Experimental Study On The Treatment Of Community Rainfall Runoff By Matrix Modified Bioretention

Bioretention was a low impact development(LID)one of the core technology,mainly through physical,chemical and biological effects of combined pollution in water purification material,the SS,heavy metals,oil and microbial virus had better purification effect on nitrogen and phosphorus removal.In view of the traditional bioretention technology in nitrogen and phosphorus removal are poor removal effect,large fluctuations,unstable running problems,firstly,through the matrix optimization of matrix experimental study on adsorption characteristics of nitrogen and phosphorus by removal of phosphorus,ammonia nitrogen,on the basis of green building area road water quality for reference,through soil column simulation experiment studied the different structure of matrix modified bioretention system in different rainfall return period of each pollutant in rainwater removal.The main conclusions were as follows:(1)The results of adsorption characteristics of nitrogen and phosphorus on the substrate of the bioretention were showed that: 1)several matrix in phosphorus adsorption desorption dynamic balance process,in addition to sponge iron was relatively stable,the matrix adsorption equilibrium fluctuations,Phosphorus adsorption capacity from large to small followed by: sponge iron > limestone > ceramsite > coarse> gravel.Ammonia nitrogen adsorption capacity from large to small followed by: sponge iron > limestone > Coarse Sand > ceramsite > gravel 2)The isothermal adsorption curves of five substrates for phosphorus and ammonia nitrogen can be described by the Freundlich adsorption equation.The adsorption of phosphorus and ammonia nitrogen by sponge iron in the five matrices is the best,higher than that of other matrixes.3)With sponge iron as matrix,will compete for the adsorption of ammonia nitrogen and phosphorus matrix coexist,the presence of ammonia,the adsorption capacity of phosphorus by sponge iron;low concentration,the adsorption effect of ammonia is very small,with the increase of equilibrium concentration,its influence gradually increased.(2)Study on the removal efficiency of runoff pollutants by modified bioretention under different rainfall return periods were show that: 1)with different structure bioretention removal effect of COD,TP,NH4+-N,NO3--N,TN were affected by rainfall intensity the larger,while the removal efficiency of SS is affected by rainfall intensity is smaller.2)In comparison,when the rainfall return period was 2 years and 5 years,the removal rate of COD,NO3--N and TN was larger than that of the bioretention unit.The removal rates of COD in 1#,2# and 3# were 77.21%?82.2% and 67.43% respectively.The removal rates of NO3--N was 53.61%,67.75% and 40.61% respectively.The removal rates of TN was 60.25%,83.08% and 44.37% respectively.3)When the rainfall return period was 0.5 years and 1 years,the removal effects of SS,TP and NH4+-N were better.The removal rates of SS were 77.38%,74.32% and 67.43% respectively.The removal rates of TP were 85.04%,69.97% and 50.15% respectively.The removal rates of NH4+-N were 79.87%,74.70% and 57.22% respectively.Overall,1#,2# bioretention unit effluent quality stable met the Level ? of the Surface Water Quality Standards(GB3838-2002),the average quality met the standard IV,3# bioretention unit effluent water quality is poor,only some indicators can meet surface water standard V.(3)Compare of the 3 different structure of bioretention of runoff pollutants removal effect were show that : 1)the different structure of bioretention on the removal of SS pollutants has little effect;change the type of matrix,set the anaerobic submerged area can alleviate the effects of rainfall intensity on removal effect.2)When the rainfall return period is less than or equal to two years,the replacement of the improved matrix is more significant;when the rainfall recurrence period is relatively large,for 5 years and 10 years,the effect of the submerged area is more significant.3)Set the flooded area is conducive to the removal of NO3--N and TN,a very small influence on SS removal,but not conducive to the removal of TP and NH4+-N.The biological retention system has the characteristics of easy construction and simple maintenance,and is recommended for use in buildings and communities.