Study of microalgae growth and lipids content using waste water as medium

Abstract

Nowadays there is great and continuous increase in industrialization, infrastructure and urban- expansions, which has contributed to a significant wastes demand and water shortage due to water pollution. Industry including agro-based industry is one of the major sectors discharging great amount of waste water annually affecting the other water sources from one hand and the human life from another hand. Palm oil industry in Malaysia is producing the largest organic pollutant loads into rivers. Palm oil mill effluent (POME) is highly polluted waste, having unpleasant smell and containing high amount of pollutants. There is great need to find alternative way on how to utilize those organic pollutants for the good benefit of both human being and environment. Microalgae are unicellular, photosynthetic microorganisms having the ability of both reducing the amount of pollutants from these waste waters and giving rapid biomass growth which can be great source for many biofuels and renewable green energy. Major drawback growing these microorganisms in waste water is low amount of biomass due to deplete of the essential nutrients. This can be adjusted by supplementing the waste water with addition of the essential nutrients in order to enhance the growth. This study aims at growing microalgae source of biofuel in the biologically treated POME and identification of bioremediation role of these microorganisms. The first step of this study consisted of screening two microalgae strains namely: Botryoccocus sudeticus and Chlorella vulgaris are two microalgae species knowing by their high lipids content and biomass growth. When comparing the results B sudeticus seemed to be a better source for biofuel production due to higher lipids content reaching 26.6%. The same microalgae was used for evaluation of the media components for biomass production using full factorial design and optimisation of the biomass growth by using central composite design. The results showed that the presence of the organic carbon, nitrogen and phosphorus can increase the growth significantly and all of these three nutrients were having positive effects on the growth of the biomass. This biomass was optimized to reach 2.35g/l with R2= 0.9414. The waste water used to grow the algae was characterized before and after the biomass collection and it was found that these microorganisms reduced the BOD, COD, TOC, TN and TP to 75%, 51.75%, 54.54%, 44.20%, and 57.6% respectively. The growth curve was also determined by measuring the daily optical density and the total suspended solids in the medium of the growth with and without addition of nutrients. Finally, the fatty acids in the final extracted lipids were also identified and it was found that the algae oil contains saturated fatty acids represented by caproic acid, palmitic acid and stearic acid. However the unsaturated fatty acids found were: palmitoleic acid and oleic acid. Botryoccocus sudeticus can be grown on biologically treated POME and its oil can be a good candidate for biodiesel production due to higher level of unsaturated fatty acids as compared to saturated fatty acids.