Bioremediation and nutrient removal from wastewater by Chlorella vulgaris

Abstract

The capability of the microalgae Chlorella vulgaris (Cv) for biomass production and nutrients removal under different wastewater quality has been studied. Cv was cultivated in a standard medium (Marine labs American society of microbiology-derived medium, MLA) blended with primary wastewater (PWW), secondary wastewater (SWW) and petroleum effluent (PE) in different volume ratios. Macro and micro nutrients were characterized in each solution, and the impact on the rate of biomass growth (specific growth rate, μ) and removal efficiency (RE) determined for the bulk nutrients (total nitrogen TN and total phosphorus TP) along with a range of macro- and micro-nutrients.

PWW, SWW and PE media were found to provide an appropriate quantity and balance of nutrients to promote significantly more rapid algal growth than the standard medium MLA, with high nutrient RE achieved at the end of cultivation period. Over a 13-day period the highest biomass concentration Xmax of 1.6 g L−1 was attained for PWW with corresponding values of 1.2 d−1, 80% and 100% for μ, and TN and TP RE respectively. μ decreased to 0.75 d−1 for a 75%:25% blend of PWW with MLA and to 0.54 d−1 on further decreasing the blend ratio to 25:75 PWW: MLA, with corresponding TN removal efficiencies of 85% and 76% respectively; 100% removal of TP was obtained throughout. There was a slight increase in Xmax, μ and TN removal of 1.16 g L−1, 0.62 d−1 and 83% respectively for SWW. The lowest Xmax of 0.64 g L−1 in PE was recorded was associated with values of 0.31 d−1, 79% and 100% for μ, and removal efficiencies of TN and TP respectively.