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67 Cards in this Set
- Front
- Back
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True or False: As an operator, you are responsible to your employer for maintaining an economical and efficient operating facility. |
True |
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True or False: All organic materials have one thing in common - They all contain basic minerals. |
False |
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Best Answer: What is an inorganic waste? |
Waste material such as sand, salt, iron or calcium. |
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Best Answer: Why are ammonia and hydrogen sulfide undesirable in receiving waters? |
They are odorous gases. |
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True or False: Both aerobic and anaerobic sludge digestion process produce stabilized or digested solids that ultimately must be disposed of in the environment. |
True |
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True or False: In a preventive maintenance program the failure of the operator to record the work he has done is an example of poor operations. |
True |
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True or False: When draining a tank the ground water level should be down far enough so that the tank will not float or rupture while empty. |
True |
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Associated with primary clarifier scum, what does FOG mean?
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Fat Oil Grease
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Where is a typical location to pump primary sludge?
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Anaerobic Digestion
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Screenings debris is mainly:
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Organic material
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Which principle does the activated carbon system use for odor control?
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Adsorption
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What device is more commonly used for separation of grit slurry?
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Cyclone classifier
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What does H2S smell like at high concentrations?
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No smell
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Which chemical is typically used for wet scrubber odor control at the headworks of a plant?
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Sodium hydroxide
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What does H2S smell like at low concentrations?
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Rotten eggs
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Typical primary clarification removes TSS in which range?
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40 to 60%
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What method of grit removal is the Pista Grit system?
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Forced vortex
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Which principle does the wet scrubber use for odor control?
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Absorption
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What percent of the settleable solids are typically removed through primary clarification?
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100%
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What is the guideline velocity number for proper grit removal? |
1.0 fps |
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What adjustment is generally necessary when gas and/or solids rise to the surface of a primary clarifier? |
Increase the amount of primary sludge withdrawal |
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A screenings removal unit with less than ½ inch openings is known as:
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A fine bar/filter screen
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Is H2S lighter or heavier than air?
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heavier
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What does H2S turn into that causes the damage to concrete and metal? |
Sulfuric acid |
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What is a typical detention time for a primary clarifier? |
1 to 2 Hours |
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What is the basic purpose for the grit removal system? |
To protect downstream equipment, pipe elbows, valve seats, pump impellers, and other components.from wear and erosion. |
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What does SOR mean (associated with primary clarification)? |
Surface Overflow Rate |
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What is H2S? |
Hydrogen sulfide
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Aerated grit chambers usually utilize what type of aeration system? |
Diffused |
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What is the basic purpose for the screenings removal process? |
To protect downstream pipes, pumps, valves, and other components from plugging. |
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What does this formula represent?(IN - OUT) ÷ IN x 100 = % |
Removal Efficiency |
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Which chemical is typically used for wet scrubber odor control at the solids handling portion of a plant? |
Acid |
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Which chemical is typically used to regenerate the carbon bed of an activated carbon odor control system? |
Sodium hydroxide
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What is a typical range for an SOR within a primary clarifier? |
800 to 1,000 gpd/ft2 |
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The main purpose of primary treatment is to remove: |
TSS & CBOD5
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Grit is mainly:
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Inorganic material
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What type of phosphorus is soluble and not particulate? |
Ortho-phosphate This type of phosphorus usually requires some form of chemical treatment to achieve low levels. |
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What condition can result in sludge on the surface of a secondary clarifier typically caused by a septic environment? |
Rising sludge Rising sludge originally settled properly and then gas caused it to rise to the surface.This may indicate a lack of D.O. in the aeration system, an RAS rate that is too low, or plugged draft tubes or broken plows. |
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Which type of bacteria must have free dissolved oxygen to survive? |
Aerobic This oxygen must be supplied from an external source of energy ... like mechanical aerators or diffused aeration with blowers. |
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Given the following data, what is the CBOD5 loading on the aeration system of this facility? - Plant flow is 2.75 mgd - Influent CBOD5 is 225 mg/L - Primary clarifier CBOD5 removal is 30% |
3,612 lbs/day (225 mg/L x 0.7) x 2.75 mgd x 8.34 lbs/gal Note: 0.7, or 70% is the remaining CBOD5 that leaves the primary clarifier and enters the aeration system. |
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What is an intermediate oxidation state between ammonia nitrogen (NH3) and nitrate nitrogen (NO3)? |
NO2 Nitrite is usually very unstable and "wants" to be something else ... typically either nitrate or free nitrogen gas.Nitrite stabilization can result in toxic kill of microorganisms, or at the very least, a high demand for chlorine. |
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Which type of activated sludge process typically has an F/M ratio of about 0.2 to 0.5 and an SRT of about 5 to 15 days? |
Conventional aeration This is know as the declining growth phase ... about the middle of the growth curve. |
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What is another way of saying mg/L? |
7.48 gals per ft3 & 8.34 lbs per million gallons ppm and 8.34 lbs per million gallons are both the same as mg/L. One gallon per million gallons is 1 ppm. |
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Which flow pattern typically combines the influent wastewater (or primary effluent) and RAS before it enters the beginning of a rectangular aeration tank. The combined flow then travels straight through the tank and leaves at the other end?
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Plug flow
All flow (influent and RAS) enters the beginning of the aeration tank and "plugs" through the tank's length being displaced from the end of the tank. |
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Which aeration system is typically operated in the endogenous respiration growth phase? |
Extended aeration This is on the far right side of the growth curve where older bugs use more oxygen to break down CBOD5.The MLSS concentration in an extended aeration process can typically be very high. |
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Which two laboratory analyses are required to calculate the F/M ratio? |
Influent CBOD5 and MLVSS F is food, or CBOD5; and M is mass or volatile microorganisms. |
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What typically happens to the activity rate of the microorganisms as the temperature of the wastewater decreases? |
It slows down Just like us, when the temperature gets colder we move slower!Bacterial activity rate doubles with every 10 degree C increase in temperature. |
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What process control parameter is the result of aeration total solids inventory divided by total solids removed from the process? |
Solids retention time (SRT) SRT is usually based on total solids and MCRT is based on volatile solids.That may change depending on which book you read! |
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A high rate aeration system (not pure oxygen) typically has a low MLSS concentration and high F/M ratio … is this system considered to be over-loaded or under-loaded? |
Over-loaded Loading refers to the amount of CBOD5 entering the aeration system ... and not the amount of solids in the system.So, an overloaded system typically has high F/M ratio. |
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What type of BOD is measured when the sample being analyzed is first filtered? |
SBOD The "S" stands for soluble.When the sample is filtered, the BOD value in the filtrate is typically lower than the BOD value of the unfiltered sample. |
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Which two flow streams typically combine together to make-up mixed liquor? |
Primary effluent and return activated sludge In plants without primary treatment, mixed liquor suspended solids (MLSS) is a combination of influent wastewater and return activated sludge (RAS). |
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What is the correct incubation time and temperature for the BOD test? |
5 days at 20°C This is the standard time and temperature for CBOD5 values that are used for F/M ratio calculations. |
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What is it called when mixed liquor never settles properly and remains either suspended or rising in the secondary clarifier? |
Bulking sludge Bulking is different from rising sludge because it never settles to start with.However, rising sludge originally settled, and then for some reason (typically caused by septic gas), rose to the surface. |
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What bacterial activity measurement is expressed as mg/L/hr? |
Oxygen uptake rate (OUR) The OUR identifies the amount of oxygen used per unit of time.It is referred to as a quantitative test (the quantity of oxygen used).However, OUR is not related to the quality of bugs in the system. That would be the RR test. |
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What term is used to describe liquid that is removed from a digester, between an upper layer of scum and a lower blanket of sludge? |
Supernatant Supernatant is typically removed from either an aerobic or anaerobic digester.Liquid that is removed from the underside of a blanket of floating sludge is referred to a subnatant (like in a dissolved air flotation [DAF] process). |
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Which statement best describes denitrification? |
NO3 + carbon = N2 Denitrification converts nitrates into free nitrogen gas that is displaced into the atmosphere.This is an anoxic process that requires active bugs, low-to-no dissolved oxygen and a source of carbon (CBOD5). |
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What is the detention time in a rectangular clarifier that is 225 feet long, 45 feet wide, and 17 feet deep … when the flow is 3.7 mgd? |
8.4 hours Detention Time, hours= length, ft. x width, ft. x depth, ft. x 7.48 gal/ft3 ÷ 1,000,000 x 24 hrs/day ÷ flow, mgd= 225 ft. x 45 ft. x 17 ft. x 7.48 ÷ 1,000,000 x 24 ÷ 3.7 mgd= 8.4 hours |
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A clarifier has a depth of 12 feet and a diameter of 100 feet. What is the surface area of this tank in square feet? |
7,850 sq.ft Surface Area, ft2= π r2 of a round tankradius = 100 feet diameter ÷ 2= 50 feetNote: diameter ÷ 2 = radius= 3.14 x 50 ft x 50 ft.= 7,850 ft2 |
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A circular clarifier treats a flow of 1.7 mgd. The diameter is 35 feet and the depth is 17 feet. What is the surface loading? |
1,768 gpd/sq.ft. Surface Loading, gpd/ft2= gpd flow ÷ surface area, ft2= mgd x 1,000,000 ÷ π r2 = 1,700,000 gpd ÷ 3.14 x 17.5 ft. x 17.5 ft.= 1,700,000 ÷ 961.6 ft2 = 1,768 gpd/ft2 |
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A flow of 825 gpm is pumped against a total head of 430 feet by a pump with an efficiency of 55% and a motor with an efficiency of 85%. What is the total horsepower?
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192 Hp
Hp= gpm x TDH x 8.34 ÷ 33,000 ÷ % pump eff. ÷ % motor eff.= 8.25 x 430 x 8.34 ÷ 33,000 ÷ 0.55 ÷ 0.85= 192 Hp
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If water flows through a 6-inch pipe at a rate of 3.5 cubic feet per second (cfs), what is the velocity? |
17.83 ft per sec fps = cfs ÷ ft2= 3.5 cfs ÷ π r 2= 3.5 ÷ 3.14 x 0.25 x 0.25= 17.83 fps |
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At what pH is a liquid considered to be neutral? |
7.0 The pH scale ranges from 0 to 14. Zero to 6.9 is acidic; 7.0 is neutral; 7.1 to 14.0 is basic (Alkaline). |
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A flow of 4.7 mgd flows through a clarifier that is 22 feet high and has an 18 foot radius. What is the detention time in minutes? |
51 minutes Detention Time, minutes= π r2 x depth, ft. x 7.48 gal/ft3 ÷ 1,000,000 ÷ flow, mgd x 1,440 mins/day= 3.14 x 18 ft. x 18 ft. x 22 ft. x 7.48 ÷ 1,000,000 ÷ 4.7 mgd x 1,440 mins/day= 51.3 minutes |
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How many gallons of water is in a tank that is 74 feet in diameter and 37 feet high when the water is 29 feet deep? |
932,465 gallons Gals = π r2 x Depth, feet x 7.48 gal/cu ft.Radius = 74 feet ÷ 2 = 37 feetNote: diameter ÷ 2 = radiusGals = 3.14 x 37 ft. x 37 ft. x 29 ft. x 7.48 gal/cu ft.= 932,465 gals |
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A flow of 252,000 gpd is pumped against a total head of 57 yards. If the efficiency of the pump is 50% and the efficiency of the motor is 80% what is the horsepower? |
19 Hp
Hp= gpm x TDH x 8.34 ÷ 33,000 ÷ % pump eff. ÷ % motor eff.= 252,000 gpd ÷ 1,440= 175 gpm= 175 gpm x (57 yards x 3) x 8.34 ÷ 33,000 ÷ 0.5 ÷ 0.8= 19 Hp
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What should be the waist return sludge pumping rate in gallons per minute if a plant should be wasting 500 pounds per day and the concentration of return sludge is 5800 mg/L |
7 GPM
5800×8.34= 48372 500÷48372=.010MGD 0.010MGD×694GPM/MGD=6.94GPM |
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True or False Nutrients which enable vigorous growth of plants on land also enable vigorous growh of plants in water. |
True |
