Application of the phycoremediation process for tertiary treatment of landfill leachate and carbon dioxide mitigation

Landfill leachate contains a high concentration of organic and inorganic compounds, toxic heavy metals (THMs), ammonia and bio-refractory compounds. Hence, the remediation of landfill leachate is a challenge for environmental scientists and practitioners. Present work aims to study the application of phycoremediation process as tertiary treatment for pre-treated landfill leachate combined with carbon biosequestration in laboratory-scale photobioreactor (PBR) which can be easily scaled-up for on-site application. Real leachate collected from solid waste dumpsite was initially treated with coagulation and air-stripping process. The pre-treated leachate was innoculated with Chlorella pyrenoidosa and subsequently exposed different CO2 concentration to determine the optimum CO2 concentration for maximum biomass productivity. The results of the optimisation study were applied to a laboratory-scale PBR. The pre-treatment process effectively reduced the biologically inhibitive compounds and colour present in the raw landfill leachate which made it suitable for microalgae cultivation. Maximum biomass productivity of C. pyrenoidosa cultivated in pre-treated landfill leachate was observed when exposed to 10% CO2. The phycoremediation process in PBR effectively consumed 91% of DOC, 86% of TN, 90% of NH4-N and 96% of phosphates from pre-treated landfill leachate and also 0.26 g/L/day of CO2 from the air to produce 2.9 g/L of biomass. Results of the study indicated that using phycoremediation for tertiary treatment of landfill leachate can be a sustainable option as residual nutrients were consumed by microalgae for beneficial biomass production and provided superior quality effluent with minimal environmental hazards.