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21 Cards in this Set
- Front
- Back
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What are the three controls an operator has over the activated sludge process? |
1) Air flow rate 2) Wasting rate 3) RAS rate |
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What is the most important control measure an operator has in activated sludge? |
MCRT |
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Calculate MCRT |
lbs in system/lbs leaving the system |
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Equation for MCRT and Growth Rate |
MCRT = 1/Growth Rate. I.e., the MCRT is the reciprocal of the growth rate. |
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What range should the DO be kept at in the aeration basin? |
1-3 mg/L |
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How many cubic feet of air are needed per pound of BOD introduced to the aeration basin? |
1000 |
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Of growth rate, number of microorganisms, and mass of microorganisms, what do operators ultimately control? |
The growth rate |
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What do microorganisms in the aeration basin use for maintenance and growth? |
Organic Carbon |
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What three factors determine the mass of the microorganisms in the aeration basin? |
1) Mass of BOD influent to the system 2) The growth rate being maintained (MCRT) 3) Temp of wastewater |
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What three approaches are commonly in practice to to set the WAS rate? |
1) Maintaining a constant MLSS/MLVSS (not advised, this is a response variable) 2) Maintaining a constant MCRT 3) Maintaining a constant F:M ratio (not advised) |
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What is the typical MCRT for package plants and oxidation ditches? |
20-30 days |
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What four mass measurements are used in the MCRT calculation? |
1) lbs MLSS in aeration basin 2) lbs MLSS in Secondary Clarifiers 3) lbs per day of TSS unintentionally lost in the effluent 4) lbs per day intentionally lost in the WAS |
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What assumption is needed to calculate lbs in the system for the sake of the exams? |
MLSS aeration = MLSS Secondary Clarifier |
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Official units for F/M ratio |
Pounds of BOD applied to aeration basin / Pounds of MLVSS in aeration basin |
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'Low F:M conditions' are synonymous with…. |
'Long MCRT' |
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Which is used for what calc, MLSS and MLVSS for MCRT and F:M |
MLSS - MCRT MLVSS - F:M |
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What volumes are considered for which calc, Aeration Basin volume and Secondary Clarifier Volume, for MCRT and F:M |
MCRT - Both F:M - Only Aeration Basin volume |
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The sole purpose of RAS |
To keep the biomass in the aeration basin and out of the secondary clarifiers |
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What two considerations are appropriate for determining the % RAS flow rate (compared to the influent) |
MLSS concentration and Settleability |
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Typical RAS flow rate % |
25-50% Conventional 75-150% Extended aeration
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What is the optimum RAS flow rate? |
The lowest possible that does not result in a significant sludge blanket |
