Laboratory assessment of media clogging in bioretention systems: Effects of sawdust addition, plant species and dry-wet alternation

Bioretention system has received increasing attention as a more natural approach to stormwater management, while clogging is recognized as the main limiting factor in its long-term operation. In this study, a laboratory scale bioretention systems were constructed to investigate the influence of different factors on the media clogging. The addition of sawdust in filter media (sand and sandy loam soil mixture) had no obvious effect on suspended solids (SS) accumulation and matrix porosity in different depth of filter, but effectively increased the hydraulic conductivity of bioretention systems. Similarly, there was also no significant difference in spatial or temporal variations in SS accumulation between three systems with different plants (p > 0.05). Nevertheless, plant species had significant influence on the hydraulic conductivity, with Acorus calamus L. demonstrating to be appropriate to mitigating the clogging (p < 0.05). Dry-wet alternation helped to improve the hydraulic performance. The results showed that the upper layer (0-20 cm) was more prone to clogging while dry period was conductive to alleviating media clogging no matter in summer or winter rainfall mode. This study will contribute to a greater understanding of the hydraulic performance and provide guidance for alleviating media clogging in bioretention systems.