The effect of calcium on the anaerobic digestion treating swine wastewater

Abstract

A series of experiments with 0, 1, 3,5, and 7 g Ca2+/l using calcium chloride were performed to evaluate the effect of various calcium concentrations on anaerobic digestion of swine wastewater. The addition of 3 g/l gave the best performance. On the other hand, the calcium concentrations of 5-7 g/l had an inhibitory effect on anaerobiosis. The lag phase durations expected in biogas production were 28-31 days with the addition of 0-3 g/l of calcium, and 43-52 days for calcium concentrations of 5 g/l or more. The concentrations of total volatile fatty acids decreased to less than 100 mg/l with calcium concentrations of 3-7 g/l. On the other hand, propionate and i-valerate concentrations remained over 4 and 0.8 g/l, respectively, when 1 g/l or less of calcium was added. (c) 2006 Elsevier B.V. All rights reserved.