UC San Diego

Biofiltration systems use a variety of biological, chemical, and physical processes to capture and improve the water quality of stormwater runoff. Biofilters are frequently specified for design in construction projects in southern California, but are rarely monitored for long-term success. Typically, the engineering design criteria are focused on the hydrologic aspects, soil type, and vegetation, but rarely consider the benefits of ecological services or the presence of fauna. By improving our understanding of biofilters, we can introduce a scientific component to an engineered design that does not typically consider the benefits of a man-made ecosystem. Four biofilters constructed in 2010 at the Scripps Institution of Oceanography were selected as a model to examine existing biofilter function based on biofilter pollutant removal capabilities and ecosystem structure. Historic and current analysis of the biofilters show that concentrations of total copper, total zinc, and total suspended solids were reduced by the biofilter, though the percent pollutant removed has decreased over time. Nutrient and bacteria removal is more complicated, with input rather than removal during some periods; improvements could be made to optimize this. Recommendations to improve the sustainability and longevity of biofilters based on the data and literature include a) the incorporation of a saturated zone, b) the use of rain barrels, c) outreach and education, and d) further local experimentation on the relationship between biofilter flora and fauna.