Study On Intergrated Process Based On SNAD For Treating Wastewater With High Ammonia And Low C/N Ratio

Recently,urban sewage plant and household waste expended greatly lead to the increasing output of wastewater with high ammonia and low C/N ratio such as sludge digester and landfill leachate.Simultaneous partial nitrification,anammox and denitrification-integrated fixed film activated sludge（SNAD-IFAS）process has been became the research hotspot in the field of biological denitrification since the advantages of high efficiency,energy-saving and simultaneous removal nitrogen and carbon.However,the practical application of SNAD process was still lack of theoretical basis since most of the researches were used synthetic wastewater,while few reports focused on the actual wastewater.Therefore,in this study,SNAD integrated techniques were designed to treat sludge digester and landfill leachate.The control strategy,microbial activity and community structure of SNAD reactors were investigated,aiming at providing technical guidance for the engineering application of anammox technology.Firstly,integrated process contained anaerobic digestion,two-step tandem-type SNAD-IFAS and A²O² was applied for treating sludge digester.The temperature,reflux ratio and hydraulic retention time of SNAD1 and SNAD2 were controlled at 32℃,1:1 and 36 h,respectively.The DO concentrations of the two reactors were 0.15-0.35 mg/L and 0.1-0.2mg/L,while pH were maintained at 7.7-7.8 and 8.0-8.1,respectively.Without the addition of carbon resource,the system could deal with raw water with 1256.7 mg/L ammonia on day 98.The ammonia and total nitrogen in the effluent were 82.3 mg/L and 100.9 mg/L with removal efficiency of 98.8%and 92.0%,respectively.High-throughput sequencing showed that nitrite bacteria（AOB）,anaerobic ammonia-oxidizing bacteria（AnAOB）and denitrifying bacteria（DNB）coexist in the system.AOB mainly grows in activated sludge,while AnAOB and DNB enriched on biofilms.The abundance of AnAOB in SNAD1 and SNAD2 was 28.41%and 30%on day 100.The specific anammox activity（SAA）on biofilms were 68.72 mg TN/g VSS·h and 42.15 mg TN/g VSS·h in the two reactors which showed fabulous performance.While,the SAA in suspended sludge was negligible,but the specific aerobic oxidation activity（SAOB）reached 28.04 mg NO₂^--N/g VSS·h and 3.55 mg NO₂^--N/g VSS·h,respectively.Then,the treatment capacity of landfill leachate by anaerobic digestion and two-step tandem-type SNAD-IFAS was investigated.The temperature,pH and stirring speed of the anaerobic reactor were controlled at 32℃,8.0-8.3 and 10 r/min,respectively.The removal rate reached 44.9%since the influent and effluent concentration of COD was 3680.2±203.4mg/L and 2028.3±85.6 mg/L,and the C/N ratio in effluent was stable at about 1.3 under the condition of HRT maintained at 24 h.The SNAD reactor was fed by diluting water from anaerobic effluent,and the removal rate reached 83.8%and 39.4%when the influent TN and COD were 602.3 mg/L and 878.1 mg/L,respectively.The results of high-throughput sequencing showed that AnAOB（Candidatus-Kuenenia and Candidatus-Brocadia）was the dominant species on biofilm,which abundance in the two reactors was 26.21%and 30.82%,respectively.While AOB mainly exists in suspended sludge which abundance was 5.91%and1.24%,respectively.