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wastewater test quiz


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Grit is mainly:

? Inorganic material
? Organic material
? Total suspended solids
? Volatile solids
Inorganic material
This material does not provide any food value to the biology and only takes up valuable tank space. It is essential to remove grit from the raw wastewater to protect pipe elbows, pump impellers and other internal surfaces from pitting and erosion
What does SOR mean (associated with primary clarification)?

? Standard Operating Regime
? Sand Organic Rut
? Surface Operating Rotation
? Surface Overflow Rate
Surface Overflow Rate
This measures the number of gallons per day that are applied to the clarifier for every square foot of the clarifier surface area (gpd/ft2)
The main purpose of primary treatment is to remove:

? Chlorine
? Ammonia
? Inorganic material
Typical primary treatment removes less of the influent CBOD5 as compared to the removal rate of the influent TSS
What is the basic purpose for the grit removal system?

? To protect the valuable capacity of tanks and process units (by not filling them with grit).
? To protect downstream equipment, pipe elbows, valve seats, pump impellers, and othe
To protect downstream equipment, pipe elbows, valve seats, pump impellers, and other components.from wear and erosion.
Protection of equipment components is always a good investment
What is the guideline velocity number for proper grit removal?

? 1.0 fps
? 1.5 fpm
? 1.0 fpm
? 1.0 rpm
1.0 fps
Less than 1.0 fps (feet per second) will also remove organic material with the grit, and create odors in the storage container. Greater than 1.0 fps may allow grit to pass through the grit chamber
Screenings debris is mainly:

? Inorganic material
? Organic material
? Total suspended solids
? Egg shells
Organic material
Most material captured and removed by a bar screen is organic ... volatile
What does H2S smell like at high concentrations?

? Rotten eggs
? Anaerobic sludge
? Sulfuric acid
? No smell
No smell
There is no smell because the high concentration of H2S basically deadens the sense of smell (olfactory fatigue).
What is H2S?

? Hydrogen peroxide
? Hydrogen sulfide
? Sulfuric acid
? Hydrogen sulfate
Hydrogen sulfide
Hydrogen peroxide is H2O2. Sulfuric acid is H2SO4
What is a typical range for an SOR within a primary clarifier?

? 1 to 2 Hours
? 100 to 200 gpd/ft
? 400 to 550 degrees C
? 800 to 1,000 gpd/ft2
800 to 1,000 gpd/ft2
Hydraulic loading rates are typically higher in primary clarifiers than secondary clarifiers
Which principle does the activated carbon system use for odor control?

? Absorption
? Adsorption
? Desorption
? Sequestering
Adsorption is like stuff sticking to fly paper. Carbon has a large surface area allowing odor compounds to get externally trapped (adsorbed).
What does H2S smell like at low concentrations?

? Rotten eggs
? Anaerobic sludge
? Sulfuric acid
No smell
Rotten eggs
It's easy to initially smell low concentrations of H2S ... it smells real bad! Rotten eggs is an awful odor ... try it, you'll hate it!
What does this formula represent?

(IN - OUT) ÷ IN x 100 = %

? Detention Time
? Removal Efficiency
? Loading Rate
Removal Efficiency
This formula will calculate removal efficiency of most constituents ... TSS, CBOD5, TN, TP, etc
What does H2S turn into that causes the damage to concrete and metal?

? Hydrogen peroxide
? Hydrogen sulfide
? Sulfuric acid
? Hydrogen
Sulfuric acid
It's the acidic condition from the sulfuric acid that causes damage to concrete and metal.
There once was a chemist ... a chemist no more ... thought he drank water ... but drank H2SO4
Which chemical is typically used to regenerate the carbon bed of an activated carbon odor control system?

? Alum
? Acid
? Sodium hydroxide
? Methanol
Sodium hydroxide
The addition of caustic to a bed of activated carbon, elevating the pH to about 12, acts to desorb H2S from the media.
Associated with primary clarifier scum, what does FOG mean?

? Fully Organic Gold
? Far Oily Gate
? Fat Oil Grease
? Fat Old Guy
Fat Oil Grease
It just does!
What is the basic purpose for the screenings removal process?

? To stop bacteria growth
? To protect downstream pipes, pumps, valves, and other components from plugging.
? For sample testing
? To remove inorganic mater
To remove inorganic
Screenings removal is essential to maintain maximum operational capacity of pumps and pipes.
What percent of the settleable solids are typically removed through primary clarification?

? 20 to 30%
? 40 to 60%
? 25 to 30%
? 100%
The standard definition of a settleable solid are those solids that settle within 60 minutes.
Typical primary clarification provides more than 1 hour of detention time ... hence, all settleable solids will settle in the primary clarifier.
A screenings removal unit with less than ½ inch openings is known as:

? A coarse bar rack
? A manual bar screen
? A fine bar/filter screen
? A comminutor
A fine bar/filter screen
These units are typically automated and controlled by timers or differential head across the screen
Which chemical is typically used for wet scrubber odor control at the headworks of a plant?

? Acid
? Polymer
? Sulfur dioxide
? Sodium hydroxide
Sodium hydroxide
Headworks odors are mainly H2S based. This requires a high pH to remove the sulfides. Sodium hydroxide (caustic) is the only chemical on the list that is capable of increasing the pH necessary for absorption of H2S in a wet scrubber.
Which chemical is typically used for wet scrubber odor control at the solids handling portion of a plant?

? Acid
? Polymer
? Caustic soda
? Sodium hydroxide
Solids handling odors are mainly ammonia based. It typically requires low pH to accomplish absorption in a wet scrubber treating odors from a solids handling process (especially with anaerobic digestion).
Which principle does the wet scrubber use for odor control?

? Absorption
? Adsorption
? Desorption
? Sequestering
The odors are basically "soaked" into and held in the liquid stream ... like water soaks into a sponge. This usually requires a pH of at least 9.0 to 10.0 to accomplish absorption of H2S in a wet scrubber.
Is H2S lighter or heavier than air?
? lighter
? heavier
? same weight
Hydrogen sulfide has a higher specific gravity (1.192) as compared to air (1.0). That's why H2S settles to the bottom of a space.
Where is a typical location to pump primary sludge?

? Aerobic Digestion
? Secondary Clarifier
? Anaerobic Digestion
? Gravity Belt Thickener
Anaerobic Digestion
Most plants with primary clarifiers also have anaerobic digestion to accomplish stabilization of the primary sludge.
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
? Decrease the amount of primary sludge withdrawal
? Stop pumping primary
Increase the amount of primary sludge withdrawal
Gas and rising sludge in a primary clarifier is usually caused by anaerobic conditions in the sludge blanket.
Increasing the amount of sludge removed from the clarifier will help to reduce the production of anaerobic gases.
What method of grit removal is the Pista Grit system?

? Free vortex
? Low velocity
? High velocity
? Forced vortex
Forced vortex
Forced vortex means that is has a mechanical paddle drive system to create the vortex action. Free vortex uses the entry angle to create a vortex without any moving equipment.
What is a typical detention time for a primary clarifier?

? 4 to 8 Hours
? 1 to 2 Hours
? 30 to 45 Minutes
? 15 Minutes at Peak Flow
1 to 2 Hours
1 to 2 hours is the standard detention time of a primary clarifier.
A typical secondary clarifier detention time is about 2 to 4 hours.
Typical primary clarification removes TSS in which range?

? 20 to 30%
? 40 to 60%
? 25 to 30%
? 100%
40 to 60%
One of the main purposes of primary treatment is to allow the downstream biological treatment process to be down-sized ... due to the removal of TSS and CBOD5 from the influent wastewater.
Typical removal efficiency for CBOD5 is about 25 to 30% of the influent wastewater.
Aerated grit chambers usually utilize what type of aeration system?

? Mechanical
? Diffused
? Transverse
? Low speed mixer
The diffusers are typically located along one side of the tank creating a rolling action across the tank's width.
Which is true?

? Activated carbon is very selective in the removal of odor contaminants
? Activated carbon is very non-selective in the removal of odor contaminants
Activated carbon is very non-selective in the removal of odor contaminants
Non-selective means that it will remove a wide array of odor compounds. The trade-off is that carbon can become "spent" very quickly because it removes various odor species.
What device is more commonly used for separation of grit slurry?

? Aerated grit chamber
? Clarifier
? Cyclone classifier
? Air lift
Cyclone classifier
These devices basically spin the grit out of the slurry using centrifugal force.
What bacterial activity measurement is expressed as mg/L/hr?

? Respiration rate (RR)
? Dissolved oxygen (D.O.)
? Settleometer
? Oxygen uptake rate (OUR)
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
What type of phosphorus is soluble and not particulate?

? Poly-phosphate
? Organic-phosphate
? Ortho-phosphate
? Agoro-phosphate
This type of phosphorus usually requires some form of chemical treatment to achieve low levels
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%
? 5,160 lbs/day
? 1,548 lbs/day
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.
Which two flow streams typically combine together to make-up mixed liquor?

? Influent and secondary effluent
? Influent and primary effluent
? Primary effluent and waste activated sludge
? Primary effluent and return activat
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).
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?

? High rate aeration
? Conventional aeration
? Endogenous respiration
? Pure oxygen
Conventional aeration
This is know as the declining growth phase ... about the middle of the growth curve.
What typically happens to the activity rate of the microorganisms as the temperature of the wastewater decreases?

? It speeds up
? It slows down
? Temperature of the wastewater has nothing to do with activity rate of the bugs
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
Which two laboratory analyses are required to calculate the F/M ratio?

? Influent CBOD5 and MLSS
? Effluent CBOD5 and TSS
? MLVSS and influent TOC
? Influent CBOD5 and MLVSS
Influent CBOD5 and MLVSS
F is food, or CBOD5; and M is mass or volatile microorganisms
What is the correct incubation time and temperature for the BOD test?

? 5 days at 20°F
? 5 days at 20°C
? 20 days at 5°C
? 5 days at 68°C
5 days at 20°C
This is the standard time and temperature for CBOD5 values that are used for F/M ratio calculation
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?

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.
What is it called when mixed liquor never settles properly and remains either suspended or rising in the secondary clarifier?

? Rising sludge
? Bulking sludge
? Sludge blanket
? Nitrification
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.
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?

? Subnatant
? Effluent
? Filtrate
? 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).
Your score is 18%.
What process control parameter is the result of aeration total solids inventory divided by total solids removed from the process?

? Gould sludge age (GSA)
? Solids retention time (SRT)
? Mean cell residence time (MCRT)
? Slu
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
Which aeration system is typically operated in the endogenous respiration growth phase?

? Conventional activated sludge
? High rate aeration
? Extended aeration
? Log growth
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.
Which type of bacteria must have free dissolved oxygen to survive?

? Anaerobic
? Anoxic
? Facultative
? Aerobic
This oxygen must be supplied from an external source of energy ... like mechanical aerators or diffused aeration with blowers
What type of BOD is measured when the sample being analyzed is first filtered?

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
Which statement best describes denitrification?
? NH3 + O2 = NO2
? NO2 + carbon = NH3
? NO3 + O2 = NO2
? NO3 + carbon = N2
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).
What is another way of saying mg/L?

? ppm
? 7.48 gals per ft3
? 8.34 lbs per million gallons
? Both a and c
Both a and c
ppm and 8.34 lbs per million gallons are both the same as mg/L.
One gallon per million gallons is 1 ppm.
What condition can result in sludge on the surface of a secondary clarifier typically caused by a septic environment?

? Bulking sludge
? High rate aeration
? Rising sludge
? Over-
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.
What is an intermediate oxidation state between ammonia nitrogen (NH3) and nitrate nitrogen (NO3)?

? CO2
? 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.
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
? Under-loaded
? F/M ratio has nothing to do wi
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
Which growth phase provides the best oxygen utilization efficiency . . . lowest pounds of oxygen per pound of CBOD5 converted?

? Endogenous respiration
? Declining growth
? Extended aeration
? Log growth
Log growth
Typically, in this log growth phase, the bugs are in their most active state and the oxygen utilization efficiency is at its most optimum
What is a typical SRT in the log growth phase?

? High – above 15 days
? Moderate – about 7 days
? Low – below 3 days
? It can’t be measured
Low – below 3 days
Log growth typically has a low MLSS concentration and a high CBOD5 ratio.
This means the F/M ratio is high and the SRT is low.
Which parameter best describes the balance of food to microorganisms?

? F/M
F is the food (or CBOD5) available to the carbon-eating bugs; and M is the mass or volatile microorganisms available to eat the food.
F/M ratio is basically the diet of the bugs!
Which best describes sludge volume index?

? Numerical indicator of bug population
? Volume-to-weight ratio of mixed liquor
? Volume-to volume ratio of mixed liquor
? Removal efficiency of BOD
Volume-to volume ratio of mixed liquor
SVI is a numerical indicator of the settling rate of MLSS.
By definition, the SVI is the volume of sludge in ml occupied by one gram of mixed liquor.
Differently said, SVI is the volume-to-weight ratio of the mixed liquor.
Which activated sludge process re-aerates RAS before being introduced into the influent wastewater?

? Step feed
? Complete mix
? Contact stabilization
? Plug Flow
Contact stabilization
The reaeration tank aerates the RAS flow stream and then is displaced into the contact tank
Which age parameter utilizes the pounds/day of influent TSS entering the aeration tank?

? F/M ratio
Gould Sludge Age (GSA) does not consider any CBOD5 or WAS values in the
Which condition may indicate too much food is still available in the MLSS leaving the aeration tank?

? Low OUR/RR in aeration inlet
? High OUR/RR in aeration inlet
? Low OUR/RR in aeration outlet
? High OUR/RR in aeration ou
High OUR/RR in aeration outlet
The oxygen uptake rate (OUR) typically remains high when CBOD5 (food) is still available in the aeration tank outlet
Which growth phase does the stabilizer tank of the contact stabilization process typically operate in?

? Log growth to declining
? Declining growth to endogenous
? Endogenous respiration to log
? Filamentous
Declining growth to endogenous
Depending on the MLSS concentration, F/M ratio and the SRT, the stabilizer tank bugs could be in the old declining growth to young endogenous respiration phase.
What test result is necessary to convert OUR to RR?

? D.O.
The respiration rate (RR) is calculated by dividing the OUR, mg/l/hr by the mixed liquor volatile suspended solids, MLVSS,in gm/l.
The units for RR are mg of oxygen per gm of volatile bug per hour of time.
What is a typical F/M ratio range in the declining growth phase?

? 0.7 to 1.0
? 0.2 to 0.5
? 0.05 to 0.15
? 0.6 to 0.75
0.2 to 0.5
Typically, in the declining growth phase, MLSS concentration is about 2,000 to 3,000 ppm, SRT is about 4 to 8 days and F/M ratio is about 0.2 to 0.5.
The F/M ratio value reducs as the growth phase moves more to the right on the curve ... more toward endogenous.

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