Math

Question 1

How many pounds of solids are under aeration in an aeration tank with a capacity of . 5 MG when MLSSis 3700mg/L?

Answer 1

15429 pounds.

Question 2

Calculate the perent redution in volatile matter during digestion if the raw sludge was 77% volatile matter and the digested sludge is 29% volatile matter

Answer 2

88%

Question 3

a circular clarifier with a radius of 30 feet and a side wall depth of 10 feet, receiving a flow of 2 MGD, has a detention time equal to…

Answer 3

2.5 hours

Question 4

What should be the approximate chlorine feed rate for a flow of 2 MGD and a chlorine dose of 12 mg/L

Answer 4

200 lbs/24hr

Question 5

a rectangular sedimentation tank 10 feet deep, 25 feet wide and 100 feet long handles a flow of 2.5 MGD. The detention time is:

Answer 5

1.8 hours

Question 6

Wastewater is running full in a 6 inch gravity pipe. What is the change in velocity when the pipe size is increased to 12 inches, iftheflow remains constant?

Answer 6

1/4 as much

Question 7

12,000 gallons o raw sludge is pumped to an anaerobic digester. Lab test show %TS = 5.5% and
%VS = 74.8. Calculate the pounds of VS pumped to the digester.

Answer 7

4,120 lbs

Question 8

A small town of 10,000 people is served by a 30 acre facultative pond. Flow to the pond is a 0.8 MGD witha BOD of 126 mg/L. The pond is operated at depth of 5 ft. Calculate the organic loading to the pond.

Answer 8

56 lbs of BOD/acre/day

Question 9

What is the volatile acid/alkalinity relationship in a digester if the alkalinity is 1670 mg/L and the volatile acids are 100 mg/L.

Answer 9

0.06

Question 10

A digester contains 1500 pounds of volatile matter under digestion. If 0.10 pounds of new volatile solids can be added per day per pound of volatile matter under digestion, how many pounds of sludge solids can be added per day with a volatile conent of 68%.

Answer 10

220 pounds per day

Question 11

8,500 gallons of sludge with a sludge solids concentration of 2% is thickened to a sludge solids concentration of 5%. What is the reduction in volume of sludge?

Answer 11

5,100 gallons

Question 12

A tank has a volume of 200,000 GPD, what is the detention time?

Answer 12

240 hours

Question 13

Determine the pond organic loading in pounds of BOD per acre per day if the inlow is 3.6 MGD with a BOD of 120 mg/L and the pond area is 42 acres.

Answer 13

86 lbs BOD/day/acre

Question 14

Lab test indicate a chlorine dose o 17 mg/L is necessary for adequate plant effluent disinfection. For a low o 2.2 MGD what should be the feed setting on the chlorinator?

Answer 14

312 lbs./24 hr.

Question 15

With a raw sewage BOD of 200 mg/L, and a primary effluent BOD of 80 mg/L the percent reduction is

Answer 15

60%

Question 16

A rectangular sedimentation tank 10 feet deep, 25 feet wide and 200 feet long handles a flow of 5.0 MGD. The surface loading rate is approximately

Answer 16

1,000 GPD/sq. ft.

Question 17

A stick travels 64 feet in 43 seconds in a grit channel. Estimate the flow velocity in the grit channel?

Answer 17

1.5 ft/sec

Question 18

What is the mean?
Week M T W TH F
1 6.0 6.5 5.4 7.2 6.8
2 7.2 8.2 8.0 7.6 9.1

Answer 18

7.2

Question 19

What is the range?
Week M T W TH F
1 6.0 6.9 5.4 7.5 5.8
2 7.2 8.2 9.0 7.6 9.1

Answer 19

5.4-9.1

Question 20

What is the median?
Week M T W TH F
1 6.0 6.8 5.4 7.3 6.8
2 7.2 7.2 8.7 7.6 8.1

Answer 20

7.2

Question 21

What is the organis loading rate on a 6 acre pond if the influent flow rate is 0.06 MGD with a BOD of 205 mg/L?

Answer 21

17 lbs/acre/day

Question 22

An aerobic digester with a volume of 120,000 gallons receives 20,000 GPd of thickened sludge. The sludge is 3.0% sludge solids and 65% volatile matter. What is the volatile sludge solids loading?

Answer 22

.03 lbs VSS/day/gal or .21 lbs VSS/day/cu ft.

Question 23

A flow of 2,100 GPM is approximately the same as

Answer 23

3.00 MGD

Question 24

Does this data indicate a trend?
Week M T W TH F
1 6.0 6.5 5.4 7.4 6.8
2 7.2 8.2 8.7 7.6 9.1

Answer 24

yes

Question 25

At a 2.5 MGD wastewater treatment plant the primary clarifier has a dterntion time of 2 hours. How many gallons does this clarifier hold?

Answer 25

250,000 gallons

Question 26

A treatment plant receives a flow of 7.0 MGD. If the clarifier is 200 feet long, 30 feet wide, and 15 feet deep. What is the surface loading rate?

Answer 26

1170 gal/sq ft/day

Question 27

Estimate the pounds of solids in a 175,000- gallon aeration tank if the suspended solids concentration is 4,600 mg/L?

Answer 27

6,700

Question 28

Primary sludge containing 5% solids is pumped to a digester continuosly at a rate of 25 gpm. How many pounds of volatile solids are added to the digester each day if the volatile solids content is 73% of the total solids.?

Answer 28

10,960 lbs/day

Question 29

Approximately how far down should the level in a wet well be lowered in six minutes by a pump iwth a rated capacity of 200 GPM? the wet well is four feet wide and six feet long.

Answer 29

6.7 feet

Question 30

A trickling filter 80 feet in diameter and five feet deep receives a flow of 2.8 MGD with a BOD of 55 mg/L. The hydraulic loading on the trickling filter is approximately

Answer 30

557 GPD/sq. ft.

Question 31

A trickling filter 40 feet in radius and five feet deep receives aflow of 1.4 MGD with a BODof 110 mg/L. The organic loading on the trickling filter is approximately

Answer 31

51 lbs BOD/day/1,000 cu ft.

Question 32

A tank 40 feet wide, 100 feet long and 10 feet deep is filled in 7.0 hours. How many gallons per minute are entering the tank?

Answer 32

712 GPM