Avoiding digester upset.

The acetate uptake bioassay (AUB) is a predictive measure for determining the stability of anaerobic digesters, but its use is rare due to the limited availability of gas chromatography equipment at wastewater treatment facilities. A water displacement system was compared and evaluated as an alternative to gas chromatography analysis for conducting the AUB. Results indicated that methane generation rates measured by the two methods were statistically the same. Precision of the method varied by less than 5%. Accuracy was quantified by measuring near stoichiometric volumes of carbon dioxide gas production from abiotic tests using sodium carbonate and hydrochloric acid. The method detection limit (MDL) was 0.6 mL. The effective use of a water displacement system as a surrogate for gas chromatography analysis could make the adoption of the AUB for predicting digester stability a practical option for treatment facilities.