Clogging mechanism of bioretention cell with fine-grained soil medium

Abstract

In order to explore the clogging mechanism of bioretention cells containing fine-grained soil medium, four groups of bioretention cell were constructed. The clogging process was studied in bioretention cells, under simulated runoff conditions with varying suspended solid (SS) concentrations, determining the microbial clogging process at different degrees of SS clogging. Results showed that SS caused clogging in the upper and shallow layers of the filler material. When the concentration of SS was low, clogging of the bioretention column occurred mainly in the shallow layer of the filler, while at SS concentrations higher than 300 mg/L, clogging mainly occurred in the upper layer of the filler. Microbial clogging caused by continuous rainfall occurred in all filler layers. Furthermore, bioretention cells suffering from severe clogging by SS were more likely to also suffer from microbial clogging. Microbial clogging can be effectively mitigated by ensuring that the bioretention cell has adequate drying periods, although this approach has a limited effect on the restoration of bioretention cells with a submerged zone. In bioretention cells exhibiting serious physical clogging, the proportion of microbial clogging can reach 44 %. In the practical application of bioretention cells, replacement of the upper filler layer is the most direct method to effectively relieve clogging, while setting a drying period is effective for alleviating microbial clogging. The experimental results revealed the clogging mechanism in the bioretention cell from two aspects, establishing effective approaches for the reduction of filler clogging and providing a theoretical basis for the practical operation of bioretention cells.