Degradation characteristics of a propionate enriched culture at slightly acidic conditions

To clarify the effects of pH on propionate degradation in an anaerobic system, the degradation characteristics of a propionate enriched culture at slightly acidic conditions were investigated. Under the biomass of 0.22g MLVSS/L and initial propionate of 1000mg/L conditions, propionate was rapidly oxidized at pH7.0 (control) and propionate removal achieved 98.5% after 6days cultivation. pH decrease, from 7.0 to 6.5 and 6.0, resulted in propionate removal rate was decreased instantaneously. But propionate degradation rate was recovered to the value at pH 7.0 after 2~3 days adaptation. Propionate removal at pH 6.5 and pH 6.0 were reached above 97% after 8 days and 9 days cultivation, respectively. Propionate was hardly decomposed at pH 5.5 during the whole cultivation. During the whole experiment, no hydrogen was detected and acetate was transient accumulation in the early culture. These results indicated methanogens were more acid resistance than propionate-oxidizing bacteria.