IMPACT OF CHLOROANILINES ON HYDROGENOTROPHIC METHANOGENESIS IN ETHANOL-ENRICHED CULTURES

The impact of toxic organic chemicals on the kinetics of hydrogen conv ersion in ethanol-enriched cultures has been investigated. The study f irst involved an assessment of the kinetics of gaseous hydrogen transf ormation in a hydrogen-enriched culture. Tests to quantify the distrib ution of biomass in an ethanol-enriched culture indicated that hydroge notropic methanogens made up 25.4% of the total biomass. Various amoun ts of chlorinated anilines were then added to ethanol-enriched test cu ltures to determine their impact on the hydrogen conversion reaction. Test results indicated that hydrogen conversion was mass-transfer limi ted from the gas phase but not from solution. While chlorinated anilin es had a major adverse impact on acetogenic conversion of ethanol to h ydrogen, the associated hydrogenotrophic methanogenesis reaction was a ffected to lesser extent by the toxicants. Tests with 3-chlorophenol s howed similar inhibition of acetogenesis and acetoclastic methanogenes is but not hydrogenotrophic methanogenesis. The principal significance in this study is thought to lie in the use of specific hydrogenotroph ic biomass for assessing the kinetics of hydrogen conversion and in th e observation that the kinetics of hydrogenotrophic methanogenesis was not adversely affected by chlorinated anilines and chlorinated phenol s. The principal application lies in the observation that gas-phase hy drogen may not be a good measure of the impact of toxic organic chemic als on anaerobic digestion processes.