Biofuel Production Along with Remediation of Sewage Water Through Algae

Abstract

The current study aims to formulate an alternative cost-effective sustainable wastewater treatment option for towns and cities in India through a comparative assessment of the treatment efficacy of mechanical treatment systems, facultative pond-based systems, and man-made lake systems based on physico-chemical and biological parameters. The key treatment parameters were analysed along with the assessment of total annual cost for operation of facultative pond and mechanical treatment systems. The results show that lake systems performed well under higher organic load with the removal efficiency of 70 % chemical oxygen demand (COD), 73 % total nitrogen (TN) and 22 % total phosphorus (TP). However, facultative pond-based systems were effective in the removal of up to 93 % suspended solid (SS) and 82 % biochemical oxygen demand (BOD). The conventional mechanical treatment removed 98 % SS, 74 % COD and 63 % BOD and is ineffective in the removal of nutrients. Furthermore, wastewater algae growing in lakes and ponds showed better lipid content (25–28 %) with suitable fatty acids (C16–C18 > 90 %). The FAME analysis showed high C16:0 (>40 %) followed by C18 fatty acids that further provides scope for algal biofuel generation to meet the regional energy demand. This necessitates an efficient algal capture mechanism to free the final treated effluent from algal BOD and solids and use of algal biomass as viable energy alternatives. Nutrient-integrated treatment efficiency (NITE) based on physical, chemical and biological factors has been devised for evaluating treatment efficiencies. Based on these efficiencies and cost of organic matter and nutrient removal for domestic wastewater treatment options, the best results were obtained for the lake and facultative algal pond-based systems which would be highly effective in Indian context and pave a way for sustainable wastewater treatment with resource recovery.