Denitrification Research On High-ammonia Nitrogen Wastewater Treatment By The New Step-feed Cyclic A/O Process

A new kind of internal cycle multistage A/O process system is used in this experiment,there is an internal cycle between anoxic area and aerobic area of the same level,it makes cycle of part of the sewage inside anoxic area and aerobic area,increase the rate of denitrification.Simulating urban sewage is used as treatment object in this experiment,explore feasibility by efficient denitrification of the process on high ammonia nitrogen urban sewage.With the COD concentration of 211-459mg/L,ammonia concentration of 54-85 mg/L,total nitrogen concentration of 57-88mg/L,pH ranging from 7 to 8,this paper mainly focused on the influence of mixed reflux and HRT on the system performance?the formula change of water quality and system performance rate?including the rate of OUR?AUR and NUR?and the mean concludes as follows:?1?On the four kinds of operating condition about 50%?100%?150% and 200%internal reflux ratio,COD removal rate all remain at a higher level;ammonia removal rate decreases with the increase of the reflux ratio;influence on the removal rate of system by mixture internal reflux ratio is not large,COD and ammonia concentration of effluent is stable and satisfies A standards;average TN removal rate present a trend of decline after rising with the increase of mixture internal cycle,when internal reflux ratio was 50%,TN removal rate is only 73.20%,and the effluent TN is not reach standard,within the other three internal reflux ratio,the TN removal rate are all improved,but within the internal reflux ratio of 200%,the average effluent TN concentration is over 15 mg/L,also reduced the average removal rate.So,internal reflux ratio shall be controlled within a proper range.?2?Under the four different working conditions of HRT for about 8h?10h?12h and 14 h,the average COD removal rate does not change significantly as the increase of HRT,the effluent COD concentration is low,it can be controled under 50mg/L;when HRT is 8h,average ammonia removal rate was 87.28%,ammonia removal rate of the other three conditions were over 94%,removal rate kept on ahigher level,and effluent ammonia concentration is less than 5 mg/L,it is said that improve HRT within a certain range can improve the removal rate of ammonia;improve the HRT within a certain range can improve TN removal rate.?3?When average ammonia concentration is 75 mg/L ? C/N ratio is 4.5 of flooding water quality,TN removal rate can reach a high level within a certain mixture of reflux ratio and HRT range?such as mixture reflux ratio of 100%?150%,HRT of 10 h?12 h?14 h?,it proves that the new internal cycle multistage A/O process has obvious advantage on treatment of low C/N ratio of urban sewage.?4?By analyzing the performance about four kinds of internal reflux ratio and four kinds of HRT will affect on the system,found that large fluctuation of the water quality have little impact on the removal rate of system even have no influence,and the effluent water quality will have little change as the change of inflow water,this process system has strong resistance about shock loading.?5?Analyzed the change of water quality along the reactor on 100% of internal reflux ratio,10 h of HRT.DO?water temperature?pH of the reactor have little change,DO concentration of every anoxic area the DO concentration are all at low levels,the difference is not present,but the DO concentration in the aerobic area rises step by step,reduce air concentration step by step can be adopted during the experiment;with the high COD of inflow water,after the water get into anoxic area,COD concentration reduced more because of the dilution and sludge adsorption;the three of ammonia concentration of anoxic area is higher than aerobic area of the same level,the ammonia concentration of the three anoxic area were similar,the ammonia concentration of the three aerobic area were roughly equal,nitration efficiency is higher;even inflow TN concentration is high,after the water get into the anoxic area TN concentration will reduce much,the TN concentration of anoxic area is greater than aerobic area of the same level as the high ammonia concentration of inflow water;the NO₂^--N and NO₃^--N concentration of aerobic area were greater than anoxic area of the same level,high ammonia nitrogen sewage has conducted a part of shortcut nitrification and denitrification in the reactor,shortcut nitrification and denitrification model has formed,it is necessary for next studies;MLSS concentration in the system present the trend of decreasing step bystep,compared with traditional activated sludge process,average sludge concentration in the this process system has increased.?6?rates of OUR ?AUR and NUR of the new internal cycle multistage A/O process system was measured.OUR of second aerobic area is 35.85mgDO/?gMLSS · h?,AUR is 5.78 mg NH₄⁺-N/?gMLSS · h?,the largest NUR is 3.90mgNO₃^--N/?gMLSS ·h?,the three rate have influence with each other at a certain extent.