Design And Experimental Sudy Of Corridor Bioretention

Bioretention is an important engineering facility for sponge city construction,which plays an important role in reducing runoff and purifying rainwater.In order to improve the treatment effect of bioretention on the initial runoff and rainwater,the structure of traditional bioretention was improved according to the construction demand of Zhenjiang sponge city.The device of corridor bioretention was constructed and relevant research was carried out.The same scale of corridor bioretention and traditional bioretention devices were designed and constructed.On the basis of the study on the water quality characteristics of road runoff,the simulated runoff was configured,and the effect of the simulated runoff treatment was compared.The study was carried out under different influent intensity,pollution load,water intake time and dry period.Finally,the experimental study of runoff rainwater treatment in corridor bioretention was carried out.The main conclusions are as follows:?1?The structure of corridor bioretention device was designed.An impermeable membrane was laid inside the corridor bioretention to form a three-layer serpentine corridor.The length,width and height wer 1000 mm,400 mm and 1000 mm respectively.Three layers of corridors wer laid inside the corridor bioretention through plastic film.The planting soil layer was 200 mm,the packing layer 1,the packing layer2 and the packing layer 3 are all 150 mm,and the gravel drainage layer was 150 mm.?2?Water quality characteristics of road runoff rainwater was studied.In the early stage of the detection of runoff and rainwater,SS concentration reached 165⁵11 mg/L,COD concentration was 98³15 mg/L,NH4+-N concentration was 4.6¹2.4 mg/L,TP concentration was 0.4¹.96 mg/L,and NO₃^--N concentration was 2.3⁸.4 mg/L.?3?A comparwason on the effect of water collection time on pollutant removal was studies.The removal rate of COD and NH₄⁺-N was higher in the corridor bioretention,and the fluctuation rate of the removal rate was lower at different water collection time.The traditional bioretention has a good removal effect on TP,but the fluctuation of the two bioretentions were large at different water collection time.The removal rateof NO₃^--N in corridor bioretention was higher.The effluent concentration of NO₃^--N fluctuated greatly in the two bioretentions at different time.?4?A comparwason on the effect of influent intensity on pollutant removal was studied.The removal rates of COD in the corridor bioretention were 92.3%,83.1%and78.1%under the hydraulic loads corresponding to the three rainfall recurrence periods of 1a,2a and 5a.The removal rate of NH₄+-N were 96.1%,95.9%,and 93.7%.The removal rates of TP were 89.7%,86.5%,and 69.8%.The removal rates of NO₃^--N were56.1%,46.7%,35.1%.The removal rates of COD in the traditional bioretention were90.6%,76.1%and 71.4%under the hydraulic loads corresponding to the three rainfall recurrence periods of 1a,2a and 5a.The removal rate of NH₄⁺-N were 90.2%,92.5%,and 94.1%.The removal rates of TP were 85.7%,87.1%,and 86.6%.The removal rates of NO₃^--N were 52.3%,40.3%,38.0%.?5?A comparwason on pollutant removal effect in dry period was studied.After 5d,10 d,and 20 d drought periods,the COD concentration in the effluent of traditional bioretention was lower.Corridor bioretention has better recovery and processing capacity and lower fluctuation of effluent concentration.The 30 d drought period has a huge impact on the COD effluent of both bioretentions,especially the traditional bioretention.The drought periods of 5d,20 d and 30d have less impact on the capacity of corridor bioretention to process NH₄⁺-N.After the 10 d drought period,the traditional bioretention has better effect on treating NH₄⁺-N.In terms of treating NH₄⁺-N,the corridor bioretention was more adaptable to the changes in the dry period than the traditional bioretention,and it performs better during the alternation of wetting and drying period.The drought periods of 5 d,10 d and 30 d have less impact on the capacity of traditional bioretention to process TP.After the 20 d drought period,the corridor bioretention was almost unaffected.Throughout the wet and dry alternation period,the corridor bioretention treatment effect was better and more stable.After the 5 d,20 d,and 30 d drought periods,the corridor bioretention has a lower and more stable effluent concentration in the treatment of NO₃^--N.After the 10 d drought period,the effluent concentration of the corridor bioretention was higher.Throughout the wet and dry alternation period,the corridor bioretention treatment effect was better and more stable.?6?A comparwason on the effect of inlet pollution load on pollutant removal was studied.Corridor bioretention has better purification effect and stability under high load.The removal of TP was worse under low load.The average removal rates of COD,NH₄⁺-N,TP and NO₃^--N in corridor bioretention under high load were 91.4%,94.7%,90.4%and 38.3%respectively.The average removal rates of COD,NH₄⁺-N,TP and NO₃^--N in traditional bioretention under high load were 84.2%,91.9%,86.3%and 33.6%respectively.The average removal rates of COD,NH₄⁺-N,TP and NO₃^--N in corridor bioretention under low load were 84.9%,95.6%,85.9%and 48.0%respectively.The average removal rates of COD,NH₄⁺-N,TP and NO₃^--N in traditional bioretention under low load were 78.0%,91.0%,92.3%and 39.7%respectively.?7?The effect of corridor bioretention on the removal of runoff rainwater pollutants was studied.the average removal rates of COD,NH₄⁺-N,TP,NO₃^--N in the corridor bioretention were 76.5%,82.5%,64.0%and 33.9%,respectively.