DENITRIFICATION ENHANCEMENT EFFECT AND MICROBIAL FLORA ANALYSIS OF A NEW BIOMASS CARBON SOURCE

To achieve the deep denitrification effect of wastewater treatment plants, taking a sewage treatment plant in Taihu Lake Basin as an example, the biomass carbon source with derivatives of biomass waste as the main raw material was used as the electron donor for denitrification, and the denitrification effects of the anoxic tank and deep-bed filter were studied respectively. The changes in microbial community structure before and after the addition of carbon sources were also analyzed. The results showed that 1.67~1.73 mg/L nitrate could be removed, when the biomass carbon source dosage was 2.5~3.0 t/d, and the removal rate was about 52%~68%. Meanwhile, the deep bed filter consumed about 5.27 mg COD for every 1 mg NO₃^--N removal after adding biomass carbon source in the process of denitrification. Thus, the effluent TN was stable and met the discharge limit requirements of class Ⅰ and Ⅱ protected areas in the Discharge Standard of Main Water Pollutants for Municipal Wastewater Treatment Plant & Key Industries in Taihu Area(DB 32/1072—2018). Through 16 S rRNA gene sequence analysis, it was found that the dominant microbial phyla of hypoxic pools and deep-bed filters were Proteobacteria, Actinobacteria, Chloroflexi, and Bacteroidota. After adding biomass carbon source to deep-bed filter with different process conditions and growth environment, the dominant flora with denitrification function such as Thiothrix, Bacillus, Propionicicella, norank_f_Rhodocyclaceae and Terrimonas were more prominent and further effectively ensured the stable deep nitrogen removal performance of the system. At the same time, the adding of biomass carbon source indirectly reduced carbon dioxide emissions, which made a positive contribution to carbon emission reduction and carbon neutralization.