Biofiltration has become common in Minnesota’s urban landscape because it is one of the most robust stormwater treatment practices available to designers. Stormwater professionals and practitioners, however, are uncertain when selecting media components because some recommended biofiltration media mixes have been shown to export phosphate, potentially contributing to water quality impairments.
In Phase I of this research, we measured phosphate release, filtration rate and plant growth in common biofiltration media mixes with various local materials. Questions remain as to the long-term performance of these mixes, in particular, in the presence of other pollutants such as road salt. In addition, due to phosphate release from high compost mixes, there is interest in media mixes with low organic content. The ability of these low-organic content mixes to support plant growth is unknown. To answer these questions, the objectives of Phase II are to:
- Evaluate the multi-year performance of locally sourced media mixes by extending the experiments in Phase I three more years.
- Investigate the interactions between phosphate release and road salt in both aged and new mesocosms.
- Test plant growth in low-organic content mixes.
- Develop guidance and training to disseminate knowledge gained through this research.
These results will be incorporated into existing or new professional training, continuing education, and certification for stormwater professionals and practitioners. This study will fill existing knowledge gaps for designing biofiltration media mixes in Minnesota thus allowing practitioners to design biofiltration practices with the best available knowledge of media components in Minnesota.