| As an important part of urban catchment surface,urban roads are one of the main sources of non-point source pollution of water bodies.In the process of urban road rainfall in mountainous areas,the road rainwater runoff is large and the erosion phenomenon is extremely serious.Therefore,the repair of underground pipe network cannot satisfy the safety of urban rainstorm.As one of the most widely used low-impact measures in sponge city construction,biodetention technology has a significant effect on regulating rainfall and flood,reducing non-point source pollution,etc.,and filler is the key factor of biodetention system function.In addition,artificial floating island technology also has a significant effect on the eutrophication of reservoirs and lakes.Combined with the actual situation of road runoff in chongqing,this study selects the type and proportion of fillers suitable for the biological detention system for the treatment of road runoff pollution in mountain cities,and applies the artificial floating island technology to the treatment of road runoff water quality,providing reference for the pilot and exploration of mountain sponge city construction technology.Firstly,this paper carries out a comparative analysis on the effects of different LID facilities on the treatment of road rainwater runoff pollutants,and proposes to carry out a further study on the seasonings in rainwater regulation ponds and biological detention facilities.Secondly,the types and proportions of the fillers in the bioretention system were studied.Among the ten fillers tested,vermiculite,zeolite and volcanic stone were selected as the preferred fillers.The physical and chemical properties,water holding capacity,permeability and purification of the three fillers mixed with soil by volume ratios of 10%,20%,35%and 50%were studied.The artificial floating island technology was applied to treat road runoff pollutants in the rain pond for the first time,and the plant growth adaptability,packing film,optimal operation parameters and overall purification were studied.The following conclusions were drawn:(1)When vermiculite,zeolite and volcanic stone are used as the preferred fillers to mix with soil at 10%,20%,35%and 50%respectively.The organic matter content was between 2%and 5%,which could be regarded as meeting the requirements of the experimental group.The EC is between 150 and 450,which is consistent with the 1,200 uS/cm under the FAWB rule.After six water trials,the levels of nitrogen in the test groups are not so much,and the concentration of phosphorus is slightly increased,the concentration of organics decreases,and the conductivity is significantly reduced.(2)The water holding porosity and field water holding capacity of vermiculite group are both high.When the proportion is 35%,it shows strong water absorption and water holding capacity.Zeolites and volcanic rocks are less water-holding and water-retaining than vermiculite.When zeolite,zeolite and vermiculite are added into the soil as fillers,the permeability of the system can be significantly improved,reaching the 1 x 10-5m/s required by the guide.The permeability coefficients of the three fillers are volcanic,zeolite and vermiculite from the largest to the smallest,and the ones with better stability are vermiculite,zeolite and volcanic.(3)The purification effect was the best when the vermiculite content was 35%,followed by the zeolite content was 35%and the pyrolith content was 20%.When the content of zeolite and vermiculite is 35%,the TN removal effect is the best.The median removal rate is 78%and 72.5%,respectively.When the proportion of volcanic stone is 20%,the median removal rate is 68%.After adding fillers as fillers,the removal effect of TP was improved and the stability was increased.When the filler is vermiculite and zeolite,the COD treatment effect is the best when the content is 35%,and the median removal rate is 65%and 66%,respectively.At this time,vermiculite is more stable than zeolite.When the filler is volcanic rock,the treatment effect is the best when the content is 20%,and the median removal rate is 64%.When packing for vermiculite,TSS removal effect of overall are good,median removal rate were over 85%,and the whole is relatively stable,content is 35%,the removal effect is best,median removal rate reached 90%,when the packing is zeolite,the median of TSS removal rate were over 80%,content is 35%,the removal effect is best,the median removal rate is 90%,when the packing is volcano,overall on TSS removal effect are not ideal,and only when the content is 20%,the median removal rate reached more than 80%,to 85%.(4)Canna,rehmannia,bambusa and pontoon can grow and develop normally after a month of adaptation.After about 40 days,the packing film was successfully hung to form a biological film of a certain thickness,and the sludge volume was maintained at a certain level,all greater than 0.03g/piece.(5)The operation parameters of DO and HRT were optimized in the rain pond.When the DO content was 3-4mg/L,the removal efficiency was the highest.Selection of HRT for 7 days,5 days and 4 days,dissolved oxygen in 3?4 mg/L,the investigation on pollutants removal effect under three kinds of time,when the HRT for 7 days,the COD and ammonia nitrogen removal efficiency is high,68.38%and 66.02%,respectively,at this time due to the system as a whole in aerobic condition,the TN removal efficiency is not high,removal rate of 32.35%,but due to the low total nitrogen content of storm runoff,water content of total nitrogen in 7?9 mg/L,also meet the level of sewage treatment standard,choose HRT for 7 days.(6)After optimization parameters during operation,enhanced artificial floating island to COD and NH3-N,TN and TP removal efficiency reached 65%,67.85%,30%and 65%respectively,and parameter optimization,the COD and ammonia nitrogen,TN and TP removal efficiency are 55%,35%,25%and 55%respectively,before the optimization parameter COD,ammonia nitrogen and TN removal efficiency increased by 10%,32.85%and 32.85%,respectively,of TN removal rate decreased by 43%,and the effluent COD concentration after optimization are kept under 50 mg/L,ammonia nitrogen concentration is less than 2 mg/L,TN concentration was maintained at 8?9mg/L,all of which met the national first-level standards for urban sewage treatment and discharge.The decrease of TP removal efficiency was mainly caused by the failure to effectively remove the remaining sludge in the anaerobic zone at the bottom and temperature... |
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