DEHALOGENATION OF 2-CHLOROPHENOL (2-CP) IN ANAEROBIC BATCH CULTURES

The effects of seed materials from: anaerobically digested sewage slud ge; sediment from a bleached kraft mill (BKM) aerated lagoon and an an aerobic bioreactor biomass treating BKM wastewater were investigated a s to their potential for dehalogenation of 0.38 mM 2-chlorophenol. In batch cultures using a mineral medium containing 0.1% yeast extract un der 20% CO2 + 80% N-2 or 20% CO2 + 80% H-2 atmosphere, dehalogenation was observed after extensive lag periods lasting from 97 to 250 days. Methane was detected in the head-space. Phenol was identified as an in termediate which further degraded via the benzoate pathway. The dehalo genation rates increased significantly in all cultures after re-spikin g with 2-CP and yeast extract medium. Cultures with digested sewage sl udge incubated under CO2/N-2 head-space exhibited better dehalogenatio n rates of 2-CP compared to either the lagoon sediment or the bioreact or biomass. Higher dehalogenation rates were also observed over CO2/N- 2 head-space compared to CO2/H-2 head-space for digested sludge. Diges ted sludge which was adapted to 2-CP over a one year period converted 0.38 mM 2-CP to phenol immediately. Degradation of 2-CP with various d ilutions of adapted sludge indicated that dehalogenation activity did not increase linearly with biomass concentrations. The effect of four different organic electron donors on the dehalogenation of 2-CP by ada pted sludge revealed that 0.1% yeast extract was preferred by the cons ortium compared to 10 mM each of acetate, propionate or ethanol.