Study On SNAD Coupled With SSuDA For Treating Anaerobic Digester Liquor Of Swine Wastewater

Swine wastewater has a large amount of water and a high concentration of pollutants;the anaerobic treatment effluent has the characteristics of low C/N ratio and high ammonia nitrogen（NH₄⁺-N）water quality,and the traditional nitrification-denitrification process is very expensive.The simultaneous partial nitrification anammox and denitrification（SNAD）denitrification process has low energy consumption,low sludge yield and high denitrification efficiency,but the total nitrogen（TN）concentration in the effluent is still at high level when treating swine wastewater.Therefore,the simultaneous partial sulfur autotrophic denitrification and anammox（SSu DA）process was set up at the back end of SNAD,which could further remove TN in swine wastewater.In this paper,high-throughput sequencing analysis of the microbial community in SNAD system and SSu DA system was carried out to clarify the structural characteristics of the microbial community in the system and provide a new idea for treating anaerobic digester liquor of swine wastewater.According to the water quality characteristics of the anaerobic liquid of swine wastewater,the coagulation sedimentation-anaerobic hydrolysis-SNAD-SSu DA coupling denitrification process was used for treatment.Suspended solids（SS）were removed by coagulation and sedimentation of the anaerobic digester liquor first.An anaerobic hydrolysis（An HA）unit was set up after the coagulation and sedimentation unit to convert part of the organic matter into organic acid,which was used as an effective carbon source for subsequent heterotrophic denitrification;at the same time,the chemical oxygen demand（COD）in the water body was reduced to ensure suitable C/N ratio.The effluent from the An HA unit entered SNAD unit.Under the conditions of temperature 33±1°C,reflux ratio 50%,hydraulic retention time 48 h,C/N ratio 0.6,and dissolved oxygen（DO）0.10 mg/L,the effluent NH₄⁺-N,nitrate nitrogen（NO₃^--N）and COD concentrations were 35.3±3.4 mg/L,112.5±12.4 mg/L and 344.3±1.0 mg/L,respectively,and the total nitrogen removal efficiency was about 80%.The effluent from SNAD entered the SSu DA unit and operated under the conditions of adding 183 mg/L of sulfur,p H7.0-7.7,temperature 33±1°C,reflux ratio 50%,and hydraulic retention time 48 h.It was successfully started after only 5 days.After the stable operation of the SSu DA system,the concentrations of NH₄⁺-N,NO₃^--N,TN and COD in the effluent were stabilized at 2.8±1.9mg/L,2.7±1.1 mg/L,6.2±2.3 mg/L and 223.0±2.2 mg/L,respectively.The SNAD coupled with SSu DA process could efficiently degrade the anaerobic digester liquor of swine wastewater,and the total nitrogen removal rate was as high as 98%.The results of high-throughput sequencing showed that the main functional bacteria genera in the activated sludge in the An HA reactor were Fastidiosipila,Clostridium and Thermovirga,with relative abundances of 15.09%,6.98%and 6.26%,respectively.In SNAD reactor,the activated sludge was mainly composed of Nitrosomonas,Denitratesoma,Hyphomicrobium and Ottowia,and the relative abundances of Candidatus＿Brocadia and Candidatus＿Kuenenia in the biofilm were 4.71%and 0.79%,respectively.The relative abundances Thiobacillus and Denitratesoma in SSu DA system were 17.93%and 1.61%,respectively.The functional bacteria in the biofilm were mainly autotrophic denitrifying bacteria（Thiobacillus）and anammox bacteria（Candidatus＿Brocadia）,with relative abundances of 21.81%and 1.95%.It showed that anammox bacteria are mainly distributed on the biofilm in SNAD system,aerobic ammonium oxidizing bacteria（Nitrosomonas）and heterotrophic denitrifying bacteria（Denitratesoma,Hyphomicrobium and Ottowia）mainly existed in activated sludge;in SSu DA system,sulfur autotrophic denitrifying bacteria（Thiobacillus）was distributed in the activated sludge and biofilms,while the anammox bacteria（Candidatus＿Brocadia）mainly existed in the biofilms.