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wastewater quiz


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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.
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
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
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.
Your score is 25%.
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.
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!
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.
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 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 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.
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.
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.
Is H2S lighter or heavier than air?

? lighter
? heavier
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.
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 improve sludge dewatering
Protection of equipment components is always a good investment.
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 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.
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.
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.
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 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.
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.
What is H2S?

? Hydrogen peroxide
? Hydrogen sulfide
? Sulfuric acid
? Hydrogen sulfate
Hydrogen sulfide
Hydrogen peroxide is H2O2. Sulfuric acid is H2SO4
Typical primary clarification removes TSS in which range?

? 20 to 30%
? 40 to 60%
? 25 to 30%
? 100%
40 to 60%
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
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)
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).
What does H2S turn into that causes the damage to concrete and metal?

? Hydrogen peroxide
? Hydrogen sulfide
? Sulfuric acid
? Hydrogen sulfate
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
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 material
To protect downstream pipes, pumps, valves, and other components from plugging.
Screenings removal is essential to maintain maximum operational capacity of pumps and pipes.
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.
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 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.
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.
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 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).
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 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 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.
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 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-wasting
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
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).
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.
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 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 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 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 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.
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 calculations.
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
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 flow stream is typically the most concentrated (ppm) in the contact stabilization process?

? Stabilizer tank
? Contact tank
? Influent wastewater
Stabilizer tank
The Stabilizer concentration is about 4,000 to 8,000 ppm ... which is higher than any other location in the process
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.
What is a typical F/M ratio range in the endogenous respiration growth phase?

? 0.7 to 1.0
? 0.2 to 0.5
? 0.05 to 0.15
? 0.6 to 0.75
0.05 to 0.15
As the growth (activity) rate moves right on the growth curve, the available food value (CBOD5) is reduced and the calculated F/M ratio is lower.
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.
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!
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.
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.
Where is the highest demand for oxygen in a plug flow aeration tank?

? At the effluent weir
? In the middle of the tank
? Equally throughout the tank
? In the beginning of the tank
In the beginning of the tank
The beginning of the aeration tank usually has the highest concentration of CBOD5 and ammonia and the most potentially active microorganisms
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 is predominant in extended aeration?

? Declining growth
? Endogenous respiration
? Log growth
? Filamentous
Endogenous respiration
This growth phase is typical for activated sludge with high SRT and low F/M ratio
What typically happens to microorganisms when they are subjected to an excessive supply of food (CBOD5)?

? They grow and multiply
? Their growth slows down
? The demand for oxygen decreases
? The sludge yield decreases
They grow and multiply
If the growth rate is poor, but the F/M ratio is high, the cause will not be from a lack of food
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-weight 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
What is the typical oxygen utilization condition in the endogenous respiration growth phase?

? The utilization of oxygen is at its best
? The demand for oxygen is low
? The demand for oxygen is not affected by growth phase
The utilization of oxygen is at its poorest
Some of the oxygen in the endogenous respiration phase is consumed and does not result in conversion of CBOD5 or ammonia.
When the bugs are older, they typically need more oxygen to do the same amount of work ... compared to when they were younger.
What is typically the limiting factor in sustaining growth of microorganisms in the declining growth phase?

? Oxygen
? Time
? Food
? Volatile bugs
When sufficient CBOD5 is available, the growth rate of the bugs is typically sustained at a higher rate.
The declining growth phase typically does not have enough available CBOD5 to continue a high growth rate.
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 aeration mode is intended to dilute high demand influent loadings?

? Plug flow
? Step feed
? Complete mix
? Contact stabilization
Step feed
Step feed combines influent and RAS and introduces it across the length of the tank.
This dilutes the demand for oxygen throughout the tank.
Which conditions best describe potential filamentous over-growth (bulking)?

? High D.O. and low food
? High D.O. and high F/M ratio
? Low D.O. and low F/M ratio
? Zero D.O. and low SRT
Low D.O. and low F/M ratio
Because filamentous bacteria are strictly aerobic, they can out-compete heterotrophic bacteria for oxygen ... especially with low substrate (CBOD5) values.
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 calculation.
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.
Which conditions typically generate a larger volume of new cellular growth?

? High F/M with low D.O.
? Low F/M with high D.O.
? Low F/M with low D.O.
? High F/M with high D.O.
High F/M with high D.O.
This condition of high oxygen and high food availability typically creates the highest growth rate of heterotrophs and the highest sludge yield.
High new cell growth requires more wasting
If a plant had 75,000 pounds of MLSS in inventory, and desired to maintain a 7 day SRT, how many pounds/day of solids must be wasted from the system?

? 7,500 lbs/day
? 10,714 lbs/day
? 9,333 lbs/day
? 75,000 lbs/day
10,714 lbs/day
Pounds to waste is calculated by dividing the pounds inventory by the desired SRT.
75,000 pounds divided by 7 days
= 10,714 pounds to waste.
What type of floc is typically the result, and/or results in, the following characteristics: high F/M ratio, high food supply, young sludge, log growth phase, slow settling mixed liquor with excellent capture and clear effluent?

? Pin
Straggler floc is usually the result of over-loaded activated sludge (high CBOD5 concentrations, high F/M ratio and low SRT).
Pin floc is typically related to old, over oxidized sludge with a low F/M and high SRT
What is the result of the formula Ϭ r2 x Depth?

? Cubic feet
? Gallons
? Square feet
? Detention time
Cubic feet
Cubic feet is a three-dimensional measurement.
Ϭ r2 would be the calculation for surface area in sq. ft.
Ϭ r2 x Depth x 7.48 would equal gallons in a circular tank.
What is the main difference between SRT and MCRT?

? Influent CBOD5
? The RAS rate
? Total solids vs. volatile solids
? Detention time
Total solids vs. volatile solids
Most reference books use total solids to calculate SRT and volatile solids to calculate MCRT. The age determining formula used is not as important as being consistent in your sampling and calculation methods
What does the following formula represent?

Flow, gallons/day ÷ Surface Area, sq.ft.

? Weir overflow rate
? Solids loading rate
? Surface settling rate
? F/M ratio
Surface settling rate
This determines the number of gallons per day applied to each square foot of clarifier tank surface
Which RAS condition may indicate the need to increase the aeration process D.O.?

? High nitrates in the RAS
? Strong odors in the RAS
? Pin floc in the RAS
? Low solids concentration in the RAS
Strong odors in the RAS
Septic smelling RAS is typically the result of either low aeration D.O. or an RAS rate that is too low.
Typically, when an aeration tank is over-aerated, or overloaded (high F/M ⬦ low MLSS), what color will the foam be?

? Dark black
? Tan and greasy
? Stiff and white
? Orange
Stiff and white
Young sludge foam is most typically white and billowy.
Usually, as the MLSS gets older, the foam and scum get darker ... from brown to black
Which two categories best describe loading rates?

? Influent and hydraulic loading
? Hydraulic and effluent
? Organic and mixed liquor
? Hydraulic and organic
Hydraulic and organic
Hydraulic loading is based on the number of gallons that pass through a process; and organic loading is based on the number of pounds that pass through a process.
What does this formula best describe?

27,022 lbs/day ÷ 7,250 ppm x 8.34 lbs/gal

? Pounds of solids to waste
? Concentration of sludge to waste
? mgd of sludge to waste
? gpm of sludge to waste
mgd of sludge to waste
This is basically the "Q" formula.
Pounds to waste divided by concentration in ppm times 8.34.
Q formula answers are always expressed in mgd.
Which loading rate is associated with all of the following: tank volume and capacity (cubic feet and gal), detention time (hours), surface settling rate (gpd/ft2) and weir overflow rate (gpd/ft of weir length)?

? Organic
? Solids
These calculations all deals with gallons of flow entering a process unit, and not pounds loading.
Which is an aerobic process where certain groups of microorganisms convert Ammonia-N into Nitrite-N and then to Nitrate-N?

? Fermentation
? Anoxic
? Anaerobic
? Nitrification
Nitrosomonas convert NH3 to NO2 ⬦ and then Nitrobacter convert NO2 to NO3
What will microorganisms typically do when subjected to an excessive supply of food (CBOD5)?

? Grow and multiply
? Slow their growth process
? Die
? Nitrify
Grow and multiply
This is typical of healthy, active, heterotrophic microorganisms.
Which microorganisms are most responsible for stabilization of organic material?

? Rotifers
? Stalk Ciliates
? Bacteria
? Worms
Rotifers, stalked ciliates and worms are only indicators
Which growth phase typically produces the highest degree of cannibalism among the microorganisms?

? Log Growth
? High Rate
? Endogenous Respiration
? Declining Growth
Endogenous Respiration
This is far right on the growth curve ⬦ old sludge.
Which conditions will typically allow filamentous bacteria to grow and become dominant in activated sludge?

? Low D.O. and high F/M
? High D.O. and low F/M
? High D.O. and high F/M
? Low D.O. and low F/M
Low D.O. and low F/M
Filamentous bacteria can better compete for low food values at low D.O. ⬦ as compared to floc-forming bacteria.
Which bacterial group typically produces a higher sludge yield as a result of assimilation?

? Heterotrophic
? Autotrophic
? Nitrifiers
? Anaerobic
Carbon-eating bacteria (heterotrophic) typically generate a higher sludge yield as compared to ammonia-oxidizing bacteria (autotrophic).
Which type of bacteria can use oxygen either in a free, dissolved form or a combined form?

? Aerobic
? Anaerobic
? Facultative
? Fermenters
Facultative bacteria are heterotrophic, carbon-eating bacteria.
Electron microscopes are commonly used to observe living microorganisms.

? True
? False
Electron microscopes are typically used to observe microorganisms in the dead state.
Which microorganisms can typically ingest many types of small organic particles, but bacteria are their main food source?

? Amoebas
? Rotifers
? Stalked Ciliates
? Free Swimming Ciliates
Rotifers are typically indicative of stable activated sludge.
Which indicator organisms will be more dominant when the SRT is low and the sludge is young?

? Rotifers
? Stalk Ciliates
? Water Bears
? Free Swimming Ciliates
Free Swimming Ciliates
Rotifers and water bears indicate older sludge.
What may be the most probable cause for slow settling MLSS?

? High RAS rate
? Filamentous bacterial growth
? Balanced F/M ratio
? Low sludge blanket
Filamentous bacterial growth
Slow settling MLSS may be caused from an over-population of filamentous bacteria.
Also, high MLSS concentrations, with or without filamentous bacteria, may cause the MLSS to settle slow.
What is the typical adjustment that is necessary when the influent CBOD5 increases?

? Decreased WAS rate
? Decreased RAS rate
? Increased WAS rate
? Reduced sludge yield
Increased WAS rate
Increased CBOD5 usually means increased sludge production.
In order to maintain a constant MLSS concentration, it may take an increased rate of WAS.
Which condition is typically not the cause of high effluent ammonia?

? Low influent alkalinity
? High influent ammonia
? Low Aeration rate
? High Aeration D.O.
High Aeration D.O.
When the aeration D.O. is high, this usually results in very low effluent ammonia levels ... complete nitrification.
However, high aeration D.O.'s, may result in high nitrate values in the effluent ... reduced denitrification rate.
Which condition may cause biologically-bound phosphorus to be released in the secondary clarifier?

? High RAS rate
? Low SRT
? Low RAS rate
? High F/M ratio
Low RAS rate
Low RAS rates may create anoxic to fermentation conditions in the sludge blanket, which may result in the release of phosphorus from the sludge blanket into the clarifier effluent.
Increasing the RAS rate may improve this condition
What may be the most common cause of filamentous bulking in a secondary clarifier?

? Aeration D.O. too low
? SRT too low
? RAS rate too high
? Aeration D.O. too high
Aeration D.O. too low
Filamentous bulking is typically caused by low dissolved oxygen (between 0.4 to 0.8 ppm) and low food availability ... low F/M ratio
What may be the cause of septic odors?

? Aeration D.O. too high
? Low H2S values in the influent
? WAS rate too high
? Aeration D.O. too low
Aeration D.O. too low
Septicity is usually the result of inadequate aerobic conditions and the on-set of anaerobic decomposition
What color foam and scum is typically the result of old sludge?

? White
? Dark brown or black
? Light brown
? Green
Dark brown or black
Old, over-oxidized mixed liquor usually results in dark brown to black foam and scum.
Younger MLSS may have lighter colored foam and scum
What may cause CBOD5 in the effluent to be unacceptable high?

? Aeration rate too high
? SRT too high
? F/M ratio too low
? Aeration rate too low
Aeration rate too low
Under-aeration may cause CBOD5 to leave the aeration process and enter the clarifier effluent without being oxidized (consumed or converted).
Increasing the aeration rate usually resolves this problem
What may be the best adjustment to make if pin floc in the clarifier is increasing TSS in the effluent to unacceptable levels?

? Increase the SRT
? Decrease the F/M ratio
? Decrease the SRT
? Decrease the WAS rate
Decrease the SRT
Pin floc is typically the result of old sludge with a high SRT and a low F/M ratio.
Increasing the WAS rate, which will decrease the SRT and increase the F/M ratio, is the normal process adjustment to reduce the pin floc condition.
What typically happens to the process SRT when the WAS rate is increased?

? SRT decreases
? F/M ratio decreases
? SRT increases
? SRT remains the same
SRT decreases
As the WAS rate is increased, the MLSS inventory is lowered, and the process SRT is reduced.
Which adjustment will normally improve denitrification in a conventional aeration tank?

? Increase the air supply
? Increase the D.O.
? Decrease the D.O.
? Shut off the RAS
Decrease the D.O
Denitrification is an anoxic reaction and reducing the D.O. typically improves the denitrification rate.
Which best describes the nitrification cycle?

? NO3 is converted to NH3
? NH3 is converted to NO2 and then to NO3
? NH3 is converted to NO3 and then to NO2
? NO2 is converted to NH3 and then to NO3
NH3 is converted to NO2 and then to NO3
Nitrification is an aerobic process where autotrophic bacteria convert ammonia to nitrates.
It takes about 4.6 pounds of oxygen to convert one pound of ammonia.
Given the “Fate of Phosphorus” profile, why does TP reduce through the 1st anoxic zone?

? Phosphorus is still being released
? CBOD5 uptake through denitrification
? Low aerobic conditions create Luxury P Uptake
? Nitrif
CBOD5 uptake through denitrification
As the denitrification reaction in the anoxic zone is consuming CBOD5, the phosphorus bugs are beginning to absorb P.
Which group of bacteria are responsible for converting nitrite to nitrate?

? Facultative
? Nitrosomonas
? Nitrobacter
? Heterotrophic
Nitrobacter are the 2nd group of autotrophic bacteria in the nitrification cycle.
They are responsible for the conversion of the unstable nitrite to the more stable nitrate.
Given the following data, calculate the lbs of alkalinity required for nitrification:

Flow = 26.5 mgd
Inf TKN = 42 mg/L
Eff NH3 = 0.75 mg/L
90% TKN converted to NH3
7.14 lbs Alkalinity consumed for each lb of NH
58,465 lbs
Lbs/day ammonia converted = 26.5 mgd x ((42 mg/L x 0.9) - 0.75 mg/L) x 8.34 = 8,188 lbs lbs/day ammonia converted
Lbs alkalinity required = 8,188 lbs ammonia converted x 7.14 lbs alkalinity per lb ammonia
= 58,465 lbs alkalinity
Notes: 0.9 is 90% of the influent TKN ⬦ ammonia to be nitrified ... 0.75 mg/L effluent ammonia is subtracted from the total lbs of ammonia nitrified

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