hour) during the peak flow period of the day

Front 121

if a peak hourly flow of 60,000 gallons flows into the plant between 8 am - 9 am, the sampler should be programmed

Back 121

take a sample every 10,000-15,000 gallons of flow (60,000 gallons per hour/6 samples per hour = 10,000 gallons/sample).

Front 122

The volume of sample collected each flow pulse interval should be

Back 122

to fill at least 1/4 to 1/2 of the compositing container in 24 hours during average flows.

Front 123

A flow proportional sample

Back 123

MUST sample during a full 24 hour period, even during wet weather peak flows.

Front 124

The purpose of preliminary treatment is

Back 124

to remove larger materials (rags, sticks, stones, plastics, personal hygiene products, etc.) and grit from the wastestream before it flows to downstream treatment units.

Front 125

Preliminary treatment equipment primarily consists

Back 125

of screening and grit removal systems. Septage handling, grinders, odor control, and flow equalization are also considered preliminary treatment.

Front 126

Common screening systems are

Back 126

manually cleaned bar screens, mechanically cleaned bar screens, and rotary fine screens. These processes simply remove debris which is then land filled.

Front 127

Common grit removal systems are

Back 127

aerated grit chambers and vortex-type (Pista®). An aerated grit chamber uses air that separates light from heavier solids (grit). A vortex-type (Pista®) unit consists of cylindrical tank creating a vortex flow in which the heavier grit settles to the bottom.

Front 128

how an aerated grit chamber works

Back 128

Raw wastewater is introduced into the end of an aerated grit chamber, which is typically rectangular in shape. Injected air creates a spiral flow of wastewater as it moves through the chamber. As the flow velocity diminishes along the tank, heavier grit particles gradually settle from the water. The settled solids are typically gathered at the tank bottom by a rake mechanism and removed by pumping.

Front 129

how a vortex-type (Pista®) grit chamber works

Back 129

Raw wastewater is introduced along the side of a cylindrical tank designed for vortex flow. The water and grit combination rotates slowly around the vertical access of the tank. The flow spirals gradually down the tank perimeter, allowing the heavier solids to settle to the tank bottom where they are then removed.

Front 130

Common primary treatment units are

Back 130

rectangular clarifiers, circular clarifiers, and dissolved
air flotation.

Front 131

The purpose of primary treatment is to

Back 131

settle wastewater solids and capture floatable substances (such as oil & grease).

Front 132

Well designed and operated primary facilities

Back 132

can expect removal efficiencies of 60-75% for suspended solids and 20-35% for BOD.

Front 133

The purpose of secondary biological treatment

Back 133

is to remove dissolved and suspended organic material from wastewater to produce an environmentally-safe treated effluent and biosolids/sludge.

Front 134

A secondary treatment system can

Back 134

achieve overall BOD and suspended solids removal in the 85-95% range.

Front 135

Common equipment used in suspended growth secondary biological treatment are

Back 135

aeration tanks, blowers, diffusers, final clarifiers, and sludge pumps.

Front 136

Aeration tanks are usually

Back 136

square, rectangular, or circular

Front 137

Aeration tanks contain

Back 137

aeration equipment for providing oxygen to the microorganisms that live and grow in the tanks

Front 138

Aeration equipment

Back 138

provides mixing in the tank

Front 139

The mixed suspension of sewage, solids, and microorganisms in the aeration tank is commonly referred to as

Back 139

activated sludge

Front 140

activated sludge is measured as mixed liquor suspended solids in

Back 140

milligrams per liter (mg/L)

Front 141

Diffusers disperse the air into the aeration tank

Back 141

providing oxygen and mixing in the tank.

Front 142

Final clarifiers follow the aeration basins and

Back 142

settle the mixed liquor suspended solids.

Front 143

Clear effluent is discharged over and through weirs in

Back 143

final clarifiers

Front 144

The settled solids in the clarifier can be returned back to the aeration tank or wasted from the treatment system by a pump(s). The pump(s) are known as

Back 144

return activated sludge (RAS) or waste activated sludge (WAS) pump(s)

Front 145

Common equipment used in attached growth systems such as trickling filters and biotowers are

Back 145

different types of media, pumps, distribution arm and
piping, and underdrains

Front 146

Common equipment used in attached growth systems such as rotating biological contactors are

Back 146

basins, shafts, circular plastic disks, motors, and drives and sometimes blowers/diffusers (for air driven shafts).

Front 147

After wastewater receives primary treatment, primary effluent is collected and pumps are used to convey the wastewater to

Back 147

a trickling filter, a biotower distribution arm, or to RBC
basins for secondary biological treatment.

Front 148

The media is the place where biological organisms and bacteria

Back 148

attach themselves for treatment of the incoming wastewater

Front 149

Trickling filter media most commonly consists of

Back 149

bed of rocks, gravel, or plastic through which the wastewater flows

Front 150

Rotating biological contactors (RBC) consist of

Back 150

closely spaced, circular plastic disks that rotate on a shaft
through the wastewater.

Front 151

After wastewater flows down through a trickling filter or biotower, it is

Back 151

collected through a drain where some of it is recirculated back through the media by pumps for further treatment

Front 152

temperature difference between outside air temperature and the temperature inside the filter

Back 152

natural air drafts upward through the filter media, providing oxygen.

Front 153

The circular plastic disks of RBCs

Back 153

are on a shaft that is turned by a motor/drive system.

Front 154

Used to monitor aeration basin dissolved oxygen levels

Back 154

Dissolved Oxygen Meter

Front 155

Many plants have in-line dissolved oxygen sensors to

Back 155

automatically control DO levels

Front 156

Used to monitor sludge settling characteristics in 30 minutes

Back 156

Settleometer

Front 157

Settleometer, A ______ mL beaker or cylinder is most commonly used.

Back 157

1000

Front 158

The mixed liquor suspended solids sample for a Settleometer test should be collected

Back 158

just before it goes to the final clarifier.

Front 159

Used to measure the depth of settled sludge in the bottom of a clarifier

Back 159

Sludge Blanket Finder

Front 160

Used to observe the population and health of microorgansims living in an activated sludge
system

Back 160

Microscope

Front 161

Used to measure pHs and temperatures of wastewater entering the plant and the aeration
basins.

Back 161

pH/Temperature Meter

Front 162

Used to measure influent, sidestream, RAS, WAS, and effluent flows.

Back 162

Flow Meters

Front 163

Nitrification

Back 163

is a biological process where nitrifying bacteria convert nitrogen in the form of ammonia (NH3) into nitrite (NO2-) and nitrate (NO3-) under aerobic conditions

Front 164

Treatment plants that have ammonia limits will use

Back 164

nitrification to remove ammonia

Front 165

Many plants that discharge to surface waters have ammonia limits

Back 165

to protect fish and aquatic life from ammonia toxicity.

Front 166

Denitrification

Back 166

is a biological process where bacteria convert nitrate (NO3-) and nitrite (NO2-) to nitrogen gas (N2) under anoxic conditions

Front 167

Treatment plants that have total nitrogen limits will use

Back 167

denitrification to remove nitrogen

Front 168

Plants that discharge to groundwater have total nitrogen limits

Back 168

to protect groundwater from nitrates

Front 169

Plants that remove phosphorus biologically will also employ denitrification

Back 169

to remove nitrates that interfere with biological phosphorus removal

Front 170

Ammonia is toxic to fish and aquatic life and its toxicity is temperature

Back 170

and pH dependent

Front 171

limits for ammonia nitrogen are calculated based on

Back 171

stream flow, stream temperature, stream pH, and the type of fishery classification

Front 172

Phosphorus is one of the key nutrients that contribute to

Back 172

eutrophication and excess algae/plant growth in rivers and lakes.

Front 173

decomposition of excess plant matter may

Back 173

reduce the level of dissolved oxygen in the receiving water which affects aquatic life

Front 174

The principle role microorganisms have in the activated sludge process is

Back 174

to convert dissolved and particulate organic matter, measured as biochemical oxygen demand (BOD), into cell mass

Front 175

In a conventional activated sludge process

Back 175

microorganisms use oxygen to break down organic matter (food) for their growth and survival

Front 176

In a conventional activated sludge process, over time and as wastewater moves through the aeration basin

Back 176

food (BOD) decreases with a resultant increase in cell mass (MLSS concentration).

Front 177

The activated sludge wastewater treatment process must operate under proper environmental conditions

Back 177

to support a healthy, growing population of microorganisms.

Front 178

The operator must monitor the activated sludge process to

Back 178

ensure the right environmental conditions are being provided for the microorganisms.

Front 179

Incoming wastewater to a treatment plant provides the food that microorganisms

Back 179

need for their growth and reproduction

Front 180

The more soluble the organic material is

Back 180

the more easily microorganisms can use it

Front 181

Since the amount and type of organic loading in the treatment plant affects the growth of the microorganisms

Back 181

influent total BOD and soluble BOD are measurements an operator can make to determine the amount and type of incoming food for the microorganisms

Front 182

Incoming wastewater must flow through a treatment plant at a rate that allows

Back 182

microorganisms sufficient time to consume the incoming food and to settle properly

Front 183

High flows can shorten

Back 183

the time necessary for the full treatment of wastewater

Front 184

Extremely high flows can wash

Back 184

microorganisms out of the plant through the final clarifier

Front 185

Conventional activated sludge is an

Back 185

aerobic process

Front 186

Many bacteria in the activated sludge process need

Back 186

free oxygen (O2) to convert food into energy for their growth

Front 187

For optimal performance, it is very important for an operator to be sure enough oxygen is being provided in the

Back 187

aeration tanks for the microorganisms (typically 1.0-3.0 mg/L)

Front 188

Aeration basin dissolved oxygen concentrations (milligrams per liter)

Back 188

typically 1.0-3.0 mg/L

Front 189

Aeration basin dissolved oxygen concentrations

Back 189

are measured continuously in many plants to ensure adequate oxygen is available.

Front 190

All biological and chemical reactions are affected by

Back 190

temperature

Front 191

Microorganisms' growth and reaction rates are slow

Back 191

at cold temperatures

Front 192

Microorganisms' growth and reaction rates are much faster

Back 192

at warmer temperatures

Front 193

Most microorganisms do best under moderate temperatures

Back 193

(10-25 ºC)

Front 194

Most microorganisms do well in a pH environment between

Back 194

6.0-9.0

Front 195

Acidic (low pH) or alkaline (high pH) conditions can adversely affect

Back 195

microorganism growth and survival

Front 196

Operators measure both influent pH and aeration
basin pH

Back 196

to ensure proper plant pH conditions

Front 197

Microorganisms need trace nutrients such as

Back 197

nitrogen, phosphorus, and some metals for their metabolism

Front 198

The ratio of BOD5 to nitrogen (N) to phosphorus (P)

Back 198

should be at least 100:5:1

Front 199

Depending on the concentration of toxic material

Back 199

microorganisms could be destroyed or their metabolic rates affected, thus impairing the
wastewater treatment plant efficiency

Front 200

The secondary clarifier is a large basin or tank designed to

Back 200

allow organic solids to settle from effluents discharged from trickling filters, rotating biological contactors (RBC’s), and/or the activated sludge process

Front 201

Hydraulic overloads or operational problems in the secondary system can cause

Back 201

major problems in the efficiency of the secondary clarifier,
because the biologic solids to be removed have a density very close to that of water

Front 202

The purpose of final clarification is to

Back 202

settle secondary biological treatment solids and discharge clear effluent.

Front 203

Motor and Drive System

Back 203

The device used to turn the surface skimmer and sludge collector.

Front 204

Center Stilling Well

Back 204

The suspended column in the center of a clarifier which provides an area for mixed liquor flow to slow down and spread out.

Front 205

Scum Skimmer

Back 205

C. Scum Skimmer The flat device at the surface of the clarifier which is moved by the drive system, to remove
floating scum.

Front 206

Scum Beach/Trough

Back 206

The equipment used to receive the collected scum.

Front 207

Scum Baffles

Back 207

The ring or plate at the clarifiers surface that prevents scum from entering the effluent trough

Front 208

Effluent Weirs

Back 208

Weirs that rest just below the clarifier surface which allows effluent to flow over and through
into the trough

Front 209

Effluent Trough

Back 209

The open channel on which the effluent weir is mounted and conveys the effluent

Front 210

Sludge Collection and Removal Mechanism

Back 210

The assembly and piping arrangement at the bottom of the clarifier which is moved by the drive system and used to gather and remove settled sludge.

Front 211

RAS/WAS Pump

Back 211

A pump that returns or wastes the settled solids from the final clarifier

Front 212

The purpose of tertiary treatment is to

Back 212

provide advanced wastewater treatment beyond secondary biological treatment when the need to meet stringent effluent limits is required

Front 213

the most common method of tertiary treatment is

Back 213

filtration

Front 214

The overall efficiency in removing pollutants by filtration

Back 214

could exceed 95% removal of suspended solids and phosphorus

Front 215

less used methods of tertiary treatment are

Back 215

carbon adsorption and physical-chemical methods.

Front 216

The filtering of very fine suspended particles in the effluent is accomplished using

Back 216

sand or mixed media, cloth or membranes, depending on the level of tertiary treatment needed

Front 217

As fine particles are filtered from the wastewater, eventually the particles start to plug the filter media and

Back 217

cleaning becomes necessary

Front 218

Backwashing sand filters or cloth disks is done to

Back 218

re-open the filtering pore space to restore the performance of the filter

Front 219

Membranes are subject to fouling and

Back 219

are cleaned in using one or a combination of a variety of these methods; backwashing, air sparging, relaxation and chemical clean-in-place

Front 220

The purpose of disinfection of treated wastewater is to

Back 220

kill and thus reduce the discharge of waterborne pathogenic organisms that cause illness, as the final step of the treatment processes

Front 221

Prior to disinfection, wastewater must be treated through

Back 221

the headworks, aeration basins, and final clarifiers.

Front 222

Common disinfection processes used are

Back 222

chlorination and ultraviolet (UV) radiation.

Front 223

The process of chlorination uses

Back 223

chlorine as a gas, solid, or as a liquid

Front 224

Chlorine contact tanks gives

Back 224

time for the chlorine to react with the wastewater killing the pathogenic organisms

Front 225

is added to remove the excess chlorine

Back 225

sodium bisulfite or sulfur dioxide)

Front 226

Chemical feed pumps that are flow proportional are

Back 226

commonly used in feeding liquid chlorine

Front 227

When feeding chlorine as a gas

Back 227

special equipment is used that creates a vacuum which draws the gas into the treated wastewater

Front 228

The process of UV radiation use

Back 228

ultraviolet light to destroy the pathogenic organism’s
ability to reproduce

Front 229

The purpose of pond and lagoon systems are to

Back 229

accomplish secondary biological treatment in an economical way.

Front 230

Ponds are lined with

Back 230

a clay or synthetic liner to prevent leakage to groundwater

Front 231

Wastewater is pumped into one end of the pond. On the other end the flow exits through a

Back 231

control manhole, which may consist of stop logs or a telescopic valve, allowing the operator to control the pond depth

Front 232

Most stabilization pond systems have a detention time

Back 232

150 days or greater and use more than one pond to effectively treat the wastewater

Front 233

Aerated lagoons can use surface aerators or

Back 233

subsurface diffusers to provide aeration and mix the wastewater

Front 234

Aerated lagoons are usually deeper and

Back 234

have shorter detention times(60 days) to effectively treat the wastewater

Front 235

Photosynthesis is a chemical process in nature in which

Back 235

green plants (algae in ponds) that contain chlorophyll use carbon dioxide in the presence of sunlight to produce carbohydrates to grow

Front 236

In wastewater treatment ponds, photosynthesis releases

Back 236

oxygen as a byproduct, providing oxygen to the bacteria that stabilize the suspended organic material in wastewater

Front 237

Photosynthesis can be summarized by the equation:

Back 237

Carbon dioxide + Water => Carbohydrate + Water + Oxygen

Front 238

Photosynthesis can be summarized by the equation:

Back 238

CO2 + 2H2O => CH2O + H2O + O2

Front 239

List the basic components of an activated sludge system.

Back 239

A. Aeration tanks
B. Blowers and diffusers or mechanical aerators
C. Clarifiers
D. RAS/WAS pumps

Front 240

The aeration system in the activated sludge provides

Back 240

oxygen to the microorganisms and mixes the contents of the aeration basins

Front 241

Centrifugal:

Back 241

A blower consisting of an impeller fixed on a rotating shaft and enclosed in a casing having an inlet and a discharge connection

Front 242

Positive Displacement:

Back 242

A positive displacement (PD) blower forces air to move by
trapping a fixed amount, then displacing that trapped volume into the discharge pipe.

Front 243

Fine Bubble Diffusers

Back 243

A device through which air is pumped and divided into very small bubbles that are used to introduce and dissolve oxygen into the liquid. Fine bubble diffusers are normally disks or tubes that use membranes or ceramic materials to create the bubbles and gentle mixing action.

Front 244

Coarse Bubble Diffusers

Back 244

A device through which air is pumped and divided into large bubbles that are transferred and dissolved into the liquid.

Front 245

Fine bubble diffusers are normally

Back 245

disks or tubes that use membranes or ceramic materials to create the bubbles and gentle mixing action.

Front 246

Coarse bubble diffusers normally

Back 246

discharge air at a high rate and are installed to induce a spiral or cross roll mixing pattern

Front 247

The most common types of mechanical aerators utilize

Back 247

paddles or discs and spray or turbine mechanisms

Front 248

Cavitation occurs in wastewater systems when

Back 248

the vacuum pressure at any point in the system is lowered to the vapor pressure of the liquid.

Front 249

Cavitation usually occurs

Back 249

in pumps, on impellers, or at restrictions in a flowing liquid

Front 250

Cavitation can make a pump very noisy. This noise has been described as

Back 250

popping sound, clattering, or like marbles rattling around in the pump

Front 251

Calibrating pumps is a way to check on wear. Regular calibration also helps determine actual flow rates and

Back 251

whether any plugging or infiltration is occurring.

Front 252

To calibrate pumps you first must find the

Back 252

drawn down distance, draw down time, refill
distance and refill time for each pump.

Front 253

In the operation and management of a wastewater system there are four major separate budgetary items needed:

Back 253

Operation and Maintenance Budget,
Capital Improvement
Budget, Replacement Fund,
Debt Retirement

Front 254

Operation and Maintenance Budget

Back 254

Sufficient funds must be available to cover the daily operational and maintenance expenses for the wastewater treatment plant and collection system, including salaries, electric bills for running all the equipment, lubricating pumps and drives, and cleaning sewer pipes

Front 255

Capital Improvements Budget or Loan

Back 255

Significant upgrading or improvement projects often require large expenditures of money. Utilities should establish a capital improvements budget to plan for future treatment plant needs. Sometimes it is not possible to save enough money for a project and in those cases there are a variety of funding methods available including grants, loans, and municipal bonds.

Front 256

Replacement Fund

Back 256

Treatment plant equipment, such as pumps, motors, or aeration equipment have projected lifespans and need to be replaced when reaching the end of their design life. A replacement fund, with readily available funds, allows an operator to replace old or worn out equipment during the useful life of the treatment works to maintain the capacity and performance for which the treatment works were designed and constructed.

Front 257

Debt Retirement

Back 257

The large investment a community has to make in constructing and upgrading a wastewater treatment system often requires loans or bonds from a funding agency and/or financial institutions to be obtained and paid back over the terms of the loan.

Front 258

Aeration basins and clarifiers should be emptied on a regular basis to:

Back 258

A. Perform a detailed inspection of the structure, valves, and control gates
B. Clean out grit and settled solids
C. Maintain equipment and piping.

Front 259

List the items to include in a maintenance schedule for final clarifiers

Back 259

Daily observations should be performed such as checking for oil leaks, unusual vibrations or noises, scum collection, weirs, and floating solids. All maintenance and repairs should be documented

Front 260

Measurements needed to calculate the volume of a retangular well are

Back 260

Length, Width, and Depth

Front 261

Primary sludges are

Back 261

the solids that settle out of the raw wastewater in the primary clarifiers

Front 262

The primary sludges are usually

Back 262

fairly coarse with a specific gravity (density) significantly
greater than water, allowing for rapid settling

Front 263

Primary sludges are typicaly

Back 263

60-80% volatile solids (organic) varying depending on the raw wastewater characteristics.

Front 264

Primary sludge is

Back 264

odorous and requires additional treatment prior to ultimate disposal.

Front 265

Secondary sludges are

Back 265

those solids generated as a part of the secondary treatment process and settle out in the secondary clarifiers

Front 266

Secondary sludges are

Back 266

mainly composed of the microorganisms generated in the secondary process (activated sludge or fixed film systems).

Front 267

Excess Secondary sludge amounts

Back 267

must be removed to keep the secondary system in balance.

Front 268

Secondary sludges are

Back 268

more flocculent, with a specific gravity (density) very close to that of water making them more difficult to settle than primary sludges.

Front 269

Secondary sludges are typicaly

Back 269

75 to 80 percent volatile solids (organic) and contain bound water in the cells of the microorganism, making them difficult to dewater or thicken.

Front 270

Secondary sludges with higher the volatile solids (organics) content

Back 270

the more difficult the sludge is to dewater.

Front 271

Both primary and secondary sludges should be

Back 271

as concentrated as possible by proper operation of clarifiers.

Front 272

The purpose of sludge thickening is to

Back 272

further concentrate and thicken solids settled and wasted from treatment plant processes.

Front 273

Sludge is thickened prior to

Back 273

being pumped to the digester or sludge storage.

Front 274

Common sludge thickening unit processes are

Back 274

Gravity Settling Thickener
Dissolved Air Flotation

Front 275

Gravity thickening consists of

Back 275

a circular tank (usually with a conical bottom) that is fitted with collectors or scrapers at the bottom.

Front 276

With a Gravity Settling Thickener

Back 276

The solids settle to the bottom of the tank by gravity, and the scrapers slowly move the settled, thickened solids to a discharge pipe at the bottom of the tank.

Front 277

Dissolved air flotation thickens sludge by

Back 277

adding dissolved air under pressure and then
releasing the air at atmospheric pressure in a flotation tank or basin

Front 278

With a Cissolved Air Flotation

Back 278

The released air forms tiny bubbles which adhere to the suspended matter causing the suspended matter to float to the surface where it is removed by a skimming device.

Front 279

The purpose of sludge treatment, sometimes also referred to as sludge stabilization, is to

Back 279

reduce the pathogens in the sludge and the attraction of vectors (flies, mosquitos, vermin, birds, etc.)

Front 280

Define: Vectors

Back 280

(flies, mosquitos, vermin, birds, etc.)

Front 281

Class B sludges are

Back 281

sludges that can be applied to agricultural lands

Front 282

Adequate pathogen control for a Class B sludge is

Back 282

< 2,000,000 CFU/g or mpn fecal coliforms or by Anerobic Digestion, Air Drying, Composting, Alkaline Stabilization, & Process to Significantly Reduce Pathogens (PSRP)

Front 283

Anaerobic Digestion is

Back 283

treated in the absence of air for a certain amount of time at a specific temperature. The time and temperature shall be between 15 days at 35 °C to 55 °C and 60 days at 20 °C.

Front 284

Air Drying is

Back 284

dried on sand beds or on paved or unpaved basins for a minimum of 3 months. During 2 of the 3 months, the average daily temperature has to be above 0 °C.

Front 285

Composting is

Back 285

using either a within-vessel, static aerated pile, or windrow composting method and the temperature of the sludge raised to 40 °C or higher for 5 days. For 4 hours during the 5 days, the temperature in the compost pile has to exceed 55 °C.

Front 286

Alkaline Stabilization is when

Back 286

Lime is added to sludge to raise the pH to 12 for 2 hours of contact.

Front 287

Process to Significantly Reduce Pathogens (PSRP) Equivalent is

Back 287

treated in a process that is equivalent to a process to significantly reduce pathogens, as approved by the department. Many such processes are proprietary.

Front 288

The purpose of dewatering sludge is to

Back 288

significantly concentrate the solids and reduce the liquid content of the sludge.

Front 289

EPA defines biosolids as a

Back 289

“primarily organic solid product yielded by municipal wastewater treatment processes that can be beneficially recycled” as soil amendments (fertilizer and conditioners).

Front 290

Recycling biosolids through land application is a

Back 290

sustainable management method to reuse nutrients and soil conditioners in place of commercial fertilizers, and avoid disposal in landfills.

Front 291

In activated sludge aeration basins

Back 291

mixed liquor suspended solids is expressed in milligrams per liter (mg/L)

Front 292

As solids are thickened and the concentration gets to 10,000 mg/L or above

Back 292

the solids are then often expressed as a percent. Every 10,000 mg/L is 1%

Front 293

A treatment plant operator has to maintain a daily application log for

Back 293

biosolids land applied each day when land application occurs.

Front 294

A treatment plant operator has to maintain a daily application log for biosolids land applied each day when land application occurs. The following minimum records must be kept

Back 294

A. Approved site used
B. Number of acres of sludge applied on that day
C. Amount of sludge applied that day and amount per acre
D. Amount of nitrogen applied per acre
E. Method of application of the sludge (injection,incorporation, or surface application)

Front 295

When sending samples to a certified lab one must make sure that

Back 295

A. The lab is certified in the test you are submitting your sample.
B. The sample will get there in the appropriate time. For example: Grab samples for pH cannot be sent out due to the holding time requirements and BOD samples must be tested at the certified lab no later than 48 hours after the last composite sample was taken.
C. The paperwork is filled out completely. Certified labs will provide you with a chain of custody form that has all the necessary data needed.
D. The samples are on ice when needed and that the temperature of the samples meet the specific requirements when they reach the certified lab.

Front 296

An automatic sampler takes a series of

Back 296

small samples throughout the day and stores it in a large container.

Front 297

automatic sampler takes a series of small samples throughout the day and

Back 297

At the end of 24 hours, you have a 24 hour composite sample

Front 298

“flow proportional” composite samples are

Back 298

the automatic sampler receives a signal from a flow meter, and takes a sample every so many gallons of flow.

Front 299

The operator wants to take 100 samples per day and wind up with 10 liters of sample.

The flow is 500,000 gpd, and the sample container holds 20 liters.

Back 299

10 liters = 10,000 mL,
so: 10,000 mL ÷ 100 samples = 100 mL/sample
500,000 gpd ÷ 100 samples/day = 5000 gals/sample

Front 300

what is in a Wisconsin Pollutant Discharge Elimination System (WPDES) permit.

Back 300

A. Influent Requirements
B. Surface Water or Land Disposal Requirements
C. Land Application Requirements
D. Schedules of Compliance
E. Standard Requirements
F. Summary of Reports Due

Front 301

(WPDES) permit. Influent Requirements

Back 301

This section of the permit lists the specific influent sampling points and associated monitoring requirements at each point. This provides how much flow and pollutants are coming into the plant.

Front 302

(WPDES) permit. Surface Water or Land Disposal Requirements

Back 302

This section of the permit lists the specific effluent sampling points with associated monitoring requirements and effluent limitations at each point. This provides information on treatment efficiency and the amount and quality of the treated wastewater being discharged from the plant.

Front 303

(WPDES) permit. Land Application Requirements

Back 303

This section of the permit lists the specific sampling points and associated monitoring requirements and limitations at each point. This provides information on the biosolids/sludge that is hauled from the plant and landspread.

Front 304

(WPDES) permit. Schedules of Compliance

Back 304

This section of the permit establishes a time schedule for any reports, upgrading construction requirements or other actions to be met by the permittee.

Front 305

(WPDES) permit. Standard Requirements

Back 305

This section of the permit contains the more general requirements regarding wastewater reporting and monitoring, system operations, surface water discharge, and land application.

Front 306

(WPDES) permit. Summary of Reports Due

Back 306

The end of the permit contains a table that lists and summarizes all the reports that must be submitted and when they are due. Many operators copy this page and post it for ready reference.

Front 307

Discharge Monitoring Report (DMR) is

Back 307

an electronic submittal required by DNR, which includes routine monitoring data from a wastewater facility primarily to determine compliance with permit limits.

Front 308

Discharge Monitoring Report (DMR) reports are submitted electronically

Back 308

to WDNR on a monthly basis, but some facilities submit them quarterly.

Front 309

Monthly Discharge Monitoring Report (DMR).

Back 309

are due on the 15th of the following month.

Front 310

Sanitary Sewer Overflow (SSO)
Whenever there is an overflow occurrence at the treatment works or from the collection system

Back 310

the permittee must notify the Department within 24 hours of initiation of the overflow occurrence by telephoning the wastewater staff in the regional office as soon as reasonably possible (FAX, email or voice mail, if staff are unavailable).
In addition, the permittee shall within 5 days of conclusion of the overflow occurrence report pertinent SSO information in writing on a SSO reporting form provided by the Department.

Front 311

Chemical Storage tanks must

Back 311

have secondary containment that equals the volume of the storage tank.

Front 312

Given the average daily plant flow, calculate the programming of a flow proportional sampler to collect the correct number and volume of samples.

GIVEN:
Average daily flow = 850,000 gallons
24 hour composite volume desired = 5000 mL
Sample container size = 10 liters
Samples/day = 100

FORMULAS
Flow interval (gals/sample) = average daily flow (gpd) ÷ # of samples/day
Volume of sample (mL) = 24 hour composite volume (mL) ÷ # of samples/day

Back 312

Flow interval (gals/sample) = 850,000 gpd ÷ 100 samples/day = 8500 gal/sample

Volume of sample (mL) = 5000 mL ÷ 100 samples/day = 50 mL

Front 313

Given data, determine if an unused circular tank at a treatment plant can be used for 180 day sludge storage. The volume of sludge generated each day is 2500 gallons and the tank is 20 feet deep with a diameter of 50 feet.

GIVEN:
Tank depth = 20 feet
Tank diameter = 50 feet
Gallons of sludge wasted each day = 2500 gallons

FORMULAS
Tank Volume = [3.14 × (radius squared (ft)) × depth (ft)] × 7.48 gal/cu.ft

Back 313

Sludge Volume Needed = 2500 gallons/day × 180 days
= 450,000 gallons

Tank Volume = [3.14 × (radius squared (ft)) × depth (ft)] × 7.48 gal/cu.ft
= [3.14 × (25 ft × 25 ft) × 20 ft] × 7.48 gal/cu.ft
= 293,590 gallons

Since the sludge wasted that needs to be stored over 180 days is 450,000 gallons and the tank is only 293,560 gallons, the tank by itself is too small to be used for 180 days of storage.

Front 314

Given data, during wet weather, determine if a chlorine contact tank is of sufficient volume to meet a 30 minute detention time at peak hourly flow.

GIVEN:
Tank depth = 15 feet
Tank length = 20 feet
Tank width = 15 feet
Peak hourly flow = 35,000 gal/hour
Detention time needed = 30 minutes

FORMULAS
Tank volume (gallons) = [length (ft) × width (ft) × depth (ft)] × 7.48 gal/cu.ft.
Detention time (minutes) = [tank volume (gal) ÷ flow rate (gal/hour)] × 60 minutes/hour

Back 314

Tank volume (gallons) = [20 ft × 15 ft × 15 ft] × 7.48 gal/cu.ft.
= 33,660 gallons

Detention time (minutes) = [33,660 gallons ÷ 35,000 gal/hour] × 60 minutes/hour
= 0.96 hours × 60 minutes/hour
= 57 minutes

YES, the chlorine contact is able to meet the 30 minute detention time during wet weather
peak hourly flow.

Front 315

Given data, calculate the pounds of BOD5 entering the treatment plant each day.

GIVEN:
Influent flow = 0.845 MGD
Influent BOD = 320 mg/L
1 gallon = 8.34 lbs

FORMULA
Influent BOD5 (lbs/day) = influent flow in MGD × influent BOD5 in mg/L × 8.34 lbs/gal

Back 315

= (0.845 MGD) × (320 mg/L) × 8.34 lbs/gal
= 2255 lbs/day

Front 316

Given data, determine the food to microorganism ratio (F/M) in the aeration basin of an activated sludge treatment plant.

In an activated sludge plant, food to microorganism ratio is the amount of food (BOD5 in lbs) relative to the amount of biomass (mixed liquor suspended solids in lbs) in the aeration basin.

GIVEN:
Influent flow (MGD) = 0.125 MGD
Influent BOD5 (mg/L) = 280 mg/L
Aeration basin volume = 0.200 MG
Aeration basin MLSS = 2100 mg/L
1 gallon = 8.34 lbs

FORMULA
F/M Ratio = pounds of incoming BOD5 ÷ pounds of MLSS under aeration
F/M Ratio = [(influent flow in MGD) × (influent BOD5 in mg/L) × 8.34 lbs/gal]
divided by
[(aeration basin volume in MG) × (MLSS in mg/L) × 8.34 lbs/gal]

Back 316

= [(0.125 MGD) × (280 mg/L) × 8.34 lbs/gal] ÷ [(0.2 MG) × (2100 mg/L) × 8.34 lbs/gal]
= 292 lbs BOD5 ÷ 3503 lbs MLSS
= 0.08

Front 317

Given data, calculate the size of an emergency (trash) pump that will be needed to pump to a downstream manhole during a power outage at a lift station wet well to avoid a sewage overflow or basement backup.

GIVEN:
Size of lift station wetwell = 10 ft × 10 ft
Depth of wetwell = 15 ft
Fill time of wet well during storm = 10 minutes
1 cubic foot = 7.48 gallons

FORMULAS
Wetwell volume (gallons) = [length (ft) × width (ft) × depth (ft)] × 7.48 gal/cu.ft
Sewage flow (gpm) = wetwell volume (gal) ÷ fill time (mins)

Back 317

Wetwell volume (gal) = [10 ft × 10 ft × 15 ft] × 7.48 gal/cu.ft
= 1500 cu.ft × 7.48 gal/cu.ft
= 11,220 gallons
Sewage flow (gpm) = 11,200 gallons ÷ 10 minutes
= 1,120 gpm
----> USE AT LEAST A 1500 gpm pump

Front 318

Given data, calculate the pump rate in gallons per minute of this lift station pump.

GIVEN:
Wet well diameter = 7 feet
Drawdown time = 250 seconds
Drawdown distance = 1.33 feet
Refill time = 400 seconds
Refill distance = 1.25 feet
1 cubic foot = 7.48 gallons
60 seconds = 1 minute

FORMULA
Pump rate (gpm) = [volume of drawdown (gal) ÷ time (min)] + [volume of refill (gal) ÷ time
(min)]
Pump rate (gpm) = [(3.14 × radius squared (ft) × drawdown (ft) × 7.48 gal/cu.ft) ÷ (drawdown
time (sec) ÷ 60 sec/min)] + [(3.14 × radius squared (ft) × refill (ft) × 7.48 gal/cu.ft) ÷ (refill
time (sec) ÷ 60 sec/min)]

Back 318

Pump rate (gpm) = [(3.14 × (3.5 ft × 3.5 ft) × 1.33 ft × 7.48 gal/cu.ft) ÷ (250 sec ÷ 60
sec/min)] + [(3.14 × (3.5 ft × 3.5 ft) × 1.25 ft × 7.48 gal/cu.ft) ÷ (400 sec ÷ 60 sec/min)]
= [383 gals ÷ 4.2 mins] + [360 gals ÷ 6.7 mins]
= 91 gpm + 54 gpm
= 145 gpm

Front 319

Given data, calculate detention time for multiple clarifiers operating in parallel.

GIVEN:
Primary clarifiers = 2
Clarifier diameter = 80 feet
Clarifier depth = 12 feet
Average daily flow = 7.2 MGD
1 cubic foot = 7.48 gallons
Note: both clarifiers receive equal flows

FORMULA
Volume (gal) = # of clarifiers × (3.14 × [radius squared (ft)] × height (ft) × 7.48 gal/cu.ft)
Detention time = tank volume (gal) ÷ flow rate (gal/hour)

Back 319

Volume (gal) = 2 clarifiers × (3.14 × [40 ft × 40 ft] × 12 ft) × 7.48 gal/cu.ft
= 901,908 gallons
Detention time = 901,908 gallons ÷ [7,200,000 gpd ÷ 24 hours/day]
= 901,908 gallons ÷ 300,000 gal/hour
= 3 hours
Note: this can also be calculated by using the volume of 1 clarifier and dividing the flow by 2.

Front 320

Given data, calculate the percent of BOD5 being treated and removed.

GIVEN:
Influent flow = 1.2 MGD
Influent BOD5 = 240 mg/L
Effluent flow = 1.2 MGD
Effluent BOD5 = 10 mg/L
1 gallon = 8.34 lbs

FORMULA
BOD5 removed (lbs) = influent BOD5 (lbs) - effluent BOD5 (lbs)
BOD5 removed (lbs) = [(influent flow in MGD) × (influent BOD5 in mg/L) × 8.34 lbs/gal]
minus
[(effluent flow in MGD) × (effluent BOD5 in mg/L) × 8.34 lbs/gal]
Percent (%) removal = [(influent BOD (lbs) - effluent BOD (lbs)) ÷ influent BOD (lbs)] × 100

Back 320

BOD5 removed (lbs) = [(1.2 MGD) × (240 mg/L) × 8.34 lbs/gal] - [(1.2 MGD) × (10 mg/L) ×
8.34 lbs/gal]
= 2400 lbs - 100 lbs
= 2300 lbs BOD5 removed
Percent (%) Removal = [(2400 lbs - 100 lbs) ÷ 2400 lbs] × 100
= (2300 lbs ÷ 2400 lbs) × 100
= 96%