Operation Of Wastewater Treatment Plants

Front 1

The Ratio of food to organisms is a primary control in the activated sludge process.

Back 1

True

Front 2

The treatment plant operator has significant control over the make-up or amount of influent coming into the treatment plant.

Back 2

False

Front 3

Extended aeration produces as much waste sludge as other activated sludge processes.

Back 3

True

Front 4

Mechanical aerators in the aeration tank tend to be higher in installation and maintenance costs than diffused air systems.

Back 4

False

Front 5

When starting a new activated sludge package plant, operators should try to build up the solids or mixed liquor suspended solids (MLSS) as quickly as possible during startup.

Back 5

True

Front 6

Some sludge must be wasted routinely from a package activated sludge plant to achieve optimum plant performance.

Back 6

True

Front 7

Operators should practice safety, avoid hazardous conditions, and use safe procedures.

Back 7

True

Front 8

Oxidation ditches always have a primary settling tank and grit removal system.

Back 8

False

Front 9

Lost time, injury, and even death are the results of not being concerned with applying the rules of safety to all activities involved in operating and maintaining a plant.

Back 9

True

Front 10

Influent flows and waste characteristics are subject to limited control by the operator.

Back 10

True

Front 11

The shallower the oxidation ditch rotors sit in the water, the greater the transfer of oxygen from the air to the water (greater DO).

Back 11

False

Front 12

Odor at an oxidation ditch plant may be a sign of poor housekeeping.

Back 12

True

Front 13

To prevent injury to personnel, shut down the oxidation ditch rotor assembly whenever any maintenance function is performed.

Back 13

True

Front 14

Oxidation ditch plans and specifications must provide standby or auxiliary power to operate critical equipment.

Back 14

True

Front 15

What is stabilized waste?

Back 15

A waste that has been treated or decomposed to the extent that, if discharged or released, its rate and state of decomposition would be such that the waste would not cause a nuisance or odors in the receiving water.

Front 16

What is the purpose of the activated sludge process?

Back 16

The oxidation and removal of soluble or finely divided suspended materials that were not removed by previous treatment.

Front 17

What is agglomeration?

Back 17

The growing or coming together of small scattered particles into larger flocs or particles, which settle rapidly.

Front 18

Why should an operator determine activated sludge solids concentrations in the aerator and the secondary clarifier?

Back 18

For Process control purposes.

Front 19

How can operators build up the solids or mixed liquor suspended solids (MLSS) as quickly as possible during the start-up of an activated sludge plant?

Back 19

By not wasting sludge until the desired level of MLSS is achieved.

Front 20

Whenever an aeration tank must be drained, why should the operator try to determine the groundwater level?

Back 20

Because a high groundwater level can float a tank and cause considerable damage to structures and pipes.

Front 21

During the start-up of an oxidation ditch plant, what is essential for the plant to succeed in reducing the quantities of polluting materials in the raw wastewater?

Back 21

Development of a proper microbial floc.

Front 22

During oxidation ditch plant start-up, what does a dark gray color of the developing mixed liquor suspended solids (MLSS) indicate?

Back 22

A lack of bacterial buildup.

Front 23

In the oxidation ditch process, how is control of rotor oxygenation achieved?

Back 23

By adjusting the ditch outlet level control weir.

Front 24

Which factor determines the flow velocity in an oxidation ditch?

Back 24

Sufficient to prevent the deposition of floc.

Front 25

Why is it usually necessary to vary the amount of mixed liquor suspended solids (MLSS) in the ditch as seasons change?

Back 25

Because the microorganisms are more active in the summer at high temperatures.

Front 26

Oxidation ditch drive and gear assemblies should be elevated out of the water and have which other provision?

Back 26

Safe and easy access for maintenance.

Front 27

Insufficient oxygen in the aeration tank of an activated sludge process will have which effects?

Back 27

Favor the production of foul-smelling intermediate products of decomposition and incomplete reactions.

Front 28

For the activated sludge process to work properly, the operator must control which factors?

Back 28

Dissolved oxygen in the aeration tanks.

Front 29

Effluent quality requirements may be stated by regulatory agencies in terms of which factors?

Back 29

Allowable quantities of wastes that may be discharged.

Percentage removal of wastes.

Front 30

How can an operator determine if not enough air is being supplied to the aerator?

Back 30

Aeration compartment has a rotten egg odor.

Front 31

If odors from waste activated sludge drying beds are a problem, which items are possible solutions?

Back 31

Arrange for disposal of the excess activated sludge at a nearby treatment plant.

Have the excess or waste activated sludge removed by a septic tank pumper and disposed of in an approved sanitary landfill.

Waste the excess activated sludge into an aerated holding tank.

Front 32

When troubleshooting the activated sludge process, which problems should the operator look for?

Back 32

Foaming/ frothing

Odors

Solids in the plant effluent

Front 33

Which items should an operator consider in the day to day operation of a package activated sludge plant?

Back 33

Adjusting the oxygen level accordingly, if an increase or decrease in organisma occurs, to maintain proper solids settling and procustion of a clear final effluent. Avoiding injuries by avoiding hazards and following safe procedures. Ensuring that the return sludge flow rate i such that it allows for a high concentration of solids, which will reduce the amount of water returned to the aerator. Making a final and detailed check of the equipment for proper operation before leaving the plant for the day. Referring to a troubleshooting guide or checklist when a problem develops in the activated sludge process.

Front 34

What are the purposes of the oxidation ditch rotor?

Back 34

To cause surface aeration, which transfers oxygen from the air to the water for respiration by the microorganisms.

To keep the contents of the ditch mixed and moving.

Front 35

What are the primary objectives of oxidation ditch startup?

Back 35

To develop a proper microbial floc (activated sludge) in the oxidation ditch.

To make certain that all mechanical equipment is operating properly.

Front 36

During the period of start up of an oxidation ditch plant, wastewater testing procedures should be initiated for which influent items?

Back 36

BOD

COD

Front 37

Over oxygenation of an oxidation ditch is a problem for which reasons?

Back 37

Excessive DO levels can cause a pinpoint floc to form that does not settle.

Floc can be lost over the weir in the settling tank.

Wastes power.

Front 38

The clarity of the supernatant, usually visible a few feet upstream from the oxidation ditch rotor, will depend on which factors?

Back 38

Concentration of MLSS

Ditch velocity

Settling characteristics of the activated sludge solids.

Front 39

Daily oxidation plant cleanup usually involves which tasks?

Back 39

Removing and burying debris that may have accumulated on the bar screen.

Removing grease and scum from the surface of the clarifier.

Washing or brushing down the clarifier weirs and walls.

Washing or brushing down the ditch.

Front 40

Which items should operators check when reviewing plans and specifications for oxidation ditch plants?

Back 40

All drive and gear assemblies should be elevated out of the water.

Standby or auxiliary power must be provided to operate critical equipment.

The ditch should be constructed with some type of lining.

Walkways with railings must be provided across the aeration channel to provide access to the rotor for maintenance.

Water level in the aeration channel should be controlled by an adjustable weir.