Influential Factors And Deep Nitrogen Removal Characteristics Of SNEDPR Coupled Anammox System

Municipal wastewater has the characteristics of low C/N,and the traditional nitrogen and phosphorus removal process can not meet the current treatment and discharge standards.Simultaneous nitrification-endogenous denitrification and phosphorous removal system can realize nitrogen and phosphorus removal of municipal wastewater through"one carbon multipurpose".The subject studied the influence of different influencing factors on the SNEDPR system,in order to provide more theoretical support for SNEDPR stable operation and application promotion.In addition,the sludge digestion liquid of sewage treatment plant is rich in various short-chain fatty acids（SCFA）and NH₄⁺-N and the C/N is low by about 1,usually return sludge digestion liquid to the mainstream for denitrification for treatment,causing waste of carbon sources or affecting effluent water quality.The effects of the influent concentration and operation mode on the enrichment of anaerobic ammonia oxidizing bacteria（Anammox）and the inhibition of nitrite oxidizing bacteria（NOB）in simultaneous nitrification,anammox and denitrification system were also studied,and the flocs and biofilms were analyzed by high-throughput sequencing.Analyzed the changes in the flora structure and discussed the potential application of the SNAD-IFAS system in the lateral treatment of sewage treatment plants.The main research contents and conclusions were as follows:（1）Adopting SBR process,inoculating ordinary activated sludge,with delayed aerobic/anoxic（A/O）operation mode（each cycle is 6 h,in which water inflow is 10 min,delayed anaerobic 180 min,aerobic 150 min,precipitation 10 min,drainage 10 min）.Firstly,the SNEDPR system was started when the COD of the influent was 600 mg/L（C/N=10）;secondly,by adjusting the COD concentration of the influent,the nitrogen and phosphorus removal performance of the SNEDPR system was investigated by different COD concentrations of the influent Impact.The test results show that when the influent COD concentration is 600 mg/L（C/N=10）,the start-up of the SNEDPR system and deep nitrogen and phosphorus removal can be achieved.The average concentration of effluent TN and PO₄^3--P was 8.10 mg/L and 0.10 mg/L respectively.The average removal rate of PO₄^3--P,TN and simultaneous nitrification endogenous denitrification（SNED）were 99.79%,89.38%58.00%.As the COD concentration（C/N）of the influent decreased,the performance of the SNEDPR system for nitrogen and phosphorus removal gradually deteriorated.When the COD concentration of the system influent dropped from 600 mg/L to 150 mg/L,the TN concentration of the effluent increased to 20.98 mg/L,and the SNED rate decreased to 5.90%;anaerobic phosphorus release（PRA）and aerobic phosphorus absorption（PUA）gradually decreased,the removal rate of PO₄^3--P dropped to 40.62%.（2）Adopting SBR process,inoculating activated sludge（inoculated sludge took from the stable SNEDPR system of Qingdao University）,with delayed aerobic/anoxic（A/O）operation mode（same as the above operation cycle）.By adjusting the NH₄⁺-N concentration of the influent,the effect of different NH₄⁺-N concentrations on the nitrogen and phosphorus removal of the SNEDPR system was explored.The test results show that the SNEDPR system has a strong adaptability to the impact load of NH₄⁺-N.The NH₄⁺-N concentration of the influent continued to increase,and the PRA continued to decrease,but the phosphorus removal effect was not affected,still less than 0.50 mg/L.And TN removal rate and SNED rate remained stable.When the concentration of influent NH₄⁺-N is 140 mg/L,the effluent quality of the system is obviously deteriorated.The average value of NO₂^--N in the effluent was 5.95 mg/L,forming NO₂^--N accumulation.The TN of the effluent was as high as 18.62 mg/L,and the average value of PO₄^3--P was2.55 mg/L.（3）In the integrated fixed-biofilm activated sludge reactor,inoculate short-range nitrification flocs sludge,the operating conditions were as follows:during 1-117 d,use aerobic/anoxic（1-47 d,6 h/12 h,48-117 d,6 h/24 h）operating mode,during 118-262d,intermittent aeration operation mode（low oxygen aeration 7 min,anoxic stirring 21 min）,DO=0.7-1.0 mg/L（118-222 d）,1.0-1.3 mg/L（223-262 d,Table 1.2）.The test results show that the SNAD-IFAS system was started by using short-nitrification suspended sludge as seed sludge.After 85 days of operation,the anoxicΔNH₄⁺-N:ΔNO₂^--N concentration was close to 1:1.32.In a cycle,the ratio of the amount NO₃^--N produced/NH₄⁺-N consumption was 0.03,the COD removal rate was higher than 90%,and the color of the biofilm became red-brown.Using intermittent aeration mode and temporarily increasing the concentration of NH₄⁺-N in the influent（free ammonia,FA）inhibited the proliferation of NOB,and the concentration of NO₃^--N in effluent gradually decreased.Further optimized the overall treatment efficiency of the SNAD-IFAS system,Increasing the DO concentration of the system to 1.00-1.30 mg/L,the TN concentration of the effluent<15 mg/Land improved the TN removal rate of the system.Based on the above research,a promising solution can be proposed for the treatment of sludge digestion liquid and municipal sewage through the SNAD-IFAS system in the side stream of the WWTP（Figure 5.6）.The system ran sampling at 1 d,55 d,175 d and 262 d,and conducted high-throughput measurement of its flocs and biofilm mixture liquid,analyzed the flora structure.High-throughput sequencing analysis was showed that uncultured＿f＿Nitrosomonadaceae-AOB was mainly present in the flocs,and the relative abundance of OTU was 2.40%.The main anaerobic ammonia-oxidizing bacteria was Candidatus＿Brocadia,the relative abundance of OTU 2.93%,the relative abundance of OTU in biofilms was 7.67%,which proved that anaerobic ammonia oxidizing bacteria can spontaneously and remain in the SNAD-IFAS system.