Study on microbial metabolic mechanism of activated sludge denitrification by A2O process under strong solar radiation in highland habitat

Abstract The effects of plateau solar radiation on microbial abundance and diversity and metabolism during the formal operation of the A²O reactor were analyzed by running three parallel A²O units with solar radiation, constant temperature and room temperature laterally. The results showed that when the formal operation reached the 180th day, the nitrogen removal effect of the solar radiation A²O reactor decreased significantly compared with that of the constant temperature and room temperature units in general; the number of operational taxonomic units (OTUs) in the solar radiation, constant temperature and room temperature A²O systems were 1140, 972 and 1000, and the solar radiation reactor showed an increasing trend throughout the whole process, and the metabolic function of the dominant genera of microorganisms was dominated by organic matter degradation, denitrification and denitrogenation, and the metabolic pathways were dominated by carbon and nitrogen metabolism, and it was also found that the relative abundance of denitrifying bacteria (DNB) increased with the increase in the duration of solar radiation exposure. The bacterial diversity of the solar A²O system was lower than that of the constant and room temperature systems up to 90 days, and the relative abundance of some common dominant genera in the sludge was suppressed by solar radiation, but the abundance of some denitrification-related genera and their functional genes were instead strengthened in the solar radiation reactor.