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CLASS II REVIEW QUESTIONS

Please show all calculations and circle your math answers. This review sheet contains three (3) times the number of math problems found on an examination. The multiple choice questions are the same as the 1982 revision. The following questions are multiple choice with one correct answer. Circle the letter appearing before the correct answer. 1. A discharge permit application must be submitted 190 days in advance of the present permits

expiration date. No discharge permit is good for longer than:

a. 2 years b. 3 years c. 4 years d. 5 years e. 10 years

2. Nitrogen and phosphorous are biologically significant in waste water because:

a. Nitrogen is reduced to pure nitrogen gas when phosphorous is present as a catalyst and this leads to nitrogen super saturation and rapid fish kills.

b. Nitrogen in the form of nitrates will reduce sodium thiosulfate and thus cause low results in the D.O. test while phosphates will oxidize the iodine to iodide and cause high results.

c. Nitrogen and phosphorous are essential nutrients that can enable aquatic plant growth to become troublesome.

d. Nitrogen pentaphosphate is toxic to the organisms that metabolize. 3. Which of the following units would both logically be found at the same sewage works?

a. Rotary distributors and surface aerators. b. Extended aeration and step aeration c. Anaerobic digesters and primary clarifiers d. Contact stabilization and stabilization ponds e. Primary clarifiers and anaerobic lagoons.

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4. Which of the following would concern you most if found to be at a concentration of 5 mg/l in your raw waste water?

a. Calcium b. Copper c. Sulfates d. Sodium e. Phosphates

5. A primary clarifier does not have adequate detention time. Which of the following would

result?

a. Decreased organic leading on secondary unit b. Overloading of collector or flight drive motor c. Increased solids pumped to digester d. Low BOD removal e. Reduced suspended solids in aeration tank.

6. One change can reduce the fuel consumption for digester heating, increase digester detention

or displacement time and reduce the volume of anaerobic supernatant to be returned to the head works of a treatment plant. That one change would be:

a. Build a bigger digester b. Install a counter-current hear exchanger c. Pump primary sludge more frequently d. Install a sludge thickener e. Double the insulation on the digester roof

7. Your city has just repealed an ordinance that prohibited home garbage grinders, you might

expect:

a. Less raw sludge production b. A decrease in BOD and SS because of the additional garbage grinder flushing water c. Less eggshells per million gallons d. More organic loading e. Less treatment problems

8. What is a backflow preventer?

a. A device to control water hammer in pressure pipes b. An automatic flushing device for instrument purge lines c. A device to prevent backsiphonage d. A device to insure uni-directional flow in metering runs e. None of the above

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9. The advantage in the use of coliform organisms as an indicator lies in the following fact:

a. They are found everywhere and they grow in common bacterial media b. They are found everywhere and are readily killed by chlorine c. They are predominant bacteria associated with intestinal discharges and grow on

nutrient agar forming characteristic colonies 10. The term AMPN@ is used in reference to:

a. The mass of phosphorus and nitrogen per unit of carbon b. The number of coliforms per unit volume of sample that is most likely to have

caused the observed results in a multiple tube test c. The number of fecal stetococci per unit volume of sample that is most likely to have

caused the observed results in the multiple tube test d. The result of membrane filter test e. The standard plate count result

11. How should the pH electrode be stored when not in use:

a. In a strong acid solution b. In a strong caustic solution c. In a safe place in a drawer d. In distilled water e. In a detergent

12. In the normal Winkler test:

a. A snow white precipitate forms in direct proportion to the nitrate concentration b. A brownish flocculant precipitate is evidence that D.O. is absent c. An endpoint is reached when a dark blue color changes to black d. The muffle furnace must be in excess of 500° before incubation e. A snow white precipitate forms if D.O. is absent

13. A pan test should be done monthly on a filter to:

a. Check oil quality in the distributor bearing b. Check sewage distribution on filter c. To check flow rates through the media d. All the above e. None of the above

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14. If a trickling filter has been operating with a hydraulic loading (including some recirculation of 10 to 12 MGAD and organic loading of about 80 pounds of BOD per 1,000 cu. ft./day the treatment efficiency will usually increase if the recirculation is increased. This might be attributed to:

a. The increased recirculation wears down the soluable BOD to finer particles b. The increased flow more completely wets and contacts all of the slime surfaces in the

filter so the food to effective microorganism ration is less as in an activated sludge process

c. The grazing population of warm and other organisms in the filter is flushed out before they consumer the slime bacteria

d. The increased flow more completely fills the under drains so cold updrafts are eliminated

e. The statement is just poppycock put out by power companies to get us to use more electricity to run pumps

15. A MLSS or 30 minute settleability test sample should be collected:

a. At the primary clarifer effluent b. In the return sludge line c. Where the return sludge mixes with the aeration basin contents d. At the aeration basin influent e. At the aeration basin outlet

16. Trickling filters usually consist of a bed of stone which performs its function in sewage by:

a. Mechanical filtration of organic solids b. Mechanical filtration of inorganic solids c. Provides aeration d. Supports a growth of organisms which feed upon the sewage and reduce BOD e. None of the above

17. What is the trickling filter hydraulic loading if the influent flow is 3 mgd and the

recirculation rate is 4:1?

a. 3 mgd b. 6 mgd c. 9 mgd d. 12 mgd e. 15 mgd f. None of the above

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18. The term Aponding@ refers to:

a. The process of discharging sewage treatment plant by-pass flows to temporary storage lagoons

b. The collection of floating oil on a primary clarifier with a floating barrier to facilitate manual skimming

c. The formation of standing pools on top of trickling filters when severe plugging occurs

d. The intentional closure of trickling filter outlet to fill the filter voids for a period to control filter files

e. The removal of mercury in rotary seals to skim off grease and oil contamination before the mercury is placed in the seal

19. If you must waste sludge from an activated sludge plant the maximum rate is

a. 20% per day b. 40% per day c. 60% per day d. 75% per day e. 100% per day

20. A consulting engineer has recommended addition of a roughing filter and intermediate

clarifier between your primary clarifier and aeration basin to better handle increasing industrial loads. This addition would:

a. Be the best form of flow equalization available b. Remove most of the fixed dissolved solids c. Reduce drastically the fine dissolved matter d. Cost a lot and do nothing e. Reduce the organic load on the aeration basin

21. Excess white foam in an aeration basin can be corrected by

a. Decreasing the aeration rate b. Decreasing detention time c. Increasing the MLSS d. Decreasing the MLSS e. Increasing aeration rate

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22. The principal advantage of sludge reaeration in a separate tank is:

a. Longer detention time b. Increases sludge stability c. Increases capacity to handle shock loads d. All the above e. A and B f. B and C

23. Which range is generally best for SVI?

a. 10 - 15 b. 80 - 120 c. 120 - 210 d. 200 - 300 e. Over 300

24. If the return sludge pump does not function the effect on other unit processes will be to:

a. Turn the aeration basin influent dark b. Increase chlorine residual c. Increase effluent suspended solids d. All the above e. None of the above.

25. A rapid and significant increase in filamentous organisms in the mixed liquor may be

expected to:

a. Result in a far better effluent because of the great amount of surface area for absorption

b. Plug up the return sludge pumps because the filaments hang upon valves and gaskets in the sludge line

c. Lead to much denser return sludge because the filaments would tend to strain the dispersed cells of ordinary organisms out of the effluent

d. Cause bulking of the sludge solids to the point that some solids might be swept out along with an otherwise clear liquid phase and result in turbid, poor quality effluent

e. Lead to a much lower F/M ratio because the filaments are so totally insoluble. 26. During severe cold weather operation of an activated sludge plant biological activity and

clarifier sludge settling is reduced. White of the following might help?

a. Increase the MLSS b. Decrease the MLSS c. Increase the D.O. d. Decrease the D.O. e. Add ammonia

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27. A good quality of activated sludge is shown by:

a. Black color and very small particle size b. Finely dispersed milky white particles c. A chocolate brown MLSS that does not settle well in the jar test d. A sludge that settles in one minute in the jar test e. A chocolate color which settles out in 20-30 minutes with a D.O. of 2.0

28. Which set would be most relevant in activated sludge process control?

a. influent SS, MLSS, grit volatility b. MLSS, RAS, cl2 residual, and SS volatility c. influent SS, MLVSS, RAS and MLSS D.O. d. D.O., effluent SS, MLVSSs, and cl2 residual e. influent pH, effluent D.O. and fecal coli and MLVSS

29. Which of the following pairs of actions will help control anaerobic digester operation?

a. regulate CO2 and CH4 b. regulate temperature and biological activity c. regulate volatile acids and CH4 d. regulate temperature and raw sludge feed

30. The progress of anaerobic sludge digestion can be determined by:

a. percent volatile matter in the sludge b. frequent pH and volatile acids determinations c. the volume and composition of gases produced d. all of the above e. a and b only

31. When feeding an anaerobic digester, the operator can control within certain limits:

a. Amount of air available for stabilization b. Solids concentration c. Frequency of feeding d. Organic concentration e. B and d f. B and c

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32. The earliest indication of biological upset or process trouble in heated anaerobic digester would usually be:

a. A significant decrease in pH. b. An increase in the volatile solids percentage in digested sludge c. An increase in alkalinity and a decrease in volatile acids d. An increase in volatile acids without a corresponding increase in alkalinity e. An increase in volatile acids and alkalinity.

33. What is the purpose of heating and mixing a primary anaerobic digester?

a. To prevent grit from settling b. To eliminate all oxygen c. To increase the reaction rate d. To keep methane in suspension

34. A gas meter in the gas line from the digester is most helpful in:

a. Determining whether or not the pressure relief mechanism is functioning properly b. Determining the quantity of gas that should be wasted c. Preventing the gas from exploding d. Measuring the amount of gas produced per day e. Determining how much gas it utilized by the autoclave.

35. What should be done if you anaerobic digester starts to go sour?

a. Release methane and aerate digester b. Add lime or sodium bicarbonate and reduce raw sludge feed c. Add lime and increase raw sludge feed d. Add CO2 to reduce pH e. Drain the tank

36. What might correct air entrainment in a centrifugal pump?

a. Installing a wet well baffle b. Change the wet well influent point c. Increase pump suction submergence d. A and b e. A, b, and c

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37. In regard to operation to centrifugal pumps, which of the following is recommended?

a. Operate at full speed, if variable speed drive is available b. Reduce flow by partially closing valves c. Maintain a positive head on the suction side of the pump d. Don’t install petcocks to exhaust air e. Keep the water pressure to stuffing boxes lower than the pump discharge pressure

38. Before installing new packing, the old packing should be:

a. Realigned b. Lubricated c. Removed d. Sealed evenly at 50 foot pounds e. None of the above

39. What can be a problem with a belt filter press?

a. Washing out b. Polymer overdosing c. Blinding d. All of the above

40. What can be used to evaluate the efficiency of a belt filter press?

a. Vacuum required in inches of mercury b. % volatile solids in cake c. Sludge feed rate in gpd d. Filter yield in lbs/hr/sq ft e. Gph of filtrate removal.

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1. Sample = 50 ml Crucible weight = 21.6329 grams Crucible and dry solids weight = 21.6531 grams Crucible and ash = 21.6380 grams Compute weight percent that was volatile 2. A stream has a DO of 6 mg/l and a flow of 50 cfs. How many pounds per day of oxygen are

available for waste assimilation, if a 5 mg/l residual is desired? 3. If 7.0 cfs is flowing through a 24 inch diameter pipe, what is the velocity of flow in fps? 4. A polishing pond in 100 feet X 200 feet X 3 feet deep. It is required to dose this pond with

sodium nitrate. Using the following assumption: NaNO2 is 50% available oxygen by weight. It is required to provide 4 ppm of oxygen, By addition of NaNO3. How many pounds of NaNo3 will be required? 5. A plant discharges 05mgd of 25mg/l BOD. The receiving stream has a flow of 20 mgd and

an upstream BOD of 4 mg/l. Assuming even dispersion, what would be the downstream BOD?

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6. Given the following information, how many gallons of primary sludge containing 5 % solids must be pumped daily? Flow 3 mgd, primary influent 200 mg/l of suspended solids, primary effluent 100 mg/l of suspended solids?

7. A trickling filter is 100 ft in diameter and 6 ft deep and received .7 mgd with a BOD of 200

mg/l. What is the BOD loading in pounds per day per 1,000 cu feet of filter media? 8. What is the final BOD in the effluent of an activated sludge plant whose unit removal

efficiencies based on applied BOD are: Primary clarifier 35% Aeration basin 80% Secondary clarifier 20% Influent BOD is 200 mg/l 9. You have a raw sewage flow of 2 MGD entering your treatment system with an average

BOD of 170 ppm. 0.8 MGD of the total flow is caused by infiltration, due to poor sewer construction. After repairs are made, the infiltration is reduced by 70%. After repairs, what would you expect the average raw sewage BOD to be?

10. Determine the specific gravity of a sludge, given the following data: Weight of clean, empty jar = 390 g Weight of jar filled with water = 920 g Weight of jar filled with sludge = 941 g

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11. You have been authorized to disperse a larvicide on a stabilization pond at a rate of 15lb/10,000 sq ft of surface area. The larvicide weighs 8.34 lbs per gallon. The pond is 7 acres, with a 3 foot depth. How many gallons should be spread on the pont?

12. In order to provide 3 hours detention in a secondary clarifier at a 6 mgd rate, what tank

capacity, in cubic feet, is needed? 13. The solids in a digester amount to 10% when sludge is withdrawn to sand beds. At a later

date, the sludge cake has decreased to ½ its original volume. What is the % of solids? 14. The manager instructs you to see that flow proportional samples are taken every hour. The

flow at sampling times was 2.3 mg, 1.7 mg, 1.2 mg, 1.2 mg, 1.6 mg, and 2.0 mg. If the composite sample size is to be two liters, what should the first and last sample size be based on the above?

15. Assuming that it takes 1,000 cu/ft of air per pound of BOD per day added to an aeration

basin, and the flow is 2 mgd with an influent of 140 mg/l of BOD, how many cu/ft of air is needed per minute?

16. A 52 foot diameter circular clarifier has peripheral effluent weirs one foot from the walls. If

the surface loading is 800 g/d/sq ft, what is the weir loading in gallons per day per lineal foot?

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17. A one cylinder piston pump with an 8 inch bore and 5 inch stroke pumps 60 cycles per minute. How long must the pump be operated to pump 2,000 gallons of sludge?

18. A municipality has an average flow of 0.85 mgd, with an influent BOD of 200 mg/l, and an

effluent BOD of 25 mg/l. What is the plant’s population equivalent, based on BOD? 19. A digester with a volume of 20,000 cu/ft receives 1,700 dry pounds of raw sludge per day,

with a volatile content of 60%. What is the digester loading in pounds of volatile solids/day/1,000 cu ft.

20. Given a sewage treatment plant, utilizing a high rate trickling filter with continuous

recirculation from the trickling filter effluent to the trickling filter influent, actual conditions are as follows:

Filter 50 feet in diameter Depth 6 feet media depth Average Daily Flow 0.5 MGD Recirculation 1:1 BOD of primary effluent 140 mg/l Area – 1962 sq/ft 0.045 ac CALCULATE

a. The hydraulic loading on filter in gal/day/sq ft

b. BOD or biological loading in pounds/1000 cu/ft

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21. An 8-inch pipe is flowing at 400 gpm. What is the velocity in fps? 22. A 12-inch pipe conveys sewage at 2.76 fps. What is the flow express in MGD? 23. Your sewage billing rate structure is 115% of the water service rate. The water service rate

is $10.65 for the first 2,500 gallons a month, and then $3.50 for every thousand gallons of water or part thereof up to 10,000 gallons a month. A customer comes in with a sewage bill for $23.50 for 4,500 gallons of water usage. Based on your sewage service rate, what refund (or credit) is due this customer, if any?

24. Your DMR requires 1/7 (weekly) analysis for fecal coliform. The M. F. results for June

were: 180, 8,000, 400, and 10 organisms per 100 ml of sample. What is the monthly average geometrical mean?

25. A chemical cost $125.00 per 1,000 pounds. What is the daily cost of this chemical if it is

dosed at 2 mg/l into an average flow of 4 mgd? 26. Calculate a very well operating activated sludge treatment works effluent BOD based on the

following information: Initial DO of diluted sample = 8.3 mg/l, DO of incubated sample after 5 days = 4.5 mg/l, DO depletion in blank after 5 days = 0.1mg/l, bottle volume = 300 ml, sample volume = 50 ml.

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27. The influent raw sewage flow to a high rate trickling filter is 3.2 mgd. The recirculation rate is 150% of the works influent flow. What is the total flow, in mgd, through the trickling filter?

28. Given the following data, calculate the MLVSS in mg/l for a 100 ml sample.

1. Buchner fullel filter weight = 0.7822 grams 2. Filter and dish (filter is made on non-volatile fabric) after ignition = 2.8932 grams 3. Filter, dish, and solids after drying = 2.9950 grams 4. Dish weight = 2.000 grams

29. 15,000 gallons of 4% primary sludge are pumped to a mechanical thickener which concentrates this sludge to 7,000 gallons, What is the % of sludge concentration of the thickened sludge?

30. A casserole dish with sludge weighs 25.87 grams. The casserole weighs 8.47 grams.

The casserole and sludge after drying weights 10.47 grams. What is the % of total solids?

31. 90 cubic feet of sludge contains 3% solids. If the sludge is concentrated to 7% solids,

how many cubic feet of water are lost?

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Sept 04

EQUIVALENTS

1 foot (>) = 12 inches (A) 1 mile = 5,280 feet 1 acre = 43, 560 square feet 1 cubic yard = 27 cubic feet 1 cubic feet (ft.3) = 7.48 gallons = 62.4 pounds Metric Conversions 1 gallon of water = 8.34 pounds 1 in = 2.54 cm 1 day = 24 hours or 1,440 minutes or 86,400 seconds 1 Meter = 100cm 1 MGD = 694 gallons/minute 1 gal = 3.785 liters or 3,785 milliliters 1 MGD - 1.545 cu. feet/sec or ft.3/sec 1 liter = 1,000 milliliters 1 milligram/liter = 1 part per million 1 gram = 1,000 milligrams 1% = 10,000 ppm Average BOD/capita/day = 0.17 lbs 1 kilogram = 1,000 grams Average suspended solids/capita/day = 0.2 lbs 1 pound = 453.6 grams or 0.4536 kg Assume 3.5 persons to a single family residence Assume 100/gallon/capita/day for average daily flow π (pi) = 3.14

FORMULAS

Class 1: lbs = MGD x 8.34 x ppm mg/l = lbs Area of a Rectangle (MGD x 8.34) Area, sq feet = L x W MGD = lbs Volume of a Rectangular Tank (ppm x 8.34) Vol. cu. ft = L x W x Depth DETENTION TIME (hrs) = (Volume, gal. x 24)

flow, gpd Area of a Circle Percent (%) = PART x 100

Area, sq. ft. = 0.785 x (D ft)2 = πR2 WHOLE Volume of a Cylinder

Vol., cu. ft. = 0.785 (D ft)2 x (height, ft.) Efficiency (Percent) Centigrade (°C) = (°F - 32) x .555

% Removal = Eff % = (In - Out) x 100 Fahrenheit (°F) = (°C x 1.8) + 32 In

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Class II: Sludge dewatering V1 x P1 = V2 x P2 V1 = Original Volume Conc. (Mg/l) = Weight, gr x 1,000,000 V2 = New Volume (amount remaining) Sample vol., ml P1 = Original Percentage Sludge P2 = New Percentage Sludge

C = π x D Q = VA Q = flow (cfs) Composite Samples: V = Velocity (ft/sec) Total sample volume = Multiplier A = Cross sectional area (ft2) Total flow

BOD mg/l = (DO1 - DO2) x 300 SVI = 30 min. Settle sludge vol x 1,000

Sample vol ml MLSS mg/l Surface Loading Rate = Flow, gpd = Gallons/sq. ft./day

Area of tank in sq. ft. Weir Overflow Rate = Flow, gpd = Gallons/LF/day Length of weir in lineal feet Class III: 1 psi = 2.31 ft of water 1 hp = 746 watts or 0.746 KW F/M Ratio = lbs BOD entering aeration basin per pay lbs MLVSS in aeration basin DEFINTIONS

F/M Food to microorganism ratio Sludge Age = lbs MLSS in aeration basin VS Volatile solids

lbs aeration basin influent SS per day MLSS Mixed liquor suspended solids MLVSS Mixed liquor volatile suspended solids

MCRT = lbs MLSS under aeration SVI Sludge volume index (lbs SS wasted + lbs SS in effluent) RSF Return sludge flow

Brake Horsepower = gpm x total dynamic head x specific gravity

3960 x pump efficiency Motor Horsepower = Brake HP

Motor Efficiency % VS Reduction = raw VS - digested VS x 100 (use decimal equalivents)

raw VS - (raw VS x digested VS) RAS FLOW = 30 min setteable solids, ml x influent flow

supernatant, ml

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CLASS II REVIEW QUESTIONS ANSERWER SHEET

1. D 11. D. 21. C 31. F 2. C 12. E 22 F 32 D 3. C 13. B 23. B 33. C 4. B 14. B 24. C 34. D 5. D 15. E 25. D 35. B 6. D 16. D 26. A 36. E 7. D 17. E 27. E 37. C 8. C 18. C 28. C 38. C 9. C 19. A 29. D 39. D 10. B 20. E 30. D 40. D

1. 74.75% 11. 54.84 gal 21 2.55 fps 2. 270 lbs 12. 100,267.37 cu/ft 22. 1.40 mGD or 750,000 gal 23. $3.20 3. 2.229 fps 13. 20% 24. 275FC/100 ml 4. 29.88 lbs 14. 460 ml, 400 ml 25. $8.34 5. 4.512 mg/l 15. 1621 cfm 26. 22.8 mg/l 6. 6000 gal 16. 10,000 gal (or 10,816) 27. 8 MGD 7. 24.8 lbs 17. 30.5 min 28. 1018 mg/l 8. 20.8 mg/l 18. 8340 29. 8.57% 9. 236 mg/l 19. 51 lbs 30. 11.49% 10. 1.0396 20. a. 22.22 g/d/sq ft 31 51.43 cu ft b. 49.5 lbs/1000 cu ft

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