Performance Evaluation of Alternative Biofilter Media Amendments

This work is part of a multi-disciplinary project investigating the use of alternative media for biofiltration systems in Minnesota. Over the last thirty years, the Minnesota Department of Transportation (MnDOT) has implemented biofilters along roadways as a stormwater control measure. These systems must be able to infiltrate and treat the first inch of rainfall onsite to meet state and national regulations. The performance of a biofilter is largely based on its media's ability to infiltrate water, sustain vegetation, and capture pollutants. To date, MnDOT has relied on sand and compost mixtures for biofilter media amendments. An early phase of this work identified peat as having similar performance characteristics as compost, making it an ideal alternative. A laboratory testing program was also developed during the early phase of work to determine media properties that could be used to predict biofilter performance. Current work focused on characterizing existing biofilters using in situ testing and comparing results to laboratory testing. The comparison of the two methods has enabled an analysis of the predictive capabilities of the laboratory regime. This work also included the instrumentation and monitoring of field sites including a newly constructed peat amended biofilter. Findings from this work have validated the use of peat as a biofilter amendment and shown the developed laboratory testing regime to be a good indicator of field performance. The characterization regime developed through this project and instrumentation methods will be used in the future to identify other beneficial alternative biofilter medias.