Treatment of fracturing wastewater using microalgae-bacteria consortium

The symbiotic relationships between Chlorella vulgaris and Bacillus bacteria in fracturing wastewater treatment were evaluated under different conditions, including varying dilution ratios of fracturing wastewater (2-4), dosages of bacteria (20-80 mg/L), and pH (6.5-8.5). The effects of process variables on the response of algal density were optimized and studied via the Box-Behnken response surface design. The individual and interactive effects of process variables on the response were investigated by a second-order polynomial model and three-dimensional response surface plots. The optimal treatment conditions were a dilution ratio of 2, bacteria dose of 72.13 mg/L, and pH of 6.5, and the maximum biomass concentration of Chlorella vulgaris was 2.23 g/L. Bacillus bacteria increased the activity of superoxide dismutase (SOD) and acetyl-CoA carboxylase (ACCase) of Chlorella vulgaris. Compared to the free Chlorella vulgaris, the co-cultivation of Chlorella and Bacillus bacteria dimprove the algal growth and degradation of organic pollutants.