A METHOD FOR SCREENING THE POTENTIAL TOXICITY OF ORGANIC-CHEMICALS TOMETHANOGENIC GAS-PRODUCTION

The objective of this study was to examine a simple anaerobic gas prod uction test for screening the toxicity of organic chemicals to anaerob ic metabolism. Inhibition of anaerobic digestion can pose a problem in sludge treatment systems as it may limit the biodegradation of hazard ous pollutants. The method used was based on a single measurement of t he headspace pressures in closed bottles containing inoculated medium and serial dilutions of the test chemicals. Under the applied methanog enic conditions, the anaerobic gas production was particularly sensiti ve to surfactants and Cl and NO2 substituted phenols. E.g., the EC50 v alues for the surfactants alkyl dimethylbenzylammonium chloride and so dium alkyl ethersulfate were 6.7 and 11 mg/l. Two of the surfactants a nd two of the phenols were also examined in the Microtox bioassay and in the growth inhibition test with Pseudomonas putida as these tests a re commonly used for screening the toxicity of chemicals. The anaerobi c gas production test was considerably less sensitive to toxic chemica ls than the Microtox bioassay. However, for the surfactants, the anaer obic tests gave lower effect concentrations than obtained in the tests with P. putida. Screening the toxicity of chemicals to anaerobic proc esses may predict the potential effects of pulse loadings to anaerobic digesters. Furthermore, knowledge about inhibitory concentrations may be very useful prior to anaerobic biodegradability testing. Copyright (C) 1996 IAWQ.