8.2.6 Estimation of k.
In situations in which the organic compounds in the wastewater are relatively easy to degrade, the soluble biodegradable COD in the effluent from the CSTRs is likely to be small relative to the half-saturation coefficient. This makes it difficult to obtain independent estimates of |iM and Ks. In that situation it is better to use the first order approximation of the Monod equation to express the biodégradation kinetics of the wastewater constituents. It was given in Eq. 5.41:
In that case, a plot of Ss versus (l/("\ + b„) will yield a straight line that passes through the origin. Its slope will be l/(Y„-kc) and can be determined from linear least squares analysis. Because the value of Y,, is already known, the slope can be used to determine the value of k,., the mean reaction rate coefficient.
A treatability study was performed on an industrial wastewater using CSTRs with biomass recycle. The wastewater contained a complex mixture of soluble organic compounds with a total soluble COD of 350 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 flow rate was maintained at a constant rate of 1.0 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. Batch studies with biomass removed from one of the reactors revealed
Table E8.1 Data Collected During a Treatability Study with a Soluble Industrial Wastewater
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