Experimental Study On In Situ Remediation Of Nitrogen And Phosphorus Pollution In Urban Rivers By Immobilized Biological Sponge

With the accelerating urbanization process,the pollution of inland river waters has increased.The in-situ treatment of water bodies has always played an important role in effectively treating urban polluted waters in the cities and rivers.The emerging sponge iron fillers are in constructed wetlands and urban water bodies.,It has received extensive attention in the field of advanced treatment,but it has rarely been reported as a filler for in-situ remediation of polluted water bodies in the urban rivers.In order to study the effect of immobilized biological sponge iron in situ remediation technology on the removal of nitrogen and phosphorus pollution in urban rivers,a river in the Dongjiang tributary of Huangpu District,Guangzhou City,Guangdong Province was used as the research object,and the inter-gravel contact oxidation reactor was used as the in situ remediation technology.For the immobilization of biological sponge iron,the symmetry experiment of sponge iron was carried out by SEM,EDS and XRD techniques.The static test of nitrogen and phosphorus removal by immobilized biological sponge iron was carried out with the dosage and pH as the influencing factors.The effect of residence time on the removal of nitrogen and phosphorus from the contact oxidation reactor between immobilized biological sponges.The results show as follows:?1?The main constituent components of sponge iron selected in the experiment were Fe,Fe₂CO₃,Fe₃C,Fe₂O₃ and Fe₃O₄,and the proportion of Fe element reached 85.0%.The sponge iron filler has a rough surface and is loose and porous,and has a sponge-like three-dimensional surface structure,which is an ideal biological carrier filler.?2?The static test of nitrogen and phosphorus pollution by immobilized biological sponge iron showed that the immobilized biological sponge iron had higher removal effect on total phosphorus than ammonia nitrogen.Under the condition of initial phosphorus concentration of 0.1,1,5,10,30,50 mg/L,the adsorption amount of phosphorus by immobilized biological sponge iron decreased with the increase of dosage,and the removal rate increased gradually.When the dosage is constant,the adsorption amount of phosphorus by immobilized biological sponge iron increases with the initial concentration of phosphorus,and the removal rate decreases.When the initial concentration of phosphorus solution was 10 mg/L,the removal rate gradually stabilized with the increase of dosage,indicating that the maximum removal rate of adsorption was99.30%.The optimal dosage of immobilized biological sponge iron is 2 g/L.The pH was changed under the optimal dosage,and the removal rate of different phosphorus concentrations gradually decreased with the gradual increase of pH.The unit adsorption amount tends to be stable during the pH increase process,but the alkaline condition is not conducive to the removal and degradation of phosphorus by the immobilized biological sponge iron,and the acidic condition is not conducive to the growth and reproduction of the microorganism.Therefore,the immobilized biological sponge iron should be kept in the neutral condition when polluted water has treated.When the initial concentration of ammonia nitrogen is 10,20 mg/L,and the dosage of immobilized biological sponge iron is 1,2,4 g/L,the dosage of immobilized biological sponge iron increases,which is lower.The removal rate and adsorption amount of ammonia nitrogen in the concentration gradually increased,while the removal rate and adsorption amount of ammonia nitrogen in the higher concentration gradually decreased.The dosage of immobilized biological sponge iron had a great influence on the adsorption and degradation of ammonia nitrogen.The removal of ammonia nitrogen increased within 24 h as the dosage increased.When the dosage of immobilized biological sponge iron was 10 g/L,the removal rate and adsorption amount at different initial concentrations of ammonia nitrogen showed a slow upward trend with the increase of pH.Under alkaline conditions,the immobilized biological sponge iron has a high removal effect on ammonia nitrogen.?3?The overall degradation effects of TP,TN and NH₃-N was better under the conditions of hydraulic retention time of 24h,12h and 6h respectively.When the hydraulic retention time was 24h,the immobilized biological sponge and iron and gravel contact oxidation device was used for ammonia nitrogen.Total phosphorus total nitrogen has a high removal rate.After shortening the hydraulic retention time by 12 hours,although the effluent water quality fluctuated within 20 days of operation,the effluent quality still reached the standard after continuous operation.When the hydraulic retention time is 6h,the final removal rate of total nitrogen is lower than the hydraulic retention time of 12h,but the inter-brick contact oxidation device still maintains a high total phosphorus and ammonia nitrogen removal rate and a residence time of 12h.Flat,stable waterafter stabilization.The immobilized biological sponge and iron-gravel contact oxidation device has a good treatment effect on nitrogen and phosphorus pollution in urban rivers,and provides a new method for the application of biological sponge iron,which provides a new idea for the in-situ treatment of urban river water pollution.Figure 41,table 6,reference 89...