Water recycle system in an artificial closed ecosystem - Lunar Palace 1: Treatment performance and microbial evolution.

Water recycle systems have important implications to realize material circulation in biological regeneration life support systems, which is of significance for long-term space missions and future planetary base. Based on membrane biological activated carbon reactor (MBAR) technologies, the 'Lunar Palace 365' experiment established various treatment processes for condensate wastewater, domestic wastewater, urine, and used nutrient solutions. The 370-day operation data showed the COD index of purified condensate wastewater decreased to 0.74 ± 0.15 mg/L, which met the standards for drinking water quality. The average removal rate of organic contaminants in domestic wastewater by the MBAR was 85.7% ± 10.2%, and this MBAR also had a stable nitrification performance with effluent NO-N concentrations fluctuating from 145.57 mg/L to 328.59 mg/L. Moreover, the purification of urine achieved the conversion of urea-N to NH-N and thus the partial recovery of nitrogen. 16S rDNA sequencing results revealed the evolution of microbial diversity and composition during the long-term operation. Meiothermus, Rhodanobacter, and Ochrobactrum were the dominant microorganisms in various MBARs.