Study On Separation Treatment Of Black Water And Grey Water And Optimization Of Denitrification Performance With Bio-Ecological Process

According to the quality and quantity of rural sewage,the black water and grey water were separately collected from the source.Combined with the existing bio-ecological technology,a combined process of“black water anaerobic–mixed sewage anoxic–aerobic–constructed wetland”was proposed.The small volume of black water was firstly treated in the medium temperature anaerobic baffled reactor,then the effluent mixed with the large volume of grey water into the anoxic reactor.The waterwheel dual-side-drive type rotating biological contactor was used for aerobic treatment with the advantages of energy-saving,land-saving and adequate oxygenation.Wherein,a part of the nitrification liquid was returned to the anoxic reactor for the purpose of denitrification and deodorization.The following constructed wetland was used to ensure the effective removal of nitrogen and phosphorus.In this study,the waterwheel type rotating biological contactor was improved,and the“anoxic-aerobic”stage was maily studied.The main results are as followed:?1?The removal of COD and nitrogen in the anoxic reactor was greatly affected by reflux ratio.It was suggested that the reflux ratio was 100%-150%in summer or autumn,while the removal rate of COD and TN were 62.82%-65.26%and 36.46%-44.86%,respectively.It was suggested that the reflux ratio was 150%-200%in winter or spring,while the removal rate of COD and TN were 56.14%-59.16%and 28.89%-25.75%,respectively.Furthermore,the hydraulic retention time?HRT?had a great effect on the removal of nitrogen in the anoxic reactor,so the HRT was suggested to be 6.4 h in summer or autumn and 8.0 h in winter or spring,respectively.?2?The HRT of the waterwheel dual-side-drive type rotating biological contactor had a significant effect on the removal of COD and NH₄⁺-N.It was recommended that the HRT was 3.0 h in summer or autumn and 4.5 h in winter or spring,respectively.The Oxygenation efficiency of the rotating biological contactor decreased with the continuous increase of reflux ratio,which in turn reduced the removal rate of NH₄⁺-N.So the reflux ratio of 100%was recommended in summer or autumn and 150%in winter or spring,and the corresponding removal rate of NH₄⁺-N were 91.35%and 69.80%.In addition,the rotating speed had a significant effect on the removal rate of COD and NH₄⁺-N.It was recommended that the rotating speed was 4.0 r/min-5.5 r/min in summer or autumn,when the removal rate of COD was more than 85%,the removal rate of NH₄⁺-N was about 90%.In winter or pring,after improving the device,the acceleration of the rotating speed shortened the HRT of the waterwheel driving area.Therefore,it was recommended that the rotating speed was reduced to 4.0 r/min,resulting in the COD removal rate of 80.88%and the NH₄⁺-N removal rate of76.33%.The overall TN removal efficiency of the rotating biological contactor was limited,less than 20%.?3?According to the clear water test,the results found that the rotation and the oxygenation capability of the rotating biological contactor were superior and basically no water splashing,when driving water dropping height was 0.4 m,driving flow was 130ml/min-630 ml/min,water distribution height was 0.6 m,water distribution flow was 360ml/min-450 ml/min.?4?When the C/N ratio of influent was constant,the NO₃^--N/TN ratio of the anoxic influent had a certain effect on the denitrification.The NO₃^--N/TN ratio of about 0.3 was suggested in summer or autumn and about 0.25 in winter or spring,due to the better nitrogen removal efficiency.?5?Under the recommended condition,the average removal rate of COD,TN and NH₄⁺-N in the“anoxic-aerobic”stage were 79.82%,45.99%and 94.83%in summer or autumn,respectively.In winter or spring,after improving the device,the average removal rate of COD,TN and NH₄⁺-N in the“anoxic-aerobic”stage were 78.23%,33.03%and79.84%,respectively,having lower removal rate than summer or autumn.In general,the effluent COD and NH₄⁺-N could stably satisfy the class A emission standard in the“pollutant discharge standard of urban sewage treatment plant"?GB 18918-2002?,while TN and TP need to be further removed in the subsequent constructed wetland.The waterwheel dual-side-drive type rotating biological contactor had an excellent impact resistance,and the operation effect and membrane growth could be returned to normal within 4 d-15 d after the power failure and pipeline damage.