Abstract:During biological nitrogen removal process treating landfill leachate by using short-cut nitrification and denitrification technology, high concentration of free ammonia (FA) can inhibit the activity of ammonia oxidizing bacteria (AOB), reduce the nitrosation rate and nitrogen removal efficiency. In this study, step feeding strategy was used to reduce the inhibition of FA on AOB and thereby improve the nitrogen removal efficiency because of the rational distribution of the substrates and decrease of the substrate/microorganism ratio and FA content. The result showed that the stable short-cut nitrification and denitrification was successfully realized through controlling the DO concentration below 1.0 mg·L?1, and the nitrite accumulation rate (NAR) reached 84.97% at the hydraulic retention time (HRT) of 6.25 d. When HRT was shortened to 5.5 d, the ${\rm{NH}}_4^ + $-N removal rate decreased to about 69.63%, and nitrogen removal efficiency (NRE) was 18.06%. It found that FA concentrations in the O1 and O2 tanks were higher than 36.32 mg·L?1, which exceeded the AOB inhibitory concentration limit, and the short-cut nitrification process was inhibited. After step feeding mode was used, ${\rm{NH}}_4^ + $-N removal rate was 89.86% at HRT of 5.5 d, and NRE was 27.62% which was 52.93% higher than that before step feeding. When HRT was shortened to 5.0 d, the ${\rm{NH}}_4^ + $-N removal rate was still higher than 81.25%. FA concentrations in O1 and O2 tanks decreased to 7.91 mg·L?1 and 5.81 mg·L?1, respectively in the step feeding process. Under this condition, FA could effectively inhibit NOB while didn’t severely inhibit AOB. After supplementing the carbon source according to C/N=4, the NRE of the system reached about 80%. The microbial sequencing results showed that the relative abundances of AOB in O1, O2, O3 and O4 tanks were 2.27%, 1.77%, 2.75% and 1.37%, respectively, which increased by 12.37%, 68.57%, 57.14% and 59.30% compared with the process without step feeding mode. This further indicated that the step feeding process was beneficial for the growth of AOB and short-cut nitrification process. The above results showed that for the treatment of landfill leachate, the step feeding strategy can effectively improve the short-cut nitrification and nitrogen removal efficiency, and it’s valuable for practical application. Key words:landfill leachate/ biological nitrogen removal/ short-cut nitrification and denitrification/ free ammonia/ step feeding.
图1实验装置示意图 Figure1.Experimental setup used in this study
图4分点进水对短程硝化反硝化脱氮系统运行性能的影响 Figure4.Impact of step feeding mode on nitrogen removal performance in the short-cut nitrification and denitrification system
图6门级分类中种泥和驯化后污泥中细菌群落的相对丰度 Figure6.Relative abundance of bacterial communities in seed sludge and domesticated sludge in different phylum level classifications
图7属级分类中分点运行前后污泥中细菌群落的相对丰度变化 Figure7.Variation of the relative abundance of bacterial communities in sludge before and after step feeding operation in different genera
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1.School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, China 2.Jiangsu Key Laboratory of Anaerobic Biotechnology, Wuxi 214122, China 3.Wuxi City Environmental Technology Co. Ltd., Wuxi 214026, China Received Date: 2020-10-10 Accepted Date: 2020-11-16 Available Online: 2021-05-23 Keywords:landfill leachate/ biological nitrogen removal/ short-cut nitrification and denitrification/ free ammonia/ step feeding Abstract:During biological nitrogen removal process treating landfill leachate by using short-cut nitrification and denitrification technology, high concentration of free ammonia (FA) can inhibit the activity of ammonia oxidizing bacteria (AOB), reduce the nitrosation rate and nitrogen removal efficiency. In this study, step feeding strategy was used to reduce the inhibition of FA on AOB and thereby improve the nitrogen removal efficiency because of the rational distribution of the substrates and decrease of the substrate/microorganism ratio and FA content. The result showed that the stable short-cut nitrification and denitrification was successfully realized through controlling the DO concentration below 1.0 mg·L?1, and the nitrite accumulation rate (NAR) reached 84.97% at the hydraulic retention time (HRT) of 6.25 d. When HRT was shortened to 5.5 d, the ${\rm{NH}}_4^ + $-N removal rate decreased to about 69.63%, and nitrogen removal efficiency (NRE) was 18.06%. It found that FA concentrations in the O1 and O2 tanks were higher than 36.32 mg·L?1, which exceeded the AOB inhibitory concentration limit, and the short-cut nitrification process was inhibited. After step feeding mode was used, ${\rm{NH}}_4^ + $-N removal rate was 89.86% at HRT of 5.5 d, and NRE was 27.62% which was 52.93% higher than that before step feeding. When HRT was shortened to 5.0 d, the ${\rm{NH}}_4^ + $-N removal rate was still higher than 81.25%. FA concentrations in O1 and O2 tanks decreased to 7.91 mg·L?1 and 5.81 mg·L?1, respectively in the step feeding process. Under this condition, FA could effectively inhibit NOB while didn’t severely inhibit AOB. After supplementing the carbon source according to C/N=4, the NRE of the system reached about 80%. The microbial sequencing results showed that the relative abundances of AOB in O1, O2, O3 and O4 tanks were 2.27%, 1.77%, 2.75% and 1.37%, respectively, which increased by 12.37%, 68.57%, 57.14% and 59.30% compared with the process without step feeding mode. This further indicated that the step feeding process was beneficial for the growth of AOB and short-cut nitrification process. The above results showed that for the treatment of landfill leachate, the step feeding strategy can effectively improve the short-cut nitrification and nitrogen removal efficiency, and it’s valuable for practical application.
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