不同改良介质土对生物滞留系统运行性能的影响

The Effect of the Modified Soil Media on the Performance of the Bioretention System

生物滞留系统运行性能受填料层的介质土特性显著影响。为规范填料层介质土级配方式,提高重庆城区生物滞留设施建设水平,结合重庆城区土壤本底调查结果,将壤砂土和细砂,砂土和细砂分别以1∶9和2∶8(质量比)混合形成2类传统生物滞留介质土(BSM1和BSM2)。在此基础上分别添加不同质量比的蛭石(Ver.)、生物炭(BC)、珍珠岩(Per.)作为改良剂形成6种改良介质土,并考察不同介质土下生物滞留系统水力性能和除污特性。结果表明,不同介质土具有不同的初始水力渗透系数和衰减性能,其中BSM2+8%Ver.介质土的水力渗透性能最稳定(渗透系数为41~53 mm/h),而BSM1+2%BC介质土水力渗透性能衰减最快。所有介质土均可有效去除径流污染物,尤其是可高效去除径流中的悬浮物(SS),出水浊度可达到10~16 NTU;BSM1及其改良组对有机物和营养物的去除能力较BSM2及其改良组强。利用投影寻踪法综合考虑介质土除污能力、水力渗透性能、填料价格等因素,确定不同改良介质土得分的综合排序依次为:BSM1+2%Ver.(0.60)>BSM1(0.52)>BSM1+2%BC(0.41)>BSM1+2%Per.(0.40)>BSM2+8%Ver.(0.33)>BSM2+8%BC(0.23)>BSM2(0.15)>BSM2+8%Per.(0.14)。

The performance of the bioretention system is significantly affected by the soil media characteristics.In order to standardize the gradation of packing soil media and then improve the construction level of bioretention facilities in Chongqing urban area,two types of traditional bioretention soil media(BSM1 and BSM2)are mixed with loamy sand and fine sand in a mass ratio of 1∶9,and sandy soil and fine sand in a mass ratio of 2∶8,respectively,combining the results of the soil background survey in Chongqing.And on this basis,vermiculite(Ver.),biochar(BC)and perlite(Per.)are added as modifiers into BSM1 and BSM2 in different mass ratios,which finally configurates 6 types of modified soil media.Furthermore,the hydraulic permeability and pollutants removal performance of bioretention system with different soil media are investigated.Results show that different soil media shows different initial hydraulic permeability coefficient and attenuation performance,among which,the hydraulic permeability of BSM2+8%Ver.soil medium changes in a stable range of 41~53 mm/h,while the permeability of BSM2+8%BC soil medium has the highest attenuated rate.All soil media show an effective removal performance in runoff pollutants,especially in suspended solids(SS),and the effluent turbidity can reach 10~16 NTU.The removal capacity of the bioretention columns packed with BSM1 and its modified groups in organic pollutants and nutrients are superior to the other columns.Finally,this paper considers the factors of soil medium decontamination capacity,hydraulic permeability and price,the comprehensive ranking of modified soil media using the projection pursuit method:BSM1+2%Ver.(0.60)>BSM1(0.52)>BSM1+2%BC(0.41)>BSM1+2%Per.(0.40)>BSM2+8%Ver.(0.33)>BSM2+8%BC(0.23)>BSM2(0.15)>BSM2+8%Per.(0.14).