Pa Wastewater Module 15 (The Activated Sludge Process Part 1)

Front 1

What purpose does the activated sludge process serve within wastewater treatment?

Back 1

To oxidize and remove soluble or finely divided suspended materials that were not removed by previous treatment (preliminary and primary).

Front 2

When the biochemical oxygen demand (BOD) of incoming wastewater increases, what happens to the air requirement in the aeration tank?

Back 2

Air requirements increase––more food (BOD) encourages biological activity, which in turn requires more air (oxygen).

Front 3

Why is air added to the aeration tank in the activated sludge process?

Back 3

Air is added to the aeration tank in the activated sludge process to provide oxygen to sustain the living organisms as they oxidize the wastes to obtain energy for growth. The application of air also provides mixing to ensure that the oxygen and food (BOD) are distributed to all the organisms.

Front 4

What does the volatile content of the mixed liquor suspended solids represent?

Back 4

The volatile content of the mixed liquor suspended solids represents the amount of microorganisms in the activated sludge process.

Front 5

What influences the amount of air required in an aeration tank?

Back 5

The amount of food (BOD) in the wastewater and type of treatment are the principal influences on the amount of air required in the aeration tank.

Front 6

Aerobic organisms grow relatively quickly, efficiently oxidize waste, produce little or no odor, but require a proper amount of dissolved oxygen to function properly.

a. True b. False

Back 6

True

Front 7

The conventional activated sludge process produces a high quality of effluent and the process has some ability to absorb _____loads

Back 7

The conventional activated sludge process produces a high quality of effluent and the process has some ability to absorb shock loads

Front 8

As the water temperature drops, water will be able to dissolve:

a. more oxygen b. less oxygen

Back 8

a. more oxygen

Front 9

Diffused aeration systems are the most common. Can anyone tell me why this might be true?

Back 9

More versatile, mobility, cost effective––can make repairs which do not require shutting down the whole tank, can adjust airflow to be more efficient, etc.

Front 10

Slips, trips, and falls

Back 10

 Make sure the walking surface is clean and dry (remove slime and brush away standing water).

 Keep handrails in place, if possible.

 Wear fall arrest device.

Front 11

Drowning

Back 11

 Wear flotation device.

 Shut off aeration to the header being serviced.

Front 12

Overhead falling hazards

Back 12

 Wear hard hats.

 Ensure lifting devices are securely attached.

 Ensure lifting devices are functioning properly.

Front 13

Pressurized line

Back 13

 Relieve the line pressure prior to any work.

 Wear protective eyewear.

Front 14

What are the purposes of aeration?

Back 14

To dissolve oxygen into the wastewater and, to mix the mixed liquor suspended solids with the incoming wastewater. Both of these functions are necessary to ensure the survival of the microorganisms that actually remove the contaminants from the wastewater.

Front 15

What is the difference between mechanical and diffused aeration?

Back 15

Mechanical is done by contacting atmospheric oxygen with the wastewater, either by drawing air into the water or by splashing water into the air. Diffused aeration is done by oxygen or air being “blown” under pressure into the depths of the wastewater through a diffuser.

Front 16

What are the precautions that must be taken before one attempts to maintain or repair a surface aerator?

Back 16

Wear the proper clothing floatation – fall arrest... Turn off machinery. Turn off electricity (tag out/lock out) Wait for motion to STOP.

Front 17

What are some of the hazards that could be found when working on air headers?

Back 17

Because of the location of air headers, slips, trips, and falls are potential hazards. Also, if the work involves lifting, such as with a hoist, care must be taken to ensure that the hoist cable is properly connected; that personnel do not work beneath the hoist or the load; that the hoist is in good working order; and that the load if lifted properly. Finally, if the air line is to be opened, pressurized air, carrying dust or small particles, could be released at a high rate of speed unless the pressure is released first under controlled conditions.

Front 18

If your waste treatment plant were missing a particular manufacturer’s manual, how would you go about obtaining one?

Back 18

Usually the contract specifications require that several copies of manufacturers’ manuals be provided. If they are lost, call or write to the manufacturer or contact the manufacturer’s representative and request another copy of the manual. If the manufacturer’s representative does not have the necessary equipment information, you will need to provide it. Be prepared to provide the equipment serial number, which should have all the necessary information. As additional verification, provide the equipment model number and size, and a purchase contract number if available.

Front 19

Why should an effluent weir be level?

Back 19

An effluent weir should be level to prevent short-circuiting of effluent, to maintain the intended overflow rate, and to minimize solids carry-over, which could occur if high velocity flow patterns are created by the uneven weir setting.

Front 20

As a review, how is air cleaned before it is compressed and sent to the aeration tank?

Back 20

Air filters are used to clean the air.

Front 21

Blowers should be started prior to admitting primary effluent to the aeration tank. Why?

Back 21

Blowers should be started and air should be flowing to the diffusers before primary effluent is admitted to the aeration tank to prevent the diffusers from clogging. Without the air discharging through the diffusers, solids would settle on and stick to the diffusers, but with the air discharging that is less likely.

Front 22

Why must the horizontal pipes containing the air diffusers all be at the same elevation (level)?

Back 22

If the diffusers are not all at the same elevation, the higher diffusers will receive too much air and the lower diffusers will not receive enough (or any) air. This is because the higher diffusers would have less water pressure on them so there would be less resistance to flow. Uneven air distribution would make oxygen transfer less efficient and disrupt the normal mixing pattern in the aeration tank.

Front 23

Why should an operator completely check the equipment and structures before startup?

Back 23

The main reasons to check equipment and structures prior to startup are to: a) become familiar with the equipment, b) learn how it works, c) learn where all the controls are located, d) make sure it is installed properly, and e) have confidence that it should function properly when started up.

Front 24

The _______manual, if available, should contain a wealth of information concerning how to run the plant.

Back 24

The Operations and Maintenance (O&M) manual, if available, should contain a wealth of information concerning how to run the plant.

Front 25

_______plans will summarize the as-constructed information about the plant.

Back 25

Record plans will summarize the as-constructed information about the plant.

Front 26

Out of level weirs can cause an imbalance of flows in the plant and potentially cause problems with the plant effluent.

a. True b.False

Back 26

a. True