Research On Removal Of Phosphorus In Rural Domestic Sewage By Conbined Process Of Bioligical Contact Oxidation And Adsorption

A large amount of untreated rural domestic sewage has become a potential threat to the water environment in China,especially the unremoved phosphorus which can easily cause eutrophication in rural water sources.Eutrophic water not only affects human production and life,but also may directly harm the human body.Therefore,it is necessary to enhance the treatment process of rural domestic sewage from the technical level,reduce the phosphorus content in the discharged rural domestic sewage through technical improvement,and reduce the eutrophication of water body.In this paper,on the basis of biological phosphorus removal,adsorption phosphorus removal and phosphorus removal from rural domestic sewage at home and abroad,the removal effect of biological contact oxidation-adsorption combined process on phosphorus removal from rural domestic sewage was investigated,aiming to fundamentally reduce the effect of phosphorus in rural domestic sewage on aquatic ecological environment.This study explores the biological contact oxidation-adsorption combination process on the rectification of phosphorus in rural domestic sewage.The results show that the process can remove phosphorus in rural sewage to less than 0.5 mg/L,reach the standard of"pollutant emission standards for urban sewage treatment plants"(GB18918-2002)level A standard,and have a certain anti-COD,NH4~+-N and TP shock load performance,specific research is as follows:First of all,five kinds of fillers,such as small ceramic(1-3 mm),large ceramic(5-8 mm),suspended packing,sponge packing and volcanic rock,were tested to find a kind of packing with short hanging time,high removal rate of COD and NH4~+-N and forming dense biofilm.The results show that the film forming process can be completed in about 17 days,and the removal rates of COD and NH4~+-N are above 96%and 70%respectively.Secondly,the optimal operation parameters of biological contact oxidation process were determined.The results show that when Hydraulic Retention Time(HRT)=10 h and reflux ratio is 100%,the effluent concentration of COD,NH4~+-N,TN and SS can reach the first class a standard in the discharge standard of pollutants for municipal wastewater treatment plant(GB18918-2002),while the effluent concentration of TP can not reach the first class B standard in the discharge standard of pollutants for municipal wastewater treatment plant(GB18918-2002).Then,the optimal preparation conditions of sludge based biochar(C-SBC)were determined by orthogonal experiment.Meanwhile,fly ash modified sludge carbon(F-SBC)and calcium oxide modified biochar(Ca O-SBC)were prepared by using fly ash and calcium oxide respectively,and their phosphorus removal performance was explored.The results showed that the optimal preparation conditions were carbon temperature 600℃,heating rate 22.5℃/min and carbon time 60 min.F-SBC and Ca O-SBC modified by sludge based biochar can effectively improve the phosphorus removal performance of C-SBC.The absorption of phosphorus by F-SBC and Ca O-SBC followed the Langmuir isotherm model and pseudo second order kinetics.The absorption of phosphorus on F-SBC and Ca O-SBC is spontaneous and endothermic.After four adsorption desorption cycles,the adsorption capacity retention of F-SBC and Ca O-SBC for phosphorus is more than 70%,and both of them have good regeneration performance.Finally,the combined process of biological contact oxidation and absorption was explored to remove phosphorus from rural domestic sewage.The results show that COD removal mainly depends on anaerobic zone,which accounts for 71%of the total COD removal.NH4~+-N removal rates in anaerobic zone and aerobic zone are almost the same,accounting for 49%and 44%of the total NH4~+-N removal respectively.TN removal mainly depends on anaerobic zone,which accounts for 59%of the total TN removal.TP is mainly removed in the aerobic zone,and its concentration is below 0.5 mg/L after absorption.The removal of SS mainly depends on the anaerobic tank.Under different COD,NH4~+-N and TP loads,it was found that the total phosphorus concentration in effluent was below 0.5 mg/L.Therefore,the biological contact oxidation-adsorption combination process has great development potential and development prospects in rural domestic sewage treatment.