To treat sewage with low carbon source, a post-anoxic UCT step-feed process was proposed in a endogenous denitrification perspective. This process only added an anoxia section after the last aerobic section of the original UCT step-feed reactor, to strengthen the microbial consortium's storage capacity of carbon source. Under a very low ratios level of C/N (average C/N=3.1±1.5) in the wastewater influence, the post-anoxic UCT step-feed process achieved an average 75.3% of the TN removal rate; After 61days' operation, nitrogen removal content via simultaneous nitrification and denitrification (SND) was as high as 31.5%. At 40 th day, the carbon source storage level in the sludge was 12.2% higher than that of the original process, and 9hours specific endogenous denitrification rate (SEDR) was increased from 0to 5.56mgN/(gVSS·d), the process improved the TN removal rate mainly by simultaneous nitrification and endogenous denitrification (SNED) in the aerobic zone. The performance of sludge settling was improved: SVI value decreased from 350mL/g to 97mL/g, while sludge bulking still remained in the original UCT step-feed process. This process only added an anoxia section in the original reactor, without additional carbon source or nitrate liquid recycling facilities, which is convenient for reconstruction of the wastewater treatment plants.
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