Operation Of Wastewater Treatment Plant Volume 2

Front 1

What is the purpose of the activated sludge process in treating Wastewater?

Back 1

To oxidize and remove soluble or finely divided suspended materials that were not removed but previous treatment.

Front 2

What is a stabilized waste?

Back 2

Waste that has been treated or decomposed to the extent that it 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 3

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

Back 3

To provide oxygen to sustain the living organisms as they oxidize ways to obtain energy for growth the application of air also encourages mixing in the aerator.

Front 4

What happens to the air requirement in the aeration tank when the strength (BOD) of the incoming Wastewater increases?

Back 4

Air requirements increase when the strength (BOD) of the incoming Wastewater increases because more food (waste) encourages biological activity (reproduction and respiration).

Front 5

What factors could cause an unsuitable environment for the activated sludge process in an aeration tank?

Back 5

1. High concentrations of acids bases and other toxic substances.

2. Uneven flows of Wastewater that cause overheating or starvation.

3. Failure to supply enough oxygen.

Front 6

What two different ways may effluent quality requirements be stated by Regulatory Agencies?

Back 6

Terms of percentage removal of waste or allowable quantities of waste that may be discharged.

Front 7

What two major variables affect the way an activated sludge plant is operated?

Back 7

1. Changes in Wastewater characteristics and collections system flows

2. In plant operational variables.

Front 8

What problems can be caused in an activated sludge plant when excessive storm water flows through the process?

Back 8

1. Reducing treatment time of the Wastewater

2. Increasing the amount of grit and salt

3. Increasing the organic loading

4. Causing fluctuations in Wastewater temperature and solids content

Front 9

Besides excessive storm water flows what other variable in the collection system can affect the operation of an activated sludge plant?

Back 9

Maintenance activities and waste discharges.

Front 10

What are the purposes of aeration?

Back 10

Providing dissolved oxygen and mixing of the mixed liquor and Wastewater in the aeration tank.

Front 11

List two methods of supplying oxygen from Air to bacteria in the activated sludge process.

Back 11

Mechanical aeration and diffused aeration.

Front 12

Why are diffusers located near the bottom of the aeration tank?

Back 12

Maximize the contact time of the air bubbles with the mix liquor. Also this location encourages mixing and discourages deposits on the tank bottom.

Front 13

How are the guide vanes positioned that control air output from the centrifugal blowers?

Back 13

Manually by operating Personnel or by plant instrumentation responding to dissolved oxygen levels in the aeration tanks or to plant influent flows.

Front 14

Why are fine bubble diffusers easily clogged?

Back 14

These diffusers are self-sealing from the inside if dirty air is pumped into the diffusers. They may also clog from the outside due to biological growth.

Front 15

What precautions must be taken before attempting to maintain or repair a surface aerator?

Back 15

Shut down the aerator and be sure the main power breaker is opened (shut off), locked out, and properly tagged.

Front 16

What information should be on a lockout tag?

Back 16

The date of the lockout, the reason for the lockout, and the name of the person who locked out the equipment.

Front 17

What precautions should be taken when working with blowers?

Back 17

1. Be sure all Inlet and discharge valves are open before starting.

2. Remove all foreign matter that may enter the blower.

3. All personnel must be clear of blower before starting.

4. Always wear hearing protection when working near an operating blower (make sure the hearing protectors reduce your noise exposure adequately).

5. When shutting down a blower, be sure the main power breaker is opened (shut off) locked out and properly tagged.

6. Allow only qualified and authorized electricians to troubleshoot and repair electrical problems.

Front 18

Why should the operator completely check the equipment and structures before start up?

Back 18

To familiarize the operator with plant equipment and locations of piping and also to be reasonably sure that everything will function properly when the plant is put into service.

Front 19

If your plant does not have a manufacturer's manual, how would you obtain one?

Back 19

A new one may be obtained by writing the manufacturer and giving them the name, size, serial number, and the treatment plant location and contact number if possible.

Front 20

Why is it important to read the manufacturer's manual before starting any piece of equipment?

Back 20

Most manufacturers normally Supply a one year warranty on their equipment. If the equipment is damaged due to improper operation, the warranty becomes void and your community or District must absorb the cost of repairs and replacement. Proper operation prolongs the life of equipment, reduces the cost of repairs and replacement, and helps prevent operators from being injured.

Front 21

Why should proper procedures be followed when starting, operating, and stopping equipment?

Back 21

To prolong the life of the equipment.

Front 22

Why should lines and channels be cleaned before start up?

Back 22

To remove any debris such as rocks, sand, Timber , waste concrete, or other foreign material that will occupy space or damaged equipment. Cleaning also will familiarize the operator with the flow routes.

Front 23

Why should chips and scrapes on aerator control Gates be painted?

Back 23

For the protection of the equipment against rust and corrosion. The cost of equipment is high, and it is part of the operator's responsibility to take as long a life as possible for a plant equipment.

Front 24

What is the purpose of stop nuts on aerator control gate stems?

Back 24

To limit the length of travel. Without a stop nut the gate could fall into the aeration tank if it is open too far or the stem could be bent if an operator attempts to close the gate further than necessary.

Front 25

Why should an effluent Weir be level?

Back 25

To prevent short-circuiting and an uneven distribution of solids in the effluent.

Front 26

What dangers are created if a foam-control spray nozzle sprays water on a rail or walk?

Back 26

It may create a slipping Hazard either from Ice formation in the winter or algal growths in the summer.

Front 27

How is air cleaned before being compressed and sent to the aeration tank?

Back 27

By the use of air filters.

Front 28

How can you determine when the air filters need cleaning?

Back 28

When the difference in pressure recorded by the manometer reaches approximately two to three inches of water column more than than the initial difference it is probably time to clean or change the filters. See the manufacturer's manual for recommended pressure differences.

Front 29

How should the sharp edge of a metering orifice be placed in a pipe?

Back 29

Usually on the same side as orifice information, which is stamped on the orifice plate handle. The sharp edge should be placed so as to be facing the Stream flow with the bevel on the discharge side. If the office is installed backward it will give an incorrect reading.

Front 30

Why must a hoist used to lift the air headers be properly anchored?

Back 30

The Hoist could catapult into the aeration tank and could cause injury to operators and damage to equipment.

Front 31

What precautions should you take when working on the center Y-wall?

Back 31

Wearing of approved flotation devices or fall arrest systems, having help standing by, keeping the area clear and free of slippery materials, providing secure footing, and requiring adequate lighting.

Front 32

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

Back 32

If they are slanted so that one end of the header cross-arm is higher than the other (by as little as half inch) the air will be unevenly released into the aerator. The diffusers on the high side at a low air rates will allow most of the air to pass out of them through the path of least resistance rather than go through the diffusers that are located on the low end of the header and that have only a half inch more water over the top of them. This creates an undesirable flow pattern in the tank.