BIOAUGMENTATION OF ANAEROBIC DIGESTION WITH A COMMERCIAL BIOCATALYTIC ADDITION

Abstract

A commercial biocatalytic addition that was adopted for use in a local wastewater treatment plant was studied in this project. The bacterial composition of this biocatalytic addition was determined. Its action on anaerobic digestion of wastewater sludges rich in free fatty acids and its mode of action were also studied. A total of 9 pure cultures were isolated from this biocatalytic addition, all of which could be classified under the broad grouping of acid formers in anaerobic digestion. No methane formers were found. The biocatalytic addition was found to primarily degrade complex organics into simple volatile acids. In a batch reaction, acid production was eminent, with high levels of increase in enzyme activities. No methane production was detected. The biocatalytic addition did not improve the performance of anaerobic digestion at free fatty acids contents of 0, 5000 and 10000 mg/l, under steady states at solids retention time of 20 days. The biocatalytic addition also did not give any improvement at varying levels of biocatalyst dosage. The solids retention time was then 10 days and the free fatty acids content was 10000 mg/I. It was concluded that the biocatalytic addition is a mixture of bacteria common in soil and water. While it speeds up the hydrolysis and acid fermentation of complex organics, it does not carry the reaction to its completion. It is thus not able to improve the efficiency of anaerobic digestion of wastewater sludges with high levels of oil and grease.