In a new study published in Water Research, Yiran Li and colleagues investigated an advanced treatment system for dry wells to address hydrophilic contaminants of emerging concern (CECs) in stormwater. These CECs, commonly found in urban runoff, pose risks to groundwater but are poorly removed by current dry well designs.

The researchers combined UV/H₂O₂ treatment with biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More filters, leveraging three mechanisms: UV photolysis, hydroxyl radical oxidation, and biochar adsorption. Testing on synthetic stormwater showed that this system effectively removed most contaminants. For example, the insecticide imidacloprid, previously a limiting factor, was efficiently degraded, extending the biochar filter’s functional lifespan. The study predicted that in Los Angeles, a 10 wt% biochar filter would last approximately four years under realistic conditions, even without UV pre-treatment.

The addition of UV/H₂O₂ further reduced contaminant loads on the biochar, ensuring compliance with regulatory limits. However, compounds like dicamba—resistant to both photolysis and adsorption—highlight the need for monitoring other anionic pollutants in runoff.

The findings demonstrate the feasibility of retrofitting dry wells with this dual approach, offering an economical and sustainable solution for stormwater management. The system aligns with routine maintenance cycles, making it practical for urban deployment to safeguard groundwater while enhancing stormwater capture efforts.

This research paves the way for improving dry well performance and advancing sustainable water management in drought-prone regions.

SOURCE: Li, et al (2025) Combined UV/H₂O₂ and Biochar Processes for Enhanced Removal of Contaminants of Emerging Concern in Dry Wells. Water Research. https://doi.org/10.1016/j.watres.2025.123159