Operation Of Wastewater Treatment Plants

Front 1

Settling tanks increase the wastewater veocity far above the velocity in a collection sewer. T or F

Back 1

False

Front 2

Pumping skimmed solids to a digester is considered good practice. T or F

Back 2

False

Front 3

Annually, during periods of low flow, each clarifier should be shut dowm for imspection, routine maintenance, and any necessary repairs. T or F

Back 3

True

Front 4

There is a great deal an operators can do in terms of clarifier operation to improve or maintain clarifier performance under toxic conditions. T or F

Back 4

False

Front 5

The operator;s main concern must be the quality of the plant effluent, regardless of percent of wastes removed. T or F

Back 5

True

Front 6

The accumulated sludge on the floor of a clarifier should be removed frequently. T or F

Back 6

True

Front 7

As thick a sludge as possible should be pumped from the clarifier sump with the least amount of water. T or F

Back 7

True

Front 8

As water temperature increases, the settling rate of particles decreases. T or F

Back 8

False

Front 9

As wastewater enters a settling tank, it should be evenly dispersed across the entire section of the tank and should flow at the same velocity in all areas toward the discharge end. T or F

Back 9

True

Front 10

Actual detention time for a clarifier is often greater than the detention time calculated using the formula. T or F

Back 10

False

Front 11

Trickling filter sloughings are generally quite low in BOD. T or F

Back 11

False

Front 12

Secondary clarifier tanks, which follow the activated sludge process are designed to handle small volumes of sludge. T or F

Back 12

False

Front 13

Laboratory tests should be conducted to provide a check on the accuracy of the monitoring instrumentation. T or F

Back 13

True

Front 14

Sufficient gas is produced in combined sedimentation-digestion units to serve as a reliable source of energy for power or for heating. T or F

Back 14

False

Front 15

One method of operating septic tank effluent leaching systems is to apply effluent to half of the system while the other half rests to give the system a chance to recover its percolation capacity. T or F

Back 15

True

Front 16

What is the main difference between primary and secondary clarifiers?

1. Effluent from a primary clarifier is mormally clearer than secondary effluent

2. Primary clarifiers are usually much larger than secondary clarifiers

3. Secondary sludges are usually denser than primary sludges

4. The density of the sludge handled

Back 16

The density of the sludge handled

Front 17

What is the purpose of a rectangular sedimentation basin eflfuent trough (launder)?

1. collects the settled wastewater flowing over the weirs

2. Drags sludge to the deep end of the sump for removal by pumping

3. Ensures equal flow over all weirs

4. Receives the floating material from the scum skimmer for removal

Back 17

Collects the settled wastewater flowing over the weirs

Front 18

What is the purpose of circular clarifier blades and scraper swueegees?

1. Allows the collected scum to flow from the skimmer box to a scum tank or pump

2. Collects the sludge before withdrawal

3. Removes the sludge from the clarifier

4. Scrapes sludge from the bottom of the clarifier to the sump

Back 18

Scrapes sludge from the bottom of the clarifier to the sump

Front 19

During normal operations, which daily operation and maintenance tasks should be performed with regard to clarifier flights?

1. Examine bolts fro looseness, corrosion, and excessive wear on those parts that can be inspected above the waterline

2. Grease all moving equipment according to manufacturer's specifications and check oil levels in motors where appropriate

3. Using water under pressure, wash off accumulations of solid particles, grease, slime, and other material from walkways, handrails, and all other exposed parts of the structure and equipment

4. Write in your pocket notebook any unusual observations and transfer these notes to the plant record sheet

Back 19

Grease all moving equipment according to manufacturer's specifications and check oil levels in motors where appropriate

Front 20

Why should operators perform an annual inspection on each clarifier?

1. To be in compliance with regulatory requirements

2. To help prevent serious problems and failures in the future when harmful consequences can result

3. To maintain essential clarifier records

4. To provide operators with a opportunity to obverve the submerged equipment

Back 20

To help prevent serious problems and failures in the future when harmful consequences can result

Front 21

In most plants. why do the surface loading and detention time vary widely throughout the day?

1. Due to the hourly changes in plant inflow resulting from the activities of the people and industries in the community

2. Due to the inflow and infiltration from stormwater runoff and groundwater fluctuations

3. Due to the scheduled maintenance activities of the sewer maintenance crews

4. Due to the tidal action of sea water

Back 21

Due to the hourly changes in plant inflow resulting from the activities of the people and industries in the community

Front 22

What is the only conclusive method of measuring the efficiency of clarifiers?

1. By continually observing the quality of the effluent

2. By documenting and recording odor complaints

3. By obtaining regulatory agency approval of efficiency

4. By proper analysis of representative samples

Back 22

By continually observing the quality of the effluent

Front 23

What is the purpose of performing calculations of clarifier treatment efficiency?

1. For laboratory QA/QC purposes

2. For process control purposes

3. To fulfill the needs of the plant administration

4. To satisfy the reporting requirements of regulatory agencies

Back 23

For process control purposes

Front 24

Why should clarifier weirs be kept level?

1. To help operators measure the clarifier effuent flow

2. To help operators record the efficiency of the clarifier

3. To help prevent short-circuiting, which reduces the efficiency of the clarifier

4. To help prevent the growth of algae on the weirs

Back 24

To help prevent short-circuiting, which reduced the efficiency of the clarifier

Front 25

Why must fats, oils, hair, and other light material be removed by flotation?

1. To allow for the recovery and recycling of the this valuable resource

2. To prevent the material from settling to the bottom of the tank

3. To protect the aesthetics (appearance) of receiving waters

4. To remove the material as quickly as possible to avoid odor complaints

Back 25

To protect the aesthetics (appearance) of receiving waters

Front 26

If laboratory results indicate a poorly operating clarifier, how can an operator try to identify the problem?

1. By contacting the regulatory

2. By draining the clarifier and inspecting the interior

3. By questioning the O & M staff

4. By using mathematical methods to check the performance of existing facilities against the design values

Back 26

By using mathematical methods to check the performance of existing facilities against the design values

Front 27

During times when the activated sludge process is upset, why must operators be careful that the return sludge rate does not become too high?

1. The high flows can cause the return sludge pumps to overheat

2. The high flows can overflow the tank weirs and walls

3. The resulting turbulance in the tank can release obnoxious odors

4. The resulting turbulence in the tank can upset the sludge blanket

Back 27

The resulting turbulance in the tank can upset the sludge blanket

Front 28

What does a combined sedimentation-digestion unit consist of?

1. A small chlorinator with a chlorine contact basin

2. A small clarifier constructed over a sludge digester

3. A small grit clarifier with grit-washing facilities

4. A small package plant that includes aerobic digestion

Back 28

a small clarifier constructed over a sludge digester

Front 29

When should digested sludge be withdrawn from the digester of a combined sedimentation-digestion unit?

1. When solids start appearing in the supernatant

2. When the pH in the digester becomes too low

3. When the unit can no longer treat the design influent flow

4. When there is a demand for the biosolids

Back 29

When solids start appearing in the supernatant

Front 30

How is the effluent from a septic tank usually disposed of?

1. In cooling towers

2. In evaporation ponds

3. In storm sewers

4. In underground perforated pipes called leach lines

Back 30

in underground perforated pipes called leach lines

Front 31

Which types of sludge handling and sludge disposal systems are used at wastewater treatment plants?

1. Activated sludge systems

2. Burial systems

3. Digestion systems

4. Filter presses

5. Land disposal systems

Back 31

2,3,4,5

Front 32

Which items could cause the clarifier squeegee mechanism to jerk or jump?

1. A nonuniform sludge blanket on the clarifier floor

2. An uneven clarifier floor

3. An uneven water depth within the clarifier

4. Problems with the drive unit

5. Squeegees that have too much drag

Back 32

2, 4, 5

Front 33

Most clarifiers that do not produce an acceptable effluent usually fail due to which problems?

1. Equipment failures

2. excessive hydraulic loadings (shock loads)

3. Operator errors

4. Recordkeeping system

5. Sloppy laboratory

Back 33

1, 2, 3

Front 34

The installation of which items will help operators maintain clarifier performance under abnormal conditions?

1. Chemical feed systems

2. Comminutors

3. Control structures

4. Instrumentation

5. Monitoring devices

Back 34

1, 3, 4, 5

Front 35

Which items are probable causes of floating sludge (bulking) in primary clarifier?

1. Insufficient sludge removal

2. Sludge blanket is too deep

3. Sludge collection mechanism, or flights, are OFF

4. Sludge decomposing in the tank is lifted by gasification

5. Sludge pump runs but discharges are thin or no sludge is pumped

Back 35

1, 2, 3, 4

Front 36

Which items are possible clarifier problems an operator could encounter?

1. Large amounts of floating scum

2. Loss of solids over the effluent weirs

3. pH is low and there are odors

4. Removal efficiencies are low

5. Sludge blanket is deep but the pumped sludge is thin

Back 36

1, 2, 3, 4, 5

Front 37

Which items should an operator check if floating chunks of sludge are observed on the surface of a clarifier?

1. Collector mechanism

2. Pipes and sludge sump

3. Plant influent

4. Quality of the supernatant return from the digester

5. Sludge pump

Back 37

1, 2, 3, 4, 5

Front 38

Which items are general maintenance hints that will help keep clarifiers operating properly?

1. Always lubricate equipment at the intervals recommended by the manufacturer

2. Clean all equipment and structures regularly

3. Inspect and correct (if possible) all peculiar noises, leaks, pressure and vacuum gauge irregularities, belts, electric systems, and safety devices

4. Keep the weirs level

5. Maintain a record and file system for future reference

Back 38

1, 2, 3, 4, 5

Front 39

The sedimentation and flotation units commonly used to treat wastewater include which items?

1. Activated sludge units

2. Combined sedimentation-digestion units

3. Imhoff tanks

4. Primary clarifiers

5. Secondary clarifiers

Back 39

2, 3, 4, 5

Front 40

Short-circuiting in clarifiers can be prevented by which means?

1. Adequate preventive maintenance

2. Proper design of inlet channels

3. Use of baffles

4. Use of port openings

5. Use of weir plates

Back 40

2, 3, 4, 5

Front 41

Detention time for a clarifier can be calculated by the use of which known factors?

1. Depth of the sludge blanket

2. Hydraulic capacity of the influent pump

3. Quantity of flow per day

4. Tank dimensions or volume

5. Weight of the water in the clarifier

Back 41

3, 4

Front 42

Why should operators review the plans and specifications for a wastewater treatment plant?

1. To become familiar with a proposed plant

2. To check the calculations of the construction costs

3. To learn what will be constructed

4. To look carefully for potential safety hazards

5. To offer suggestions on how the plant can designed for easier and more effective operation and maintenance

Back 42

1, 3, 5

Front 43

When reviewing the plans and specifications for a proposed wastewater treatment plant, which safety items should an operator check?

1. Adequate guards must be placed over chain drives, belts, and other moving parts

2. Adequate lighting must be provided on the clarifier

3. Carwalks and bridges must have floor plates or gates firmly secured and equipped with toeboards and non skids surfaces

4. Do not allow any pipes or conduits to cross on top of catwalks or bridges

5. Safety hooks, poles, or floats should be stationed at strategic locations

Back 43

1, 2, 3, 4

Front 44

Under normal operating conditions for combined sedimentation-digestion units, which tasks should be performed daily?

1. Hose down the baffles, weirs, scum, trough, and scum pit to remove any grease, scum, or other floating debris

2. Look and listen for any thing unusual

3. Measure the pH in the digester

4. Observe the flow through the facility and the operation of the equipment

5. Remove debris and solids from the bar screen and properly dispose of them by burial

Back 44

1, 2, 3, 4, 5

Front 45

Under which circumstances are abnormal operating conditions likely to occur for a combined sedimentation-digestion unit?

1. Inflows are higher than design flows due to stormwater inflow and infiltration

2. Inflows follow a diurnal pattern

3. Residents discharging to the collection system are using specified procedures

4. Solids loadings are high die to seasonal or industrial discharges

5. Toxic substances or high or low pH liquids are released into the collection system

Back 45

1, 4, 5

Front 46

Upon which items should the operator focus during an inspection of a combined sedimentation-digestion unit?

1. BOD level

2. Corrosion damage

3. Cracks and leaks

4. Unpainted surfaces

5. Worn parts

Back 46

2, 3, 4, 5