PENTACHLOROPHENOL BIODEGRADATION KINETICS OF AN OLIGOTROPHIC FLUIDIZED-BED ENRICHMENT CULTURE

A fluidized-bed reactor (FBR) was used to enrich an aerobic chlorophen ol-degrading microbial culture. Long-term continuous-flow operation wi th low effluent concentrations selected oligotrophic microorganisms pr oducing good-quality effluent for pentachlorophenol(PCP)-contaminated water. PCP biodegradation kinetics was studied using this FBR enrichme nt culture. The results from FBR batch experiments were modeled using a modified Haldane equation, which resulted in the following kinetic c onstants: q(max) = 0.41 mg PCP mg protein(-1) day(-1), K-s = 16 mu g 1 (-1), K-i = 5.3 mg 1(-1), and n = 3.5. These results show that the cul ture has a high affinity for PCP but is also inhibited by relatively l ow PCP concentrations (above 1.1 mg PCP 1(-1)). This enrichment cultur e was maintained over 1 year of continuous-flow operation with PCP as the sole source of carbon and energy. During continuous-flow operation , effluent concentrations below 2 mu g 1(-1) were achieved at 268 min hydraulic retention time (t(HR)) and 2.5 mg PCP 1(-1) feed concentrati on. An increase in loading rate by decreasing t(HR) did not significan tly deteriorate the effluent quality until a t(HR) decrease from 30 mi n to 21 min resulted in process failure. Recovery from process failure was slow. Decreasing the feed PCP concentration and increasing t(HR) resulted in an improved process recovery.