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20 Cards in this Set

  • Front
  • Back
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 aeration mode is intended to dilute high demand influent loadings?

? Plug flow
? Step feed
? Complete mix
? Contact stabilization
Step feed combines influent and RAS and introduces it across the length of the tank.
This dilutes the demand for oxygen throughout the tank.
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 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 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 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
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.
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
The beginning of the aeration tank usually has the highest concentration of CBOD5 and ammonia and the most potentially active microorganisms.
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.
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
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 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.
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 liquor.
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.
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.
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
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 growthto 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 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.
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
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 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.