Biodegradation of multicomponent hazardous substrates
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This research evaluated kinetic parameters for a pulse-fed batch reactor that contains a multicomponent substrate media. Glucose, phenol, and pentachlorophenol (PCP) were chosen as the carbon sources because these substrates are very common constituents in industrial waste facilities that have petrochemical waste as the primary influent. A mixture of these three constituents represents a non-inhibitory substrate (glucose), a somewhat inhibitory substrate (phenol), and a very inhibitory substrate (PCP). Two techniques were used to obtain kinetic coefficients. Long-term kinetic studies in the batch reactors were used to evaluate cell growth and substrate utilization which also yielded information on the pollutant's total residence time in the reactor. From these experiments glucose removal is zero-order with respect to substrate concentration whose biodegradation follows typical Monod kinetics. After significant removal of glucose, phenol removal was initiated followed by pentachlorophenol removal. The initial rate method eliminated any possible lag phase that may have occurred in the long-term studies and allowed extrapolation of kinetic coefficients for cell growth and substrate utilization over short duration batch experiments. This method found the maximum specific growth rate (max) for glucose to be 0.45 h-1. Phenol degradation follows Monod kinetics in the non-inhibitory range (< 80 mg/l) with a max of 0.56 h-1, but PCP is very inhibitory with max = 0.03 h-1. When glucose and phenol are present and phenol concentration lies in a non-inhibitory range, Monod kinetics are exhibited. However, when glucose and phenol are present and phenol is in an inhibitory range, substrate inhibition (Haldane) kinetics are observed.
