Effect of varying volumes of anaerobic microbial inoculum on biodegradation and biogas production from black water

Unfettered discharge of untreated black water is one of the raging environmental issues which needs to be addressed especially in many developing and third-world countries. Black water is rich in organic compounds, elements such as nitrogen and phosphorous, and harmful faecal coliforms which makes it a major threat to the environment. The present study focuses on the use of an inhouse anaerobic microbial inoculum for the treatment of black water with an emphasis on decentralized treatment systems. The effects of varying volumes of inoculum (5 %, 10 %, 20 % & 30 %) for the treatment of black water was studied. Various parameters such as pH, total solids (TS), volatile solids (VS), chemical oxygen demand (COD) and biogas production were recorded. 10 % inoculum yielded the maximum amount of biogas. The biogas volume varied from 1046 mL–1180 mL depending on the experiments carried out using either fresh inoculum or acclimatized old inoculum. The inoculum could also be reused for sustained biodegradation and biogas production process which makes its use economic and apt as inoculum for reactors used in decentralized treatment processes. An attempt was also made in this work to reduce the input COD imparted via the inoculum itself by letting the larger and heavier solids to settle. Nevertheless, it was observed that the best working inoculum was the 10 % whole inoculum in terms of biogas production and COD removal.