Using a Bench Scale Test to Evaluate Anaerobic Digesters Stability and Capacity

Limited process information is available to describe the stability and capacity of anaerobic digesters at the Clean Water Services (CWS) facilities. To supplement this information, a bioassay has been implemented to monitor the digesters operated at the Durham and Rock Creek facilities. Weekly bioassays have been conducted over the past two years. The results have allowed us to evaluate the responses of the bioassay indicators to usual operational conditions, such as changes to loadings from fats, oils and grease addition, digester startup after cleaning, and mechanical difficulties. The indicators show a response to changes to loading and detention time and the type of feed that could help understand the risk of failure, and help distinguish mechanical from biological causes of foaming events.