Effect Of Organic Carbon Source On Nitrite Accumulation During The Process Of Denitrification

Nitrite is the intermediate of denitrification process.High nitrite accumulation during denitrification could provide the electron acceptor for anaerobic ammonium oxidation（anammox）.Nitrite accumulation in the process of denitrification is closely associated with the microbial community.However,the microbial species composition of the denitrifying sludge is affected by the type of carbon source,the dosage of organic carbon and the cultivation period.And there are few studies on the amount of carbon source used in sludge cultivation,and further systematic studies are needed.In this study,sodium acetate,glucose and brewery wastewater were selected as carbon sources for denitrification,and the effects of carbon source type and dosage of organic matter on nitrite accumulation and microbial community during the process of denitrification were investigated.The main conclusions were as follows:（1）The nitrite accumulation performance and bacterial community structure of activated sludge（referred to as P₁ sludge and P₂sludge,respectively）,which was cultured with glucose as carbon source at C/N ratios of 3 and 5,respectively,were significantly different.Compared with P₁ sludge,the nitrite accumulation performance of P₂ sludge was better.When the temperature was 15℃～26℃,the nitrite accumulation rate of P₂ sludge was 37.21%～40.09%.Both kinds of sludge contain a lot of Thauera,but the relative abundance of Thauera were different greatly.The relative abundance of Thauera in P₁ sludge and P₂ sludge was 18.67%and 64.01%,respectively,at the incubation time of 220 d.（2）The activated sludge（referred to as Y₁ sludge and Y₂sludge,respectively）cultured with sodium acetate as the carbon source at C/N ratios of 3 and 5,respectively,has little difference in the nitrite accumulation performance and bacterial community structure.When the C/N ratio was 3～5 in the process of denitrification,both Y₁sludge and Y₂ sludge could realize high concentration of nitrite accumulation,and the maximum nitrite accumulation ratio of Y₁ sludge and Y₂ sludge was 67.16%～90.17%.At day 220,the relative abundances of Thauera in Y₁ sludge and Y₂ sludge were 81.53%and 86.05%,respectively.（3）The sludge taken from the biological treatment tank of the brewery sewage treatment station and the sludge cultured in our laboratory were used as inoculation sludge（referred to as S₁ sludge and S₂ sludge,respectively）.After 26 days of cultivation with brewery wastewater,the relative abundances of Thauera in S₁sludge and S₂ sludge were 33.03%and 34.49%,respectively.However,under the same C/N ratio,the nitrite accumulation performance was different greatly.At C/N ratio of 10,the maximum nitrite accumulation ratios of S₁ sludge and S₂ sludge were 27.61%and 67.71%,respectively.The experimental results of this study showed that compared with glucose,the nitrite accumulation performance of sludge cultured with sodium acetate as carbon source was more likely to produce nitrite accumulation during denitrification.When brewery wastewater was used as carbon source,a higher accumulation rate of nitrite could be obtained in the process of denitrification by selecting suitable inoculation sludge.Therefore,brewery wastewater was an ideal carbon source suitable for short-cut denitrification.