A combined heterotrophic and sulfur autotrophic denitrification technology for NO3--N wastewater treatment was started up by adding elemental sulfur in the heterotrophic denitrifying reactor, and the characteristics of pH constant and sludge reduction were studied. The results showed that the sulfur autotrophic denitrification bacteria in heterotrophic denitrifying reactor could achieve rapid growth. After running for 65d, TOC/N was controlled between 0.65 and 0.75, and the combined denitrification process did not require external alkalinity supplementation as the alkalinity need of autotrophic denitrifiers was supplemented by the heterotrophic denitrifiers. After running for 116d, the total nitrogen removal rate reached above 85%, and the denitrification efficiency was kept steady at 2.5 kg·(m3·d)-1. Compared to heterotrophic denitrification, the sludge production was greatly reduced, which was only 60% of that produced in combined heterotrophic and sulfur autotrophic denitrification reactor. NO2--N accumulated by using collaborative denitrification treatment of high concentration of NO3--N wastewater, the concentration reached 20 mg·L-1 even at the eventual plateau stage, which would require deep processing.
Keywords: autotrophic denitrification; coordination; heterotrophic denitrification; pH balance; sludge reduction.