Evaluation of laboratory-made sludge for an anaerobic biodegradability test and its use for assessment of 13 chemicals

Laboratory-made sludge for a biogas based anaerobic biodegradability test was prepared as an alternative for digested sludge from wastewater treatment plants (WWTPs). Biodegradation activities and background gas productions of digested sludge from various WWTPs were found to vary significantly depending on the source, which adversely affected test reliability. Subsequently, test conditions such as sludge concentration and sludge washing were examined with the laboratory-made sludge and a sludge concentration of 1.0 g-SS/L without washing was determined to be most suitable. Under these conditions, biodegradability tests were conducted for 13 select chemicals and their relative toxicities to methanogenic bacteria were evaluated. The results of biodegradability tests showed that chemicals with -OH and -CH2OH radicals were readily biodegraded and those with -Cl, -NO2, -NH2, -SO3H and -CH3 had inhibited degradation responses m-nitriphenol and 2,4,6-trichlorophenol were highly toxic to methanogenic bacteria, with m-nitrophenol completely inhibiting methane fermentation as low as 20 mg/L.