Fatty acids profile during anaerobic digestion of night soil-effect of temperature, calcium carbonate and selectively-enriched inoculum

Abstract

Anaerobic biodegradation of night soil was carried out at 5-30°C with 1.8-10.62 per cent volatile solids (VS). Biogas production increased with the temperature and VS up to 6.2 per cent. Further increase in VS caused higher volatile fatty acids (VFA) accumulation resulting in decreased gas production. Acetate and propionate accounted for 62-83 per cent of total VFA. Butyrate to isobutyrate ratio increased with VS. Calcium Carbonate promoted VS degradation, biogas production and VFA degradation. The increased methanogenic and decreased sulphate-reducing bacteria caused proportional changes in CH4 and H2S gases. Enrichment with H2 oxidising methanogenic consortium is beneficial by enhancing VFA utilisation by two to three fold.