Impact of chloroanilines on hydrogenotrophic methanogenesis in ethanol-enriched cultures

The impact of toxic organic chemicals on the kinetics of hydrogen conversion in ethanol-enriched cultures has been investigated. The study first involved an assessment of the kinetics of gaseous hydrogen transformation in a hydrogen-enriched culture. Tests to quantify the distribution of biomass in an ethanol-enriched culture indicated that hydrogenotropic methanogens made up 25.4% of the total biomass. Various amounts of chlorinated anilines were then added to ethanol-enriched test cultures to determine their impact on the hydrogen conversion reaction. Test results indicated that hydrogen conversion was mass-transfer limited from the gas phase but not from solution. While chlorinated anilines had a major adverse impact on acetogenic conversion of ethanol to hydrogen, the associated hydrogenotrophic methanogenesis reaction was affected to lesser extent by the toxicants. Tests with 3-chlorophenol showed similar inhibition of acetogenesis and acetoclastic methanogenesis but not hydrogenotrophic methanogenesis. The principal significance in this study is thought to lie in the use of specific hydrogenotrophic biomass for assessing the kinetics of hydrogen conversion and in the observation that the kinetics of hydrogenotrophic methanogenesis was not adversely affected by chlorinated anilines and chlorinated phenols. The principal application lies in the observation that gas-phase hydrogen may not be a good measure of the impact of toxic organic chemicals on anaerobic digestion processes.