Abstract
This work aimed to enrich a denitrifying bacterial community for economical denitrification via nitrite to provide the basic objects for enhancing nitrogen removal from wastewater. A sequencing batch reactor (SBR) with continuous nitrite and acetate feeding was operated by reasonably adjusting the supply rate based on the reaction rate, and at a temperature of 20 ± 2 °C, pH of 7.5 ± 0.2, and dissolved oxygen (DO) of 0 mg/L. The results revealed that the expected nitrite concentration can be achieved during the whole anoxic reaction period. The nitrite denitrification rate of nitrogen removal from synthetic wastewater gradually increased from approximately 10 mg/(L h) to 275.35 mg/(L h) over 12 days (the specific rate increased from 3.83 mg/(g h) to 51.80 mg/(g h)). Correspondingly, the chemical oxygen demand/nitrogen (COD/N) ratio of reaction decreased from 7.9 to 2.7. Both nitrite and nitrate can be used as electron acceptors for denitrification. The mechanism of this operational mode was determined via material balance analysis of substrates in a typical cycle. High-throughput sequencing showed that the main bacterial community was related to denitrification, which accounted for 84.26% in the cultivated sludge, and was significantly higher than the 2.16% in the seed sludge.
Highlights
Nitrogen-contaminated wastewater discharge is known as a main reason of eutrophication.Removing nitrogen from wastewater using specific facilities in wastewater treatment plants (WWTPs) is a useful approach to controlling this problem
Carbon sources are insufficient in low chemical oxygen demand/nitrogen (COD/N) ratio domestic wastewater to accomplish effective nitrogen removal
The color of the sludge changed from brown to black, which is the characteristic color of anaerobic sludge, after settling for approximately three days after being collected from the WWTP
Summary
Nitrogen-contaminated wastewater discharge is known as a main reason of eutrophication. Removing nitrogen from wastewater using specific facilities in wastewater treatment plants (WWTPs) is a useful approach to controlling this problem. Strict discharge standards of nitrogen are the tendency globally due to the increasingly serious issue of eutrophication [1]. The traditional nitrification–denitrification process has commonly been used for biological nitrogen removal in WWTPs. carbon sources are insufficient in low chemical oxygen demand/nitrogen (COD/N) ratio domestic wastewater to accomplish effective nitrogen removal. A large amount of expensive external carbon sources is needed for daily operation of WWTPs [2]
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