Optimization Of Control Parameters For Integrated DN-PN-ANAMMOX Combined Process

Anaerobic ammonium oxidation?ANAMMOX?has great advantages in treating ammonia-containing wastewater with low organic carbon sources.However,some of the nitrates produced by the reaction are very serious in the treatment of high ammonia wastewater,and the total nitrogen in the effluent may not meet the discharge standard.As a traditional denitrification process,denitrification combined with anaerobic ammonium oxidation will improve the overall removal rate.At present,there are many kinds of joint forms in domestic and foreign research reports,which can be divided into one-stage and multi-stage,in one-stage reactor,it is difficult to obtain a higher nitrate removal rate at the same time of higher load because of the competitive relationship between various factors and substrate in the same reactor.In the multi-stage reactor,each reaction runs separately,and the functional microorganisms have a suitable growth environment,but the overall load level of the multi-stage combined process is not high,or even lower than the one-stage combined process.The reason is that the multi-stage process is often used in the treatment of practical wastewater,and there are other influencing factors.According to the setup of denitrification zone,the multi-stage process can be divided into two forms:post-denitrification and pre-denitrification.for most wastewater,there will be some organic carbon sources.pre-denitrification can make full use of organic carbon sources in raw water.At the same time,the influence of organic carbon source on the subsequent process was reduced.Therefore,a new type of integrated DN-PN-ANAMMOX combined process system is adopted in this paper.the denitrification zone is prepositioned and set the effluent reflux.suspended bio-packing system is used in the denitrification zone and aerobic zone,and anaerobic ammonium oxidation granular sludge system is used in the anaerobic zone.The effects of nitrate loading,filling ratio,reflux ratio and C/N ratio on denitrification performance in denitrification zone during start-up were investigated,and some control parameters were optimized to provide reference for their application.The main conclusions are as follows:?1?Control influent NH₄⁺-N concentration:400mg·L^-1,pH:8.0,aerobic zone DO:0.5mg·L^-1,temperature:35?,nitrateloadingNLR_an:0.47kg·?m³·d?^-1of denitrification zone,filling ratio:30%,C/N:0.125,reflux ratio:7,successfully started the integrated DN-PN-ANAMMOX process,the whole NRR is 1.45kg·?m³·d?^-1?HRT:6.2h?,NH₄⁺-N removal rate can reach 91%,TN removal rate can reach 87.8%,NO₃^--N removal rate can reach 83%,the 94.8%of NO₃^--N removal rate that the reactor can achieve under the reflux ratio.?2?High reflux ratio may affect TOC removal in denitrifying zone during the load lifting process,when the influent NH₄⁺-N concentration is 400mg·L^-1.The suitable reflux ratio is about 7,and the rising velocity of anaerobic zone is 7.9m/h.?3?The concentration of NH₄⁺-N in influent 400 mg·L^-1,the nitrate loading in denitrification zone NLR_an:0.47kg·?m³·d?^-11 and the filling ratio 30%were controlled,and the stable removal of TOC was realized.At the same time,the removal rate of NO₃^--N in the reactor can be improved by adding a little excess TOC?C/N:0.125?.In the process of increasing NH₄⁺-N concentration and reflux ratio,the nitrate load in denitrification zone should be reduced,and the C/N ratio of influent is close to 0.1,which can realize simultaneous removal of NO₃^--N and TOC in denitrification zone.?3?The influent NH₄⁺-N concentration 800mg·L^-1,reflux ratio about 14,control denitrification zone nitrate load NLRan:0.32kg·?m³·d?^-1,C/N ratio was 0.1,The overall NRR can be maintained at 1.27kg·?m³·d?^-1?HRT:15h?.the removal rate of TN,NH₄⁺-N and NO₃^--N can up to 97.1%,98.2%and 90%,the 96.4%of NO₃^--N removal rate that the reactor can achieve under this reflux ratio.