Simultaneous investigation on bioremediation and biodiesel recovery from tannery wastewater using marine microalgae

Abstract

Over the last few decades, the advancement in industrialization and technology have created considerable water demand. In addition, large amount of water was onsumed by the industries in various processes. On the other side, strict rules and regulations of wastewater management insist in adopting strategies for recovery or reuse of water and energy resource. Hence, the current situation emphasises the modernisation of wastewater management with appropriate approach for the recovery of water resource. The recent studies on the potential for treatment of wastewater and simultaneous energy recovery by bioremediation is in limelight. Single Cell Oil (SCO) producing oleaginous microbes can be engaged in the production of microbial fuels by transesterification. Therefore, dual benefit of energy generation and waste minimisation can be accomplished in this practice. In the current study, the secondary effluent from the tannery wastewater treatment plant was taken as nutrient medium for four different strains of marine micro algae capable of producing lipids over 20% of its cell dry weight. Chlorella marina, Nannochloropsis salina, Thalassiosira sp, and Dunaliella salina were the marine algae considered for the research work. The feasibility study was done in order to confirm the ability of the four microalgal species in utilizing secondary effluent as feed material for lipid production within its cellular mass and found to be satisfactory. The Fourier Transform Infrared Spectroscopy analysis confirmed the production of triacyl glycerol by the microbial strains. Hence further study was done to optimize the culture conditions such as Temperature (ºC), Light intensity (Lux), Carbondioxide concentration (%) and Nitrogen concentration (mmol/L). A batch reactor was fabricated to provide the required culture conditions. Under the optimized culture condition of 27 ºC, 1730 Lux, 8% CO2 concentration and 6 mmol/L Nitrogen concentration Chlorella marina gave maximum biomass and lipid yield of 7.3 g/L and 3.2 g/L respectively. The