compounds with a total soluble COD of 400 mg/L. The wastewater contained no particulate matter. The studies were run in lab scale bioreactors that had a volume of 6.0 L. The llow rate was maintained at a constant rate of l.O L/hr and the SRT was maintained at the desired values by wasting excess biomass directly from the reactors. The wastage rate was corrected for the loss of biomass in the effluent. Data collected from the bioreactors are shown in Table E8.2. In addition, biomass was removed from the bioreactor with an SRT of 96 hr, doubled in concentration by settling, and placed in a batch reactor to allow measurement of the OUR over time for estimation of b„. The data from this test are shown in Table E8.3. Using the information provided, estimate the values of the parameters bu and YM. Assume that fn has a value of 0.20.

a. The first task is to determine bM from the batch data given in Table E8.3. This is done by plotting the natural log of the OUR versus time. The resulting plot is shown in Figure E8.5. The value of b,, is equivalent to the slope of the line, which is 0.007 hr '.

b. Once bM has been evaluated it is possible to estimate Y,, from Eq. 8.17, provided a value is available for f,>. No data are available on the active fraction of the biomass, so it is necessary to assume a value for f,,. The risk

Table E8.3 Data Collected During a Batch Aeration Test for the Determination of bM


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