| In this study,a new type of double sludge denitrification and denitrification and dephosphorization process—A2/O-biological contact oxidation(BCO)was used to realize that both nitrifying bacteria and phosphorus accumulating bacteria can grow under their own favorable conditions.The BCO packing adopts polypropylene suspension packing,and the series connection of N1,N2,and N3 can efficiently realize the nitrification reaction and provide sufficient nitrogen source for A2/O.In this experiment,low C/N ratio sewage was used to complete the start-up and subsequent stable operation of the reactor.Through a long-term batch test,the influence of nitrification liquid reflux ratio,hydraulic retention time and other factors on denitrification nitrogen and phosphorus removal effect was explored,and the test excess sludge was deeply dehydrated,and its dewatering performance was analyzed and the available resources were recycled.The main research contents and related conclusions are as follows:(1)The BCO reactor adopts the natural film-hanging method to basically complete the film-hanging in about 30 days.With the completion of the film formation,the thickness and color of the N1,N2,and N3 biofilms are different,and with different nitrous accumulation effects,the thickest N2 biofilm is 220μm.At the same time,the A2/O reactor at the start-up stage The simultaneous removal of COD and NP can be achieved.The removal rate of COD is above 90%,the removal rate of TN is 70%-75%,and the removal rate of TP can reach 80%.(2)On the basis of stable operation,the nitrification liquid reflux ratio was changed to explore the effect of pollutants removal in the reactor under different nitrification liquid reflux ratios.The A2/O-BCO system successfully optimized the nitrate reflux ratio.Treated low C/N ratio wastewater,and proved that R=300%-400%is the watershed for pollutant removal.The experiment shows that the total removal rate of COD is 85.66%-88.79%by the reflux ratio of the nitrification solution,and the overall effect is not significant,which further shows that the phosphorus release has a strong correlation with the influent COD.In addition,the characteristics and changing laws of the pollutants indicate the role of the aerobic zone in stabilizing the phosphorus in the effluent and the role of the hypoxic zone on the accumulation of NO2--N.(3)In addition to the backflow of nitrification liquid,continue to investigate the impact of hydraulic retention time(HRT)on the treatment of pollutants in the A2/O-BCO system.The removal rate of COD is above 80%,and the removal rate of TN is 80%.After aerobic TP The removal rate can reach 90%.With the difference of HRT,when HRT=8h,the sludge can be more granulated(D50:265.6μm;SVI5/SVI30:1.1-1.3),although MLVSS dropped from 2630 mg/L(12 h)to 2294(10 h),2090mg/L(8h),but the sludge particle distribution is still further compared.On the 50th day,the particle size larger than 200μm was only 2.36%,mainly smaller than 50μm and 50-100μm(65.61%,21.29%).At 10h(120th day)and 8h(185th day)of HRT,the particle size of activated sludge is larger than 200μm,18.64%(18.05%±0.59%)and 25.60%(24.11%±1.49%).The proportions are 37.63%and 23.30%respectively.(4)Finally,a deep dehydration test was carried out on the remaining sludge produced in the test.In this test,activated potassium persulfate showed good conditioning performance.After activated potassium persulfate conditioning,the sludge dehydration performance has been greatly improved.Among them,the sludge specific resistance reduction rate can reach up to 90%,and the moisture content can be reduced to below 65%.At the same time,the sludge dehydration process can release a large amount of phosphorus resources.In the experiment,it can release 32mg/L to obtain phosphorus after conditioning by activated potassium persulfate,and to a certain extent,it increases with the increase of temperature and oxidant dosage,and the released nitrogen and phosphorus can be Synthesize struvite,hydroxyphosphate and other phosphorus-containing resources. |
PDF Full Text Request