Real time control of stormwater biofilters improves the removal of organic chemicals

Abstract

Biofilters are among the most popular nature-based systems for treating stormwater and delivering multiple environmental benefits. However, as a passive system, their performance tends to be inconsistent in removing emerging organic contaminants produced by anthropogenic activities that can be persistent, mobile, and toxic. Thus, in this study, real time control (RTC) of stormwater biofilters is introduced to enhance the removal of a diverse range of organic chemicals. Laboratory columns were employed to investigate the performance of five RTC strategies, i.e., dynamic soil moisture control (RTC-Moisture), infiltration rate control (RTC-IR), pre-drain (RTC-PreDrain), fully unsaturated (RTC-UnSat), and fully saturated (RTC-FulSat). These RTC strategies were tested under varying rainfall sizes, as well as dry and wet conditions. Additionally, the study examined the accumulation of organic chemicals in the media. The results revealed that RTC-Moisture, RTC-IR, and RTC-PreDrain were the top three performing strategies, which achieved a significantly higher removal rate than Non-RTC biofilters for the majority of tested organic chemicals (p-value < 0.05). The best RTC strategy, RTC-Moisture, not only had the highest overall performance (average removal rate of 76.1 %) but was also least affected by various rainfall events. Despite a better chemical removal found in RTC-Moisture and RTC-PreDrain, there was no significant overall increase in the accumulation of organic chemicals within the media (p-value > 0.05) when compared to Non-RTC biofilters. This may indicate that the biodegradation process could be promoted in the well-performing RTC biofilters. This study confirms the possibility of using RTC strategies to enhance organic chemical removal in stormwater biofilters.