General method for determining anaerobic biodegradation potential

Abstract

A simple, generalized method was refined and validated to test whether an organic chemical was susceptible to anaerobic degradation to CH4 + CO2. The method used digested sewage sludge diluted to 10% and incubated anaerobically in 160-ml serum bottles with 50 micrograms of C per ml of test chemical. Biodegradation was determined by the net increase in gas pressure in bottles with test chemicals over the pressure in nonamended sludge bottles. Gas production was measured by gas chromatography and by a pressure transducer. The latter method is recommended because of its speed, accuracy, and low cost. Sewage sludge from municipal digesters with 15- to 30-day retention times was found to be suitable. The sludge could be stored anaerobically at 4 degrees C for up to 4 weeks with satisfactory test results. p-Cresol, phthalic acid, and ethanol are suggested as reference chemicals to confirm sludge activity and method reliability. A revised anaerobic salts medium was developed which minimizes problems of a biological gas production (CO2), avoids precipitation, and meets the requirements of the anaerobic microbiota. When greater than 75% of the theoretical gas production was observed, the chemical was judged to be degradable, and when 30 to 75% of the expected gas was produced, it was termed partially degradable. This method has been tested on more than 100 chemicals of various physical properties and found to reproducibly determine anaerobic biodegradation potential. Of the chemicals tested, 46 were found to be anaerobically degraded. Sludges from nine different municipal treatment plants were surveyed for their ability to degrade nine chemicals which differed in susceptibility to degradation.(ABSTRACT TRUNCATED AT 250 WORDS)