Experimental Research On Treatment Of Urban Sewage With Multi-stage A/O+Double Packing Filter

In recent years,the state's control over the upgrading and reform of sewage treatment and related policies have promoted the continuous innovation of various sewage treatment processes,and the situation of eutrophication of water bodies has been relatively improved.However,it is difficult to reach the first-level A water discharge standard by relying on a single biochemical system alone.The multi-stage A/O process is concerned because of its strong impact load and the ability to reasonably distribute the demand for organic matter in the process of denitrification and dephosphorization at multiple points of water entry.However,due to the different competitiveness of sludgeretention time(SRT)and carbon source,the TP effluent is still difficult to achieve the desired effect,so the dual-filler filter system is added to deeply treat the effluent of the A/O system,and the nitrification of the entire system is achieved under controlled conditions,thereby reducing energy consumption.In this project,a three-stage A/O+dualfiller system is used to increase nitrification,denitrification,and denitrification under the condition of adding a pre-hypoxic section to promote effective phosphorus release and the synthesis of an internal carbon source(PHB)dephosphorization reaction.In the later stage,mixed sludge is added to control the DO concentration of each reaction cell to promote the balance between the two biochemical processes of ammonia oxidizing bacteria(AOB)and nitrosating denitrifying phosphorus phosphate bacteria(DNPAOs).Under the premise of deep nitrogen and phosphorus removal.This experiment isbased on the premise that no nitrate liquid reflux is set up.By studying the impact of HRT,double-point influent and three-point influent on the removal of pollutants in the system,and using the mathematical analysis method to compare the treatment effects,each oxygen limitation is gradually reduced.To achieve partial nitrification and nitrification denitrification and phosphorus removal in the multi-stage A/O system,the whole system obtained the following results:(1)The starting temperature of multi-stage A/O is 20?26?,and the volume ratio of pre-hypoxia/hypoxia/aerobic is 1:6:3.when HRT of hypoxia section is 5.4 h,COD effluent concentration is 36.8 mg·L-1.The contribution rate of effluent concentration of NO3--N to the removal of TN is less than 50%,the multi-stage A/O system wassuccessfully started.A small-scale adsorption performance test was performed to study the effect of the in-depth treatment of dualfiller system.The maximum and minimum equilibrium adsorption amounts for COD under four different water gradients were 4.85 mg·L-1 and 0.97 mg·L-1.The R2 value of the correlation coefficient y=0.23x ± 4.72 is 0.93,which is in line with the linear law of the Langmuir adsorption model.The total adsorption of NO3--N is reduced by the influent C/N ratio from 10.8%to 5.4%,Basically Maintains the advanced processing function of double packing.The content of each part is to compare the water output effect under the 4 working conditions.It is found that the removal of COD is closely related to the presence or absence of the addition of a pre-hypoxic section,and run2,run3,and run4 are significantly better than runl.When V pre-hypoxia:V hypoxia:V aerobic=1:6:3,nitrifying bacteria and denitrifying bacteria can make better use of carbon source to denitrify,denitrify and dephosphorize.During the start-up of the dual-filler system,in order to stimulate and enrich the predominant strains that can consume refractory organic matter in the biofilm of the filler system under the change of the water inlet load,setting 4 water inlet gradients still ensures the stability of the system under low organic load Out of water.(2)After the combined system was started,because the system's single-point underwater denitrification and phosphorus removal effect is relatively unstable,the A2/O-BAF system with the same total pool capacity and total HRT is added for data analysis and comparison.When the HRT is 8h,the influent COD,NH4+-N,TN and TP concentration is 187.1,61.2,70.5,5.9 mg·L-1,the COD,NH4+-N,TN and TP of the effluent of both systems can reach the the first class dischargestandard(GB 18918-2002);The averageTN andTP effluent concentrations of the A2/O-BAF system is 13.4 mg·L-1 and 0.38mg·L-1,which is better than the multi-stage A/O+double-filled filter system21.2 mg·L-1 and 1.33 mg·L-1;adding COD material balance of each section of the two systems,the carbon source utilization effect in the process of refined nitrogen removal shows that the total effective utilization rate of the carbon source entering the anoxic section of the A2/O-BAF system is 46.5%,higher than 31.0%of the multi-stage A/O+double-filled filter system.The content of each stage includes:When the HRT is reduced from 9h to 6h,the A2/O-BAF system guarantees that the overall effluent is less than 5 mg·L-1 after 80%and 15%of the NH4+-N removal contribution rate of the combined stage is guaranteed.Effect,but TN removal deteriorates.The multi-stage A/O+double-filled filter system ensures that the single-stage A/O section effective carbon source utilization rate is 31%,and the NH4+-N removal rate is guaranteed to be above 86%but the effluent TN effect is not good.In the TP removal effect,the optimal effluent concentration of the A2/O-BAF system is 0.33 mg·L-1,which is better than the 1.33 mg·L-1 of the multi-stage A/O+double-filled filter system.The total removal of HRT on the A2/O-BAF system The effect of phosphorus effect is more than the multi-stage A/O+double-filler filter system process.In order to study the denitrification and phosphorus removal characteristics using NO3--N as the electron acceptor,linearly fitting the changes of the ?PO43-and ?NO3--N in the hypoxic section of the two systems,and found that the linear correlation is small(R2<0.7),considering the normal distribution of the probability density of denitrifying phosphorus removal by mathematical analysis,the results show that when the optimal HRT is 8h,the denitrification probability density ?PO43-/?NO3--N of A2/O-BAF system and multi-stage A/O+doublefilled filter system are 1.21 and 0.95,the A2/O-BAF system is closer to the theoretical value of 1.41,and the denitrifying phosphorus and nitrogen removal effect is better.(3)When the two-point influent ratio is 2.5:1,and the average influent COD,NH4+-N,TN,and TP concentrations are 281.5,65.7,75.3,and 7.3 mg·L-1,the average effluent concentration is 21.5,3.0,16.0,0.8 mg·L-1,the proportion of denitrifying bacteria(DPAOs)in the hypoxic segment to PAOs was 68.0%,and the proportion of denitrifying phosphorus removal density(?PO43-/?NO3--N)was 1.21,cumulative frequency 45%;Continued to increase the ratio of influent water was to 3:1 and 2:1,the density of denitrifying polyphosphate bacteria decreased,and the sludge activity f(MLVSS/MLSS)decreased from 0.71 to 0.55.The sludge output increased with the increase of the total influent water.(4)When the three-point influent ratio is controlled to be 6:3:1,5:3:2,and 5:2:3,because of the existence of the dualfiller system,the efficient oxidation of NH4+-N and the removal of COD can be achieved.To achieve partial nitrosation in a continuous stream,set three points of optimal water inflow ratio of 5:3:2,combine the domesticated mature ammonia oxidizing bacteria(AOB)and nitrosating denitrifying phosphorus removal bacteria(DNPAOs)sludge into the multi-level A/O system in equal proportions.When controlling the DO concentration of each oxygen limit to be 0.3?0.5,1.2?1.5,1.0?1.2mg·L-1,and the sludge return ratio(R)is 100%,the system achieves partial nitrification and nitrification denitrification phosphorus removal Balance,the ammonia oxidation rate(ARE)reaches a maximum of 81.4%.Nitrous accumulation rate(NiAR)can reach the highest values of 23.0 mg·L-1 and 81.1%,multi-stage A/O and system total TP effluent reaches about 1.05mg·L-1 and 0.5mg·L-1,achieving stable partial nitrosation and nitrosation and denitrification removal of phosphorus and nitrogen.The specific effluent effect is that by adjusting the three-point influent ratio to 5:3:2,the multi-stage A/O+ double filler system can ensure good nitrogen and phosphorus removal effects.When the influent COD,NH4+-N,TN,TP concentration When the average is 291.8,69.3,71.6,and 6.9 mg·L-1,the effluent concentration is 17.6,5.7,14.9,and 0.49 mg·L-1,respectively,and the effluent basically meets the "Emission Standard of Pollutants for Urban Wastewater Treatment Plants"(GB18918-2002)Grade A standard.When the optimal influent ratio is 5:3:2,the effluent effect when the DO concentration of the four oxygen-limiting grids is at stage ?(each DO concentration is 0.3?0.5,1.2?1.5,1.0?1.2mg·L-1)The best,the average concentration of effluent COD,NH4+-N,TN,TP is 20.9,5.9,17.6,0.49mg·L-1.At this stage,the partial reaction process of nitrification and nitrification denitrification and phosphorus removal maintains a balance.The NO2--N concentration and NiAR reached the maximum,and their values were 81.4%,23.02mg·L-1 and 81.1%.