A FIXED-FILM BIOASSAY FOR THE DETECTION OF MICROPOLLUTANTS TOXIC TO ANAEROBIC SLUDGES

Micropollutants in waste water streams can be a serious problem for the anaerobic digestion process. A short-term acute bioassay system is described for testing the effects of new and potentially toxic compounds on anaerobic digestion processes. Change in methanogenic activity was used as the monitored process parameter and the performance of intoxicated inocula was compared to activity prior to adding test compounds and to the activity of a parallel control assay. The performance of the bioassay was tested with chlorinated solvents and heavy metals. Trichloroethane caused a 50% reduction in methanogenic activity at 7 mg/l assay. The performance of suspended and fixed biomass assays were compared; the suspended growth was found to be five times more sensitive to trichloroethane. There was no clear inhibition with the heavy metals even at the highest concentration used (up to 750 mg Cu/l). The duration of assay was found to be an important parameter in the evaluation of anaerobic toxicity.