INHIBITION OF METHANOGENIC ACTIVITY OF STARCH-DEGRADING GRANULES BY AROMATIC POLLUTANTS

The effects of nine common aromatic pollutants from chemical industry on the bioactivity of anaerobic granules were examined. The granules w ere obtained from an upflow anaerobic sludge blanket (UASB) reactor tr eating wastewater containing colloidal starch. The specific methanogen ic activities (SMA) of granules were measured at 37 degrees C in serum vials using 3000 mg/l of colloidal starch as substrate, plus individu al pollutants at various concentrations. The toxicity was expressed by the IR50 and IC50 values, i.e. the toxicant/biomass ratio and concent ration at which levels the granules exhibited only 50% of their origin al bioactivities. Results showed that in general the granules exhibite d mild resistance to toxicity of aromatic pollutants, probably due to the granules' layered microstructure. The toxicities, which were depen dent on the nature of chemical functional group, of the aromatic pollu tants were in the following descending order: cresols > phenol > hydro xyphenols/phthalate > benzoate. There was only marginal difference bet ween the toxicity of the steric isomers. For the seven phenolic pollut ants, the more hydrophobic the functional group the higher the toxicit y. The granules' resistance to toxicity suggested the plausibility of anaerobic treatment of wastewater from the chemical industry. (C) 1997 IAWQ. Published by Elsevier Science Ltd.