Ultrasonic enhanced simultaneous algal lipid production and nutrients removal from non-sterile domestic wastewater

Highlights: • Non-sterile domestic wastewater was proper substrate for algal lipid production. • Ultrasonic treatment markedly enhanced the energy production and nutrients removal. • Ultrasonic irradiation accelerated the formation of favorable microbial community. • Algal lipid yield in ultrasonic system significantly rose from 166.7 to 240 mg L⁻¹. -- Abstract: The lipid production and nutrients removal of Scenedesmus sp. in non-sterile domestic wastewater were investigated in the present study. Compared with secondary effluent, primary effluent was more appropriate substrate for algal growth, and the biomass concentration and lipid yield reached 0.69 ± 0.02 g L⁻¹ and 166.7 ± 8.3 mg L⁻¹, respectively. Ultrasonic exposure significantly enhanced the lipid yield and wastewater treatment performance. The biomass and lipid accumulation increased to 1.56 ± 0.07 g L⁻¹ and 240 ± 9.2 mg L⁻¹ at the optimum ultrasonic treatment frequency of 18 Hz, power of 20 W and time of 10 min. The maximum TN and TP removal rates reached 96.8% and 97.7%, respectively. Microbial community analysis revealed that the ultrasonic treatment markedly affected the microbial communities, which can accelerate the formation of favorable microbial community structure. Gemmobacter and Porphyrobacter were identified as key bacteria under ultrasonic condition, and their relative abundances were 38.7% and 19.1%, respectively. This research showed the efficiency of ultrasonic treatment in promoting algal lipid yield and domestic wastewater treatment.