Experimental And Applied Research On Improving Configuration Of Typical Soil Seepage Water And Water Quality Treatment Performance In South China

With the acceleration of urbanization,urban drainage pressure is increasing,and runoff pollution is serious.Through the 13th Five-Year Plan,the government put forward the requirements for the construction of sponge cities,trying to achieve the control of total runoff and pollution through the wide application of low-impact development measures such as biological detention pools and concave green space,but these measures all depend on urban green space.The typical red soil in South China has high acidity,heavy stickiness and low soil infiltration performance,which greatly affects the design and construction of green space in South China.How to rationally and scientifically improve soil infiltration and water treatment performance is very important.In this paper,the effects of organic and inorganic materials with different weight ratios（10%,20%,40%and 60%）on soil infiltration and water treatment performance were studied by plastics column installation.The materials include landing,zeolite,gravel,leaves and grass roots.Based on the experimental results of this stage and the theoretical basis of biological detention tank structure,suitable filling materials were selected to study the effect of self-made filter column device on reducing runoff water and pollution under complex structure.Finally,combined with the hydraulic module of storm flood management model SWMM,the flow process of actual test filter column was simulated.The main research work is as follows:（1）Study on the improvement of soil infiltration and water treatment performance under simple structureResearch on seepage storage.The infiltration time span,initial runoff yield time and peak infiltration rate of improved soils were shortened with the increase of material content.In the single material experiment,the inorganic material 5⁸mm zeolite obtained the maximum seepage rate,and showed the fastest or near the fastest runoff-producing material;while the improvement effect of organic material leaves on soil infiltration was always better than that of grass roots,and leaf runoff was faster than that of grass roots,and 1%of grass roots had the slowest runoff.In the multi-material experiment,the combination of upper organic material leaves and lower inorganic material zeolite has a greater water seepage advantage.Research on water quality treatment.The outflow SS,NH₃-N concentration and pH value increased with the increase of the weight ratio and particle size distribution of the improved soil mixtures.In the single material test,the outflow values of SS,NH₃-N and COD from 0.5²mm seasand of inorganic materials were lower than those from other materials,and the outflow values of pH from 5⁸mm gravel were the lowest.The outflow values of SS,NH₃-N,COD and pH from grass roots of organic materials were always lower than those from leaves.In the multi-material test,the concentration of SS and NH₃-N in the mixed effluent of upper and lower layers of inorganic and organic materials is less than that of any single material,while the pH value is larger than that of any single material.When two organic materials are added to the upper layer,the law of effluent concentration becomes more complex.（2）Reduction effect of self-made filter column device on total runoff and pollution under complex structureResearch on total runoff.The rational use of filling materials can significantly improve the seepage storage effect of red soil.With the increase of rainfall recurrence period,the peak infiltration rate of each filter column increases gradually,while the time of seepage generation and peak infiltration rate occurs earlier,and the reduction rate of total runoff by each filter column decreases accordingly.Zeolite>landing ash>gravel achieved the best seepage rate at the same recurrence period,and the total reduction rate of zeolite runoff was always the largest,reaching nearly 70%at the recurrence period of 1a.Research on runoff pollution.Gravel>zeolite>landing ash>pure soil achieved the best SS removal effect,and the maximum SS reduction rate reached 41.94%.Gravel>zeolite>ground ash>pure soil achieved the best removal effect of NH₃-N,and the maximum reduction rate of NH₃-N reached 83.4%.The COD of effluent after each filter column material is larger than the original data of influent.The COD concentration of pure soil filter column is the highest,which is 2.64 mg/L,while that of zeolite filter column is the lowest,which is only 1.272 mg/L.The effluent pH of pure soil filter column is less than the original data of water inflow;the pH of filter column filled with various materials increases,and the outflow value of landing ash filter column is the largest,the effluent is weak alkaline.（3）The filter column filled with ground ash is selected to simulate the hydrology of SWMM LID module.The hydrological simulation of LID module of SWMM model is carried out by using filter column filled with ground ash.When the recurrence period is 1a and 5a,the fitting degree between the test value of self-made filter column outflow and SWMM simulation value is slightly different,but the overall coincidence degree of infiltration curve is relatively high.This is due to several reasonable calibrations of model parameters based on the experimental results in the simulation process.