SUBSTRATE INTERACTION DURING AEROBIC BIODEGRADATION OF CREOSOTE-RELATED COMPOUNDS IN COLUMNS OF SANDY AQUIFER MATERIAL

A column study was initiated to study the effect of phenanthrene, fluo rene, and p-cresol on the aerobic biodegradation of carbazole in colum ns of sandy aquifer material. Biodegradation of the contaminant mixtur e was sequential in space with p-cresol being preferentially degraded, followed by phenanthrene, then the other compounds, Both p-cresol and phenanthrene were completely biotransformed to non-detectable levels during passage through the 46 cm sand column but some carbazole and fl uorene persisted throughout the approximately 3 month experiments, Inf luent p-cresol (10 000 ppb) was the only compound that affected adapta tion of the microbial community to carbazole biodegradation, but its e ffect was of little practical importance, amounting to a 4.5 day diffe rence in carbazole breakthrough. However, when influent p-cresol was a t high levels (70 000 ppb), biotransformation of the other co-substrat es in the mixture never ensued because p-cresol caused complete dissol ved oxygen depletion. Conversely, influent p-cresol ultimately enhance d biotransformation of the other co-substrates in the mixture when pre sent at a concentration (10 000 ppb) that did not deplete all availabl e oxygen. The concentrations of the other, more recalcitrant compounds , ranging between 33 and 238 ppb, were probably too low to support bac terial growth so that slow, limited biotransformation resulted, althou gh addition of an auxiliary substrate (i.e. the p-cresol) stimulated t heir biotransformation. Under quasi-steady-state conditions, the prese nce of phenanthrene in the influent inhibited fluorene biotransformati on and possibly carbazole biotransformation. Results of the present st udy demonstrated also that interactions identified in static batch mic rocosms and in a hydrodynamic saturated column system can differ. (C) 1998 Elsevier Science B.V.