Research On The Clogging Of Foam Plastic Filter Layer Infiltrated With Storm Water

Filter layer is an important part of sponge city infiltration system,but the clogging phenomenon is the key to its performance attenuation.The traditional filter layer designed for storm-water infiltration system is made of gravel or geotextile,and it lacks effective maintenance and performance recovery measures for clogging because buried underground.Improving the filter layer from material and structure types to make it easy to maintain and update is crucial to guarantee the long-term performance of infiltration facilities.Foam plastics,with excellent pore structure characteristics,can be used as filter layer to ensure certain permeability,but also provide accommodation space for clogging particles;Taken a detachable structure scheme,the filter layer can be cleaned and replaced after clogging which makes maintenance and management practical.Based on the characteristics of measured storm-water suspended matter and selected several foam plastic specifications,through infiltration simulation test of suspended solids solution,the article studied the phenomenon of suspended particles staying at the inlet of filter layer,clogging in filter layer and penetrating filter layer and analyzed the law of physical and biological clogging,which underlay the material specifications selecting of filter layer.And it also explained the reliability of detachable structure scheme to some extent.For the samples after the infiltration simulation test,micron-level CT scanning was used to investigate the distribution of fouling inside the foam plastic filter layer at a meso level.The main contents and conclusions of this article are as follows:(1)Through the storm-water sampling survey in Jiuwanfang Experimental Base,Changjiang River Scientific Research Institute,the typical characteristics of storm-water suspended particles in the study area were analyzed,the particle sizes were less than 1.0mm,and the concentration was 140 ? 2500 mg /L.(2)The particle sizes less than 1.0mm were divided into 5 particle groups to prepare suspension solution separately and 6 foam plastic specifications were selected to carry out infiltration simulation tests.The results showed that coarse particles larger than 0.25 mm was easier to deposit at the inlet of the filter layer;for fine particles of 0.1?0.25 mm and <0.1mm,the corresponding filter specifications which had the best filtration were 80 ppi and 100 ppi,respectively.(3)On the basis of the above mentioned material selection tests,5 different concentrations of suspension solutions using combined graded suspension particles were prepared and two filter layer specifications of 80 ppi and 100 ppi were used to carry out infiltration simulation tests.The results showed that the greater the concentration of suspended solid particles,the faster the permeability coefficient decreases,and it meant the clogging speed was faster under the same filter layer pore size.(4)Against the effect of biological activity on the clogging of foam filter layer during rainfall interval was considered and the biological clogging simulation test under intermittent seepage was conducted.The results showed that microfilm growth caused a certain decrease of the filter permeability coefficient;but it was inferior to physical clogging caused by suspended particles.