Effect of food to microalgal biomass ratio on the assimilation of ammoniacal nitrogen from the secondary treated tannery effluent coupled with bio-energy generation using grown algal biomass

Microalgae are receiving great attention towards biofuel and potential option for the removal of nutrients from wastewater as an alternative biological treatment. In the current study, five different food to algal biomass ratios (0.25, 0.5, 1.0, 1.5, and 1.75) experimented with Chlorella vulgaris and a ratio of 1.0 was found to be optimum. Further studies were carried out in a lab-scale tubular photobioreactor (PBR). The maximum removal efficiencies of ammoniacal nitrogen, total Kjeldahl nitrogen, and total organic carbon were found to be 66.60%, 62.50%, and 69.09%, respectively. Grown microalgal biomass was subjected to biomethanation for recovery of bioenergy in the form of methane. The specific methane yield obtained was 233 mL/g VS (VS – volatile solids) added using a standard biomethane production test using automated methane potential test system II. The results of the study are promising, as it was observed that the coupling of both processes, that is, algal treatment integrated with anaerobic digestion of grown algal biomass will benefit wastewater treatment for nutrient removal as well as helps in energy production.