Biofiltration is a common stormwater treatment practice throughout the state of Minnesota, particularly in urban areas. However, professionals continue to face design challenges pertaining to media mixes, particularly those containing compost which have been shown to export phosphate which can cause algal blooms in lakes. This study consists of 30 outdoor biofiltration mesocosms comprising nine different media mixes compared to clean washed sand (three replicates of each mixture). Media components were mixed with clean washed sand to produce mixed media, including food residue compost (10% or 20%), leaf compost (10% or 20%), sphagnum or reed sedge peat (20%), 15% biochar mixed with 20% leaf compost, 5% spent lime mixed with 20% leaf compost, or 5% iron mixed with 20% leaf compost. Over two years, a series of 22 simulated runoff events were conducted approximately weekly and the effluent and influent phosphorus measurements were compared. This presentation will share performance results on filtration rate, effluent phosphate concentration, and vegetation growth. We will also discuss upcoming additional metrics including application of road salt on our media and an indoor vegetation germination study to examine low organic content ( < 10% compost) media mixes. With the information from this study, stormwater practitioners will be able to design better biofiltration practices that capture phosphorus and support healthy vegetation while also maintaining adequate filtration rates.
Co-authors include: Andy Erickson, St. Anthony Falls Laboratory, University of Minnesota, 2 Third Ave SE, Minneapolis, MN 55414, 612-239-2046, eric0706@umn.edu Jessica Kozarek, St. Anthony Falls Laboratory, University of Minnesota, 2 Third Ave SE, Minneapolis, MN 55414, 612-624-4679, jkozarek@umn.edu Katie Kramarczuk, St. Anthony Falls Laboratory, Water Resources Science, University of Minnesota, krama024@umn.edu Laura Lewis, St. Anthony Falls Laboratory, Civil, Environmental, and Geo-Engineering, University of Minnesota, lewi1197@umn.edu
Learning Objectives:
Articulate the difference between biofiltration practices and other similar practices such as rain gardens, bioinfiltration practices, and bioretention practices.
Describe various media components that could be used in biofiltration practices, such as sand, compost, peat, and enhancing amendments like iron, spent lime, and biochar.
Compare and contrast the benefits and consequences of using different media components in a biofiltration media mix design.
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