Study On The Effective Removal Of Nitrogen And Phosphorus In Urban Black-odorous Water By New Oxygen-carrying Adsorbent And Its Mechanism

Black-odorous water are ubiquitous in global urban rivers,mainly caused by hypoxia and nitrogen and phosphorus overload,and hypoxia is the key cause of continuous deterioration of water quality in urban polluted rivers.Hypoxia enhances the activity of reducing bacteria in surface sediments,promotes the formation of low-valent metals such as iron and manganese,and releases iron-manganese-bound phosphorus into water,causing continuous pollution.The traditional aeration technology has insufficient pertinence to the interface and severely disturbs the water.The surface layer of the sediment is easy to diffuse into the water through resuspension,causing secondary pollution.This paper uses two ways to load oxygen.Oxygen nanobubbles were loaded onto the surface of bentonite,attapulgite and muscovite minerals by alcohol-water substitution method.Oxygen was loaded into porous activated carbon,lanthanum（La）modified attapulgite,La modified Phoslock and muscovite by vacuum-pressure method.The effects of aeration and removal of phosphate,ammonia nitrogen and total nitrogen in black-odorous water were investigated.The results showed that the addition of oxygenated nanobubbles modified mineral materials in the alcohol-water replacement method increased the dissolved oxygen content at the sediment-water interface rapidly,up to more than 7 mg/L^-1,and the 1 cm surface layer of the sediment was transformed into an aerobic state.Compared with the control group,the total phosphorus content in the overlying water of the core in the experimental group decreased by more than 90%,inhibited the formation of sulfate reduction and reduced S^2-,and increased the ability of sediment iron oxide to fix phosphate.16S r RNA analysis showed that the addition of oxygen nanobubbles modified mineral materials inhibited the growth of Longilinea and Syntrophomonas in surface sediments,promoted the enrichment of Thermomonas,and the changes of microbial community showed the improvement of benthic living environment.In the vacuum-pressure swing method experiment,the addition of oxygen-loaded coal columnar activated carbon（OCC）or oxygen-loaded muscovite（OM）alone could increase the dissolved oxygen（DO）concentration at the sediment-water interface to more than6 mg/L^-1 on the first day,and OCC could maintain a high redox potential（ORP）（up to+327 m V）for 15 days.Most of the oxygen-carrying adsorbents significantly reduced the phosphate in water from 0.27 mg/L to<0.05 mg/L.In addition,by adding oxygen-carrying materials,ammonia nitrogen and total nitrogen were reduced by more than 50%.The results of 16S r RNA showed that Dechloromonas was dominant in abundance,and the reduction of nitrogen was mainly affected by microbial activity.Oxygen-carrying materials can rapidly improve the oxygen content at the sediment-water interface and effectively inhibit the release of sediment phosphorus,which has a good application prospect in the improvement of urban river water quality and in-situ control of endogenous pollution.