Cultivation of Chlorella for biomass production and nutrient removal from unsterilized human urine containing washing powder wastewater

Human urine accounts for less than 1% of domestic sewage while contributes about 80% of nitrogen and 50% of phosphorous. The source-separated human urine featuring high nutrients and low impurities, turbidity, and pathogenic bacteria is a high-quality microalgae culture medium whereas frequently mixed with flush water containing washing powder and usually overdiluted or sterilized before culturing microalgae. The work presented here aimed to assess the Chlorella pyrenoidsa (FACHB-5) and Chlorella sp. (FACHB-1554) cultivation in unsterilized human urine containing washing powder wastewater in terms of the biomass and protein production and the removals of nitrogen, phosphorus, and chemical oxygen demand. FACHB-5 and FACHB-1554 could eliminate 84.79% and 96.33% ammonium nitrogen, 83.66% and 95.18% total nitrogen, 85.77% and 96.32% total phosphorus, and 38.53% and 86.86% chemical oxygen demand from human urine under 40% of human urine wastewater addition ratio and no washing powder wastewater addition and achieved 0.5 and 1.01 g/L biomass yields and 60% and 50% protein contents. The washing powder wastewater significantly inhibited the growths of FACHB-5 and FACHB-1554. As the washing powder wastewater addition ratio increased, the yield of FACHB-5 decreased while the production of FACHB-1554 followed a tendency to rise and then fall. FACHB-1554 was more tolerant to human urine and washing powder wastewater than FACHB-5, and 1% and 2% of washing powder wastewater addition ratios were relatively optimal for FACHB-5 and FACHB-1554 to reach 0.32 and 0.45 g/L of yields and alike 53% of protein contents. Under the conditions, the removals of ammonium nitrogen, total nitrogen, total phosphorus, and chemical oxygen demand reached 66.25%, 64.33%, 65.31%, and 32.53% for FACHB-5 and 76.16%, 74.36%, 75.15%, and 42.31% for FACHB-1554, respectively. Studies revealed the feasibility of cultivating microalgae in a high concentration of unsterilized source-separated human urine wastewater, which might be a promising low-cost approach for realizing the scale production of microalgae, purifying domestic wastewater, and promoting the development of value-added biofuels, microalgae protein, and other industries.