Enhancement in the treatment efficiency and conversion to energy of dairy wastewaters by augmenting CST Reactors with simple biofilm support systems

Dairy wastewaters are rich in organic carbon and nutrients. When disposed w ithout proper treatment they cause severe pollution of water and land. but if treated by anaerobic fermentation such wastewaters can yield useful dean energy in the form of methane The systems commonly used for such fermentat ion throughout the world are Continuously Stirred Tank Reactors (CSTRs). We describe attempts to upgrade CSTR performance by incorporating biofilm sup port systems (BSSs) within the existing reactors. The focus of the work has been to find inexpensive and easy-to-install BSS which could significantly enhance the rate of waste treatment as well as quantum of energy recovery las methane). Our experiments with various BSS options have revealed that r olls of nylon mesh (similar to 1mm openings), of 5 an height and 2 cm dia, when incorporated in CSTRs at the biofilm-surface : digests-volume ratio of 0.3 cm(2) cm(-3), enabled the CSTRs to perform better with up to 25% impro vement in methane yield. The studies, thus, reveal that simple devices of t he type used by us as BSS can significantly improve the performance of CST anaerobic digesters treating dairy wastes. The enhancement is evidently due to the development of active biofilms on the BSS which not only enhance th e contact of the water with micro-organisms but also reduce microbial washo ut. Further, such devices are inexpensive and very easy to incorporate - th e gains are thus achieved with very little cost and effort. BSSs were also found by us to enhance conversion of volatile fatty adds - derived earlier by us from aquatic weed water hyacinth - into methane-rich biogas.