CVEN 5534

Spring 2008

ASSIGNMENT 4: Due Thursday, Feb. 28

1. Develop formulas for the minimum min for COD oxidizing

biomass and for nitrifying biomass using the parameters given

in the example.

2. Calculate these values and compare with the spreadsheet.

3. Specify the CSTR volume and solids retention time () you

would choose for this example and justify your answer.

4. Show the effect of decreasing the YH to 0.4 on min with

nitrification.

5. Calculate the viable heterotrophic and nitrifying biomass at

the design  and .

6. What would be the advantages of operating this CSTR-

biomass recycle process at lower than maximum oxygen supply

rate?

7. Evaluate the sensitivity of the model predictions for COD and

ammonia removal and minimum hydraulic residence time

(min) to the variation in the decay coefficient, b, and the

maximum specific growth rates for heterotrophic and

autotrophic bacteria, . The range of variation in the

growth and decay parameters should be ± 50%. Show the

effects graphically: e.g. effluent COD vs b, XT vs , etc.