Eco-friendly cultivation of microalgae using a horizontal twin layer system for treatment of real solid waste...

Solid waste leachate (SWL) requires dilution with water to offset the negative effects of high nutrient concentration and organic compounds for its microalgae-based treatment. Among attached cultivation systems, twin layer is a technology in which limited information is available on treatment of high strength wastewater using microalgae. Moreover, widespread application of twin layer technology is limited due to cost of substrate and source layer used. In the present study, potential of Scenedesmus sp. for the treatment of SWL was assessed on horizontal twin layer system (HTLS). Novel and cost-effective substrate layers were tested as attachment material. Wetland treated municipal wastewater (WMW) was used to prepare SWL dilutions viz, 5%, 10%, 15%, 20% and 25% SWL. Recycled printing paper showed maximum biomass productivity of 5.19 g m^-2 d^-1. Among all the SWL dilutions, Scenedesmus sp. achieved maximum growth of 103.05 g m^-2 in 5% SWL which was 16% higher than WMW alone. The maximum removal rate of NH₄⁺ -N, TKN, and PO₄^3- P was obtained in 20% SWL which was 1371, 1588 and 153 mg m^-2 d^-1 respectively. Varying concentrations of nutrients in different SWL dilutions significantly affected lipid biosynthesis, with enhanced productivity of 2.28 g m^-2 d^-1 achieved in 5% SWL compared to 0.97 g m^-2 d^-1 in 20% SWL. Hence, it can be concluded that 5% SWL dilution was good for biomass and lipid production, while the highest nutrient removal rates were obtained at 20% SWL mainly attributed to biotic and abiotic processes. Based on these results HTLS can be a promising technology for pilot scale to explore industrialized application of wastewater treatment and algal production.