Experimental Study On Advanced Treatment Of Urban Sewage By Expanded Bed Denitrification And Dephosphorization Biofilter

In the thesis,to remove nitrogen and phosphorus in secondary effluent of urban sewage,expended bed biological filter process was reinvented from normal biological filter.The filter united the removal of nitrogen,phosphorus,SS in one device.In the filter,we first used irregularly shaped suspended filter material which is larger specific surface,more roughly and flexibly.It is studied the removal consequences of nitrogen and phosphorus which was treated by expended bed biological filter.Then providing useful databases for the third construction of the plant.First of all,the experiment was studied on the biofilm culturing feature of expended bed biological filter process.Secondly the removal of pollutants during normal functioning was investigated.Thirdly,making a research on the dosage of PAC when Phosphorus was removed.Then determined the backwashing method.Finally studying the factors which may influence the removal of nitrogen and phosphorus in expended bed biological filter process.The results were listed.?1?A natural biofilm startup was set for expended bed biological filter.The effluent concentration of COD was lower than 30 mg/L,removal rate was 74.32%,while TN was almost 10 mg/L and 50%.When concentration of TN was lifted from 5mg/L to 20mg/L,the filter could be recovered in 8 hours.?2?The filter fits a two-day backwash cycle,with 10mins of 8 in gas backwash and 4 in water wash.?3?Removal of phosphorus was achieved by 10mg/L PAC at least,which corresponded to“urban sewage treatment plant pollutants discharge standard?GB18918-2002?”A in the first grade.The concentrations of TP and SS are 0.384mg/L,9.67mg/L.?4?With the increasing influent hydraulic load,both concentrations of COD and TN were lifted first and dropped lastly,TP had no much changes.The best influent hydraulic load was 8 m³/?m²·h?.Under these four circumstances of C/N,the C/N of 2.5:1 is the best condition among them.?5?Under the best condition,influent hydraulic load was 8 m³/?m²·h?and the C/N of2.5:1,the effluent quality?means values?reached to:COD_Cr=24.11mg/L,TN=12.15mg/L,TP=0.42 mg/L,SS=8.44mg/L.