ANAEROBIC BIODEGRADATION OF TOLUENE IN A PLUG- FLOW REACTOR

ABSTRACT This paper presents the application of a continuous-flow, mesophilic (35°C), plug-flow digester to cometabolic degradation of toluene by an anaerobic microbial consortium in the presence of conventional pollutants serving as the major carbon and energy sources. In contrast to conventional practice, digester contents were not mixed. Reactor effluents were recirculated to the influent end at a rate of 20 vol. percent of the influent flow rate. The anaerobic digester was charged with 50 mg/l of toluene. The total COD (chemical oxygen demand) concentration of the mixed, non-hazardous carbon sources was 11,000 mg/l. Experimental results showed that anaerobic digestion occurring in a plug-flow reactor can simultaneously stabilize and detoxify conventional and hazardous wastes with the production of a methane-rich (up to 80 mol % methane) fuel gas. The observed gas yield of 0.36 ± 0.01 SCM/kg VS added was higher than that of conventional, complete-mix digesters under similar operating conditions of hydraulic retention time (HRT) and organic loading rate (OLR). Toluene did not inhibit anaerobic biogasification of non-hazardous substrates. A toluene degradation efficiency of 95 % and a total COD reduction of 96 % were observed at an HRT of 13 days and an OLR of 0.81 kgCOD/m3-day. Digester effluents contained about 2 mg/l of toluene under these operating conditions. Toluene released to the reactor head ga