Phycoremediation coupled biomethane production employing sewage wastewater: Energy balance and feasibility analysis

In the present work Chlorella pyrenoidosa, Scenedesmus abundans and Anabaena ambigua have been evaluated for their biomass, phycoremediation efficiency and biomethane production potential by cultivating them in the primary treated sewage waste water (PTSWW) under controlled conditions. By the end of 25-day experiment, up to 52-88% reduction was observed in the nutrient concentration from the 3:1 ratio of PTSWW. Co-digestion of microalgal biomass (dry) with cow dung was performed to estimate biomethane potential. Biogas yield of 618-925 ml g^-1 VS with 48-65% of methane content was obtained employing the microalgal species cultivated in PTSWW. Microalgae appeared notably competent at nutrient sequestration from PTSWW with significant microalgal biomass productivity for biogas production. Energy balance studies revealed the feasibility of coupling the remediation with energy generation. High photosynthetic rate and biomass generation ability along with nutrient confiscation supports employment of microalgae as a potential next generation biofuel source with waste management.