Anaerobic digestion of pig manure mixed with sewage sludge

This experiment explored the possibility of treating pig manure plus sewage sludge by anaerobic digestion, using batch fermentation at 37°C. The results indicated that the digested materials contained a lower level of putrescible matter when compared to the raw materials. Co-digestion of pig manure and sewage sludge at the ratio of 2:1 seemed to give the best results in terms of reducing the organic load and yielding a higher volume of methane. The experiment should be repeated in digestion tanks of a sewage treatment plant, especially for treating pig manure which has been recognized as the major source of water pollution in Hong Kong.