USE OF ANAEROBIC HYBRID REACTORS FOR TREATMENT OF SYNTHETIC PHARMACEUTICAL WASTEWATERS CONTAINING ORGANIC-SOLVENTS

The performance of anaerobic hybrid reactors treating an organic solve nt-containing synthetic pharmaceutical wastewater was evaluated under various wastewater volumetric loading rates and influent compositional changes. The biodegradation, toxicity and treatability of the target C-3 and C-4 solvents, tert-butanol isopropanol, isobutanol sec-butanol and ethyl acetate, were examined. At a hydraulic retention time (HRT) of 2 days and volumetric loading rates ranging from 3.5 to 4.5 kg COD m(-3) day(-1), the reactors achieved total and soluble COD removal ef ficiencies of 97-99% in less than five times the HRT. These removal ra tes were achieved following the introduction of target solvents not pr eviously supplied to the reactors. However, inadequate removal of tert -butanol resulted in a decrease in the soluble COD removal efficiency to 58%. Bacterial enrichments from the reactor biomass using tert-buta nol as the sole substrate proved unsuccessful, confirming that tert-bu tanol is poorly degradable anaerobically. Inclusion of a trace metal c ocktail in the feed did not affect steady-state reactor performance, b ut was beneficial during changes in the influent composition. After 40 5 days of operation, the matrix-associated biomass contributed only a minor fraction (2-4%) of the total biomass present in both reactors. O n takedown, the retained biomass present in the matrix-free section of both reactors was found to be granular in nature, despite the omissio n of trace elements from the influent to one of the AHRs. The specific methanogenic activity profile of the granular sludge from the trace e lement limited AHR was, however, significantly lower (alpha = 0.05) th an that of the reference AHR.