Abstract:
Issues concerning sustainable wastewater treatment can be found almost in every scientific, social, or political agenda all over the world. Untreated industrial and household wastewater still being dumped in watercourses and leachate from the landfilling sites are the factor leading to dwindling of clean water. The energy demand all over the globe is also increasing continuously. The expected depletion of fossil fuels within a century or so has compelled the global community to seek renewable energy sources. Biofuels produced from biomass are the most promising source and anticipated to satisfy the escalating global energy demands. In this study microalgae, the unicellular robust organisms, which are capable of growing in all types of environment, have been proposed as an alternative biological treatment for wastewater and leachate with the added benefit of lipids extraction for formation of biodiesel. For this purpose, four local microalgal strains S1, S2, S4 and S6 were evaluated for their potential to grow and treat wastewater and leachate. The microalgal biomass collected after the treatment was used for lipids extraction and biodiesel production through transesterification. It was found that all four strains were able to grow well in 100% wastewater and up to 50% leachate concentration. The results indicated more than 83.3% and 91.7% removal of NO3-N, PO4 and COD from wastewater and leachate, respectively, with slight variation among all strains. While in case of heavy metals, S1 showed the highest cumulative removal of 63% from wastewater and 52.9% from leachate. Maximum lipids yield, extracted using chloroform: methanol solvent was 20.5%, given by S6. Whereas highest convertible lipids into biodiesel were obtained from S4, with 93% biodiesel yield through direct transesterification by using methanol in the presence of H2SO4 as a catalyst. GC-MS analysis showed 89% and 85.5% conversion of microalgal lipids into alkyl esters, by strains S4 and S6 respectively. This study concluded that selected microalgal strains can be used for the treatment of both, domestic wastewater and leachate. Additionally strains S4 and S6 have the potential to provide the added benefit of biodiesel production.
