Partial Denitrification Based On Brewery Wastewater As Carbon Source And Nitrogen Removal Via Combining Partial Denitrification With Anammox

The cost of traditional biological nitrogen removal process is high because of the external carbon source required,especially for low COD/N wastewater treatment.Anaerobic ammonia oxidation（ANAMMOX）process possesses the advantages of low consumption,no demand of organic carbon source,low sludge yield and low operating cost,which is suitable for the treatment of low COD/N sewage.Previous studies typically adopted partial nitrification process to provide NO₂^--N for ANAMMOX.However,partial nitrification was unstable in long-term operation due to the inevitable oxidation of NO₂^--N to NO₃^--N.NO₂^--N is an intermediate of the denitrification process.Thus,partial denitrification（NO₃^--N→NO₂^--N,PD）can be used to provide NO₂^--N for ANAMMOX.Previous studies have usually used sodium acetate and glucose as carbon source in PD process,which causes high costs in practical application.In order to reduce the cost of nitrogen removal,brewery wastewater was utilized to test the viability of initiating PD and combining PD with ANAMMOX.In this study,the seeding sludge taken from the Brewery Plant sewage treatment station and PD reactor in the laboratory with acetate as carbon source were fed with brewery wastewater to start up PD.In addition,the NO₂^--N accumulation performance under different influent substrate concentrations was investigated during the long-term operation in PD systems.Furthermore,the integrated PD-ANAMMOX coupled process and the separated PD-ANAMMOX coupled process were set up to investigate the nitrogen removal performance with the brewery wastewater as carbon source.The main research results were as follows:（1）The wasted sludge taken from the brewery plant sewage treatment station was used as the seeding sludge and the brewery wastewater was adopted as carbon source in the PD processes,which were started up in winter and summer,respectively.The PD process,which initiated in winter,was successfully started up after 58 days of operation.At initial COD_Cr/NO₃^--N of 8.0 the mean NO₂^--N accumulation ratio（NAR）was 37.0%during the stable operation period.When the initial COD_Cr/NO₃^--N decreased to 5.0,the average NAR of 49.9%was obtained.Another PD process,which were initiated in summer,was successfully started up after 51 days of operation.During the stable operation period the the mean NAR of 61.5%was achieved at initial COD_Cr/NO₃^--N of5.0.Meanwhile,the PD sludge fed with sodium acetate in the laboratory was used as inoculated sludge in this study to start up PD process,replacing the carbon source with brewery wastewater.The PD process was successfully started up after 42 days of operation.At initial COD_Cr/NO₃^--N of 5.0,the mean NAR of 78.5%was obtained during the stable operation period.C/N ratio of about 4.5 contributed more to NO₂^--N accumulation in three PD systems.The dominant genus was Thauera in the PD systems with the relative abundance of above 60%.（2）As NO₃^--N concentration in the influent increased from 50 mg/L to 100 mg/L and 150 mg/L in PD processes,Thauera was still the dominant genus.By controlling the appropriate anoxic reaction time,the NAR in the PD system was approximately70%～80%.However,the denitrification rate was significantly reduced.And the sludge settleability became poor after increasing the influent NO₃^--N concentration.（3）The integrated PD-ANAMMOX coupled process was operated for 30 days with initial COD_Cr,NH₄⁺-N and NO₃^--N concentrations of about 60 mg/L,25 mg/L and 35mg/L,respectively.The denitrifying bacteria was gradually enriched in the system.The maximum NH₄⁺-N removal efficiency and TN removal efficiency of the integrated process were 95.4%and 79.6%,respectively.In the separated PD-ANAMMOX coupled process,the effluent of the PD reactor entered the ANAMMOX reactor to provide NO₂^--N.The separated PD-ANAMMOX coupled process was operated for 30 days with initial NH₄⁺-N and NO₂^--N concentrations of about 25 mg/L and 35 mg/L,respectively.And the average NH₄⁺-N and TN removal efficiency in the ANAMMOX reactor were95.2%and 82.5%,respectively.The maximum TN removal efficiency was 94.8%.The dominant genus was Candidatus＿Brocadia in both the integrated PD-ANAMMOX reactor and the ANAMMOX reactor of separated PD-ANAMMOX process,with the relative abundances of 55.3%and 31.5%,respectively.