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101 Cards in this Set
- Front
- Back
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Never raise or lower digester temperatures by more than? |
1 degree F per day |
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What three gases are produced in anaerobic digesters? |
Methane (ch4) carbon dioxide (co2) hydrogen sulfide (h2s) |
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What are two characteristics of well digested sludge? |
Ph of 7.0-7.2 and a leathery appearance |
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Most digesters operate at a temperature range of? |
95-98 |
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When operating properly a medium range digester will produce gas that is ____ methane. |
70% |
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Which of the following statements is true regarding pumping sludge to a digester?A. The solids concentration should be as high as possible.B. Pumping smaller volumes more often is easier on the process than pumping lots of sludge all at once.C. The overflow from the digester will return to the headworks of the plant.D. All of the above. |
D |
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How long does it take to stabilize sludge at the three temperature ranges for anaerobic digestors? |
Psychrophilic-50-120 days
Mesophilic-25-30 days
Thermophilic-5-12 days
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What is the solids loading rate for an anaerobic digester? |
.15 - .35lbs per day/cuft |
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What is the BTU value of digester gas? |
500-800 BTUS |
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The vertical pickets on a gravity thickener |
Aid in mixing and gas release |
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The sludge blanket in a gravity thickener should be: |
5-8 feet deep |
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As the sludge blanket depth increases: |
Detention time decreases |
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What are operational parameters for a gravity thickener? |
detention time, sludge blanket depth, and sludge withdrawal rate. |
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What is the detention time for Gravity thickners? |
1-2 days |
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What kind of pump is used for pumping primary sludge? |
Positive displacement pumps |
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Primary clarifiers should have a detention time of: |
2 hours |
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Primary clarifiers remove how much of settleable solids? |
90-95% |
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How much suspended solids do primary clarifiers remove? |
40-60% |
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The solids concentration in primary sludge should be: |
4-6% |
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What is the normal BOD removal efficiency in a primary clarifier? |
30-40% |
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What is the normal operating depth of a facultative pond? |
4-7 ft. |
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What supplies 70-80% of oxygen to bacteria in a facultative pond? |
Algae |
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What is the depth of an aerobic pond? |
3 ft |
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When will the ph be the lowest in a pond? |
Just before dawn |
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When will the ph be the highest in a pond? |
Late afternoon |
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What is the BOD loading rate for a facultative pond? |
20-35lbs per acre per day |
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What is the detention time for facultative ponds? |
30-60 days |
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Facultative lagoon levels should always maintain at least how many feet of water? |
4 feet |
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What can be done to recover from an organic overload on a pond? |
A. Increase recirculation B. Run ponds in parallel C. Add sodium nitrate |
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What is the BOD loading for a standard trickling filter? |
15-20 pounds per day |
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What is the hydraulic loading range for a standard trickling filter? |
1-4 mgd/acre (25-100 gpd/ft2). |
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What is the material that sloughs off the media of a trickling filter called? |
Zoogleal film |
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What should the effluent DO be in a trickling filter? |
1.5-2mg/l |
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Which of the following is a problem in trickling filters?
A. SnailsB. PondingC. Psychoda fliesD. All of the above |
D |
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How do you control filter flies and ponding in trickling filters? |
Increase recirculating rate |
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What is the BOD loading for a high rate trickling filter? |
40 - 60 lbs per day |
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Healthy growth on the first stage of an RBC will be: |
Gray |
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The DO in the last stage of a nitrification process in an RBC should be at least: |
4mg/l |
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How much BOD does a well operated activated sludge process remove? |
95 - 98% |
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The portion of the MLSS that is actually eating the incoming food is referred to as |
Mixed liquor volatile suspended solids (MLVSS) |
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The solids concentration (RAS/WAS) of an activated sludge process are? |
.5 - .8% or 5,000 - 8,000 mg/l |
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What can you do to maintain proper detention time as the flow drops in an activated sludge process? |
Increase RAS flow |
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What are two process control parameters used in a activated sludge process? |
F:M ratio and MCRT |
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Good settling sludge will have an SVI between? |
80 and 120 |
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What is the ideal D.O. range in an activated sludge process? |
2 - 4 mg/l |
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What is the ideal D.O. range in an activated sludge process? |
2 - 4 mg/l |
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The minimum DO is? |
1 -2 mg/l |
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MLSS In a conventional activated sludge process is? |
2,000 - 3,500 mg/l |
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What are three parameters that can be adjusted to maintain efficiency? |
Dissolved oxygen, RAS flows and WAS flows |
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Return sludge pump capacity should be what % of average daily flow? |
50 - 70 % |
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What type of activated sludge process does not have primary clarifiers? |
Extended aeration |
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What is the aeration basin detention time in conventional activated sludge processes? |
4-6 hours |
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What should the velocity be in an oxidation ditch? |
1.0 fps |
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Straggler floc would be found in: |
Young sludge |
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Wasting rates should never be changed by more than ___ at a time |
10% |
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What microorganisms are predominant in very old sludge? |
Rotifers |
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White crisp foam in the aeration basin indicates: |
A young sludge |
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How many pounds of oxygen does it take to convert 1 pound of ammonia to nitrates? |
4 - 6 pounds |
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If chlorine is used to oxidize ammonia the ratio will need to be: |
10:1 |
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Calcium Hypochlorite is what % available chlorine? |
60 - 70% |
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Chlorine gas can be lethal at what concentration? |
50ppm |
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A fusible plug melts at ? |
157 degrees |
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Take the rotameter reading at: |
The widest part of the float |
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What's the maximum gas feed rate of a 1 ton cylinder? |
400lbs/day |
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A 1-ton cylinder will have how many fusible plugs? |
6 |
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What two acids are formed when chlorine gas reacts with water? |
hydrochloric acid and hypochlorous acid. |
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Which three chemicals are formed when chlorine reacts with ammonia in water? |
monochloramine, dichloramine trichloramine |
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The maximum feed rate for a 150 lb. cylinder is: |
40lbs/day |
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A low vacuum in the system can be caused by: |
Clogged injector |
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Gas coming from an outside vent line would indicate a: |
Dirty Pressure Regulating Valve |
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What's the primary reason for a reciprocating pump failure? |
Clogged or fouled check valve |
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The chemical most often use to dechlorination wastewater effluent is: |
Sulfur dioxide |
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Dissolver oxygen meters must be calibrated? |
Everyday |
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A ph meter must be? |
Standardized before each use |
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What's the formula for MLSS testing? |
GramsX1,000,000/sample size |
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Which tests are run with grab samples? |
DO, PH, fecal coliform |
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Fecal coliform tests are incubated at: |
44.5o + 0.2 C |
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The maximum holding time for a proportional composite BOD sample is: |
48 hours |
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MLVSS samples must be ignited at? |
500 +/- 50o C |
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Fecal coliform colonies in the membrane filter test are: |
Blue |
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What's the most common positive displacement pump? |
Reciprocating pump |
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What's the purpose of a stuffing box? |
To keep water in and air out |
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What does the packing gland do? |
Tightens the packing |
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The lantern ring is aligned with? |
The seal water port |
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At sea level what's the absolute maximum negative suction head? |
33.8 ft |
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What are four factors in determining friction loss? |
Size of pipe Flow through the pipe Length of pipe C factor |
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A loss of shutoff head is most likely caused by ? |
an increase in recirculation inside the pump due to worn wear rings or worn impellers. |
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The best way to prevent loss of prime is to always design a pump installation with |
Positive suction head on the pump |
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If the pressure against a positive displacement pump increases: |
Flow stays the same |
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What happens when you increase the pressure on a centrifugal pump? |
Flow decreases |
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What is NPSH? |
Net positive suction head |
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The maximum pressure a centrifugal pump can generate is called: |
Shutoff head |
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For most pumping applications negative suction heads should never exceed? |
20 ft |
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For most pumping applications negative suction heads should never exceed? |
20 ft |
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Cavitation can be temporarily corrected by |
Throttling the discharge valve |
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Bearings are heat stabilized to |
250 degrees |
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If any two leads on a 3-phase motor are switched: |
It will run in the opposite direction |
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RTU stands for? |
Remote terminal unit |
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The alarm point for hydrogen sulfide gas is |
10 ppm |
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The alarm point for carbon monoxide is ? |
35 ppm |
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Ladders must extend at least ___ feet above the trench? |
3 |
