Effects of carbonate and phosphate concentrations on hydrogen production using anaerobic sewage sludge microflora

Abstract

Anaerobic sewage sludge acclimated with sucrose in a completely stirred tank reactor operating at 35°C was used as the seed (dominated by Clostridia species) in a batch experiment to investigate the concentration effects of carbonate and phosphate on biological hydrogen production. The Taguchi orthogonal array was used in the experimental design and a confirmation experiment was conducted. Experimental results indicated that the hydrogen production ability of the anaerobic microflora in sewage sludge was affected by NH 4HCO 3, Na 2HPO 4 and Na 2CO 3 with Na 2HPO 4 being the most significant supplement. Na 2HPO 4 affected the hydrogen production in a concentration-dependent way with 600 mg/l the optimal concentration. The hydrogen production rate was 1.9 times enhanced, compared with an acidogenic nutrient formulation (Proc. Soc. Civ. Engrs. 325 (1982) 61), when a proper carbonate and phosphate concentration formulation was used. The enhancement was due to a shortening of the microflora lag-time. Based on the enhancement abilities on hydrogen content and hydrogen production rate, adding phosphate instead of carbonate as a buffering capacity supplement might be a useful strategy for optimal hydrogen production operations with anaerobic sewage cultures.