Study On Pollution Control Efficiency And Mechanism Of Application Of Construction Waste In Stormwater Infiltration Facilities

With the accelerating urbanization process,the increase of impervious areas has brought great pressure to the urban drainage system.As the main product of urban demolition,construction waste not only occupy a large amount of land resources,but also bring greater pollution risks to the urban ecological environment.At present,some studies have found that construction waste have certain removal effects on certain pollutants.It shows that construction waste have certain application potential in the field of water treatment.The percolation facilities in sponge cities are a kind of rainwater treatment and collection methods commonly used in some developed countries.The percolation facilities are generally composed of soil,gravel and sand.The construction waste are used in the percolation facilities.Certain feasibility.The main mechanism of construction waste to remove pollutants and the possibility of its application are still in the process of exploration.In this study,the dynamic column experiment was used to simulate the removal effect and mechanism of heavy bricks and conventional pollutants in building sponges used in sponge infiltration facilities.The purpose of this study was to investigate the hydraulic conditions of construction waste used in sponge percolation facilities and for sponges.The feasibility of the percolation facility provides direction for the recycling of construction waste and reduces the construction cost of the sponge infiltration facility.Through the study on the removal efficiency of pollutants from construction waste,the main conclusions are as follows:?1?In the experiment of removing Cu²⁺from rainwater in lime sand bricks,it is found that the bed height,residence time and initial concentration have certain influence on the removal of Cu²⁺.The initial concentration and residence time are shown by the Box-Behnken design in the response surface.The removal of Cu²⁺by lime sand bricks has a significant effect,and the bed height has little effect on the removal of Cu²⁺.Continuous extraction showed that the different forms of copper in lime sand bricks were:organic bound state>iron manganese oxidation state>carbonate bound state>residual state>exchangeable state.The iron-manganese oxidation state and residual state of bricks are more,indicating that the lime sand bricks after copper adsorption can reduce ecotoxicity and bioavailability.?2?The results of dynamic column experiments on the removal of common pollutants from rain bricks in construction waste show that the removal effects of COD,TN and heavy metals in construction waste?CW1?and construction waste?CW2?are similar.The effluent pH of the two construction waste is higher than the influent pH,and the pH value of the effluent increases with the increase of the residence time,but they all meet the surface water discharge quality standards;the removal of NH₄⁺-N by the two construction waste bricks As the residence time increases,the CW1 is more stable than the CW2 during the operation of the system;in the TP removal process,at the lower residence time,the CW1 is more than the CW2.The removal rate of CW2 is high and more stable.The removal effects of different construction waste on different heavy metals(Cu²⁺,Zn²⁺and Mn²⁺)were similar,and the removal effect was better with the increase of residence time,and both Cu²⁺and Zn²⁺were better removed.Microbial 16S sequencing results showed that there were a large number of denitrifying and dephosphorizing bacteria on the surface of construction waste bricks.Different construction garbage bricks have certain similarities under different residence time conditions,and there are certain differences.?3?In the sponge percolation facilities used for artificial simulation of construction waste,it is found that there are pollutants released in different systems.In the results of construction construction waste,the amount of COD,NH₄⁺-N,Zn²⁺and Pb²⁺is less than that of the structure without added construction waste,while the release of TN and Cr⁶⁺is larger.Under the different sampling time conditions of the same experiment,it is found that different systems have better removal effects on NH₄⁺-N and TP.TN is still in the process of release.Different systems have better removal effects on Cu²⁺,Zn²⁺,Cd²⁺and Pb²⁺.A large amount of Mn²⁺is released in the system of adding sand.During long-term operation,the pH of the effluent meets the relevant quality standards.The removal effect of construction waste on TN,COD,TP,Cu²⁺,Zn²⁺,Cd²⁺,Mn²⁺and Pb²⁺is good.With the extension of time,the removal effect of construction waste on TN is getting better,but the construction waste are better.The removal effect of Cr⁶⁺was slightly worse.The microbial content and type of different layers in the“soil+sand+gravel”and“soil+fine brick+coarse brick”structure were detected by microbial 16S sequencing,and it was found that the system containing construction waste contained more genus of nitrogen and phosphorus removal,waste construction blocks comprising the system described in nitrogen and phosphorus removal effect of the action of microorganisms is more obvious.