Lipid and biodiesel production by cultivation isolated strain Chlorella sorokiniana pa.91 and Chlorella vulgaris in dairy wastewater treatment plant effluents.

The present study provided a comparison of two species of microalgae growth in dairy wastewater treatment plant effluents. In optimum conditions their operation to biomass production, lipid accumulation and fatty acids methyl ester composition so as to biodiesel production is studied. For the first time, the not sterilized effluents of dairy wastewater treatment plant was used as the culture mediums of native microalgae, Chlorella sorokiniana strain pa.91, and another one Chlorella vulgaris. They were cultured under 5 light intensity levels so as to find optimum conditions to observed high biomass and lipid production. At the optimum light intensity the composition of fatty acids methyl ester in their lipids was analyzed by GC-MS. The light intensity of 7500 Lux was obtained as the optimum for both microalgae to produce high biomass. The biomass productivity of C. sorokiniana pa.91 and C. vulgaris in preliminary treated effluent at this light intensity was obtained 0.233 and 0.214 g L-1 day-1, respectively. This parameter in secondary treated effluent was achieved 0.185 and 0.166 g L-1 day-1, respectively. Moreover, the highest lipid content of their biomass was observed at the light intensity of 2500 Lux. At this light intensity and at the preliminary effluent the maximum lipid content of C. sorokiniana pa.91 and C. vulgaris was observed 31% and 34%, respectively and at the secondary one it was obtained 35% and 36.67%, respectively. Based on the results, the fatty acids composition in the lipids of microalgae C. sorokiniana pa.91 and C. vulgaris cultured in both effluents had the high amount of cetane number which is really useful for high quality biodiesel production. Also, the other valuable properties which produce the high quality biodiesel were the obtained amounts of CFPP and CP which shown a high performance potential biodiesel even at low temperatures. This feature was obtained, on the grounds that the unsaturated fatty acid was obtained more than saturated fatty acid. The nutrients-rich media of dairy wastewater effluents were applicable to growth both microalgae and useful biomass production, lipid accumulation and fatty acids profiling. Furthermore, the compounds of fatty acids had the best conditions to biodiesel production especially in cold weather areas. © Springer Nature Switzerland AG 2020.