Cultivating Microalgae in Domestic Wastewater for Biodiesel Production

Abstract

The objective of this study was to evaluate the growth of nine species of microalgae (green and blue green microalgae) on domestic wastewater obtained from Zenein Wastewater Treatment Plant (ZWWTP), Giza governorate, Egypt. The species were cultivated in different wastewater treatments namely: without treatment; after sterilization; with nutrients with sterilization and with nutrients without sterilization. The experiment was conducted in triplicate and cultures were incubated at 25±1°C under continuous shaking (150 rpm) and illumination (2000 Lux) for 15 days. Algal growth parameters i.e., pH, electric conductivity (EC), optical density (OD), dry weight (DW) and chlorophyll-a (Ch-a) were measured at zero-time and at the end of the experimental period; while, the percentages of total lipids, biodiesel and the residual sediments (glycerine, pigments, etc) were determined in the harvested algal biomass. The data revealed that domestic wastewater with nutrients and with sterilization (T 3) was promising for cultivating five algal species as compared to the synthetic media. Moreover, the sterilized-domestic wastewater (T 2) was the selective medium for cultivating Oscillatoria sp. and Phormedium sp; however, T 1 medium (wastewater without treatment) was the promising medium for cultivating Nostoc humifusum. Biodiesel production from the algal species cultivated in synthetic media was ranging between 3.90% (Wollea saccata) and 12.52% (Nostoc muscorum). On the other hand, the highest biodiesel production from algal biomass cultivated in wastewater was obtained by Nostoc humifusum (11.80%) when cultivated in wastewater without treatment (T 1) and the lowest (3.80%) was recorded by Oscillatoria sp. when cultivated on the sterilized-domestic wastewater (T 2). The results of this study suggest that cultivating microalgae on domestic wastewater combines nutrients removal and algal lipid production for potential use as a biodiesel feedstock. Additionally, using the domestic wastewater, as nutrient media for microalgae cultivation, is suitable and non-expensive method as compared to the conventional cultivation methods for sustainable biodiesel and glycerol production.