ANAEROBIC DEGRADATION OF BENZOATE

Abstract

Anaerobic biodegradability of a wastewater is assessed by its biochemical methane potential (BMP). Degradation of phenol in single phase is presented in the literature. Considering toxic nature of phenol it is worthwhile to explore the possibility of treating phenol in two phases. Formation of benzoate has been shown to be rate limiting step (slow process) in a sequential biotransformation of phenol to benzoate. Keeping this in view, response of phenol and benzoate to different anaerobic inocula has been investigated in batch reactors (Oxitop bottles with pressure sensors). Experiments were carried out in two phases. In Phase I, the anaerobic-biodegradability-of-phenol-and-benzoate were evaluated using (a) washed granular acclimatized sludge and (b) flocculent unacclimatized sludge. The toxicity of benzoate has been investigated in. Phase II using granular acclimatized sludge for varying concentration of benzoate COD from 2495.6-11,684 mg/L. Data collected in Phase I and II has been analyzed to evaluate the rate of phenol degradability in terms of methane generation rate constant (k, d-1), conversion of phenol and benzoate fed to ultimate CH4-COD (BMPU, gb), and sludge activity [mL CH4 or g CH4-COD formed /g VSS (sludge)]. In this study it has been found that the temporal cumulative methane generation follows either logistic S-curve or logarithmic curve. In Phase I, it was found that benzoate easily degradable as compared to the phenol and in the phase-II, found that the toxicity increases with an increase in the COD i.e. the rate of degradation decreases with an increase in COD. In phase II, in general, rate constant, k was found to decrease from 0.793 to 0.106 and ultimate BMP from 84% to 60%.