Performance evaluation for a stormwater treatment train incorporating sedimentation and geomedia-augmented biofiltration

Beach closures are detrimental Minnesota’s waterfront recreation opportunities, which are key component to Minnesota’s cultural identity. For example, Agate Bay and Burlington Bay in Two Harbors have faced periodic closures associated with Escherichia coli (E. coli), while excessive nutrient loads have degraded water quality and affected recreational water access across the state. Urban runoff may also contain other harmful contaminants, including metals and organic contaminants.

This project will evaluate the efficacy of a full-scale geomedia-augmented best management practices (BMPs) for achieving water quality improvements at the catchment scale, in response to Research Priority Area 2. The Lake County Soil and Water Conservation District (LCSWDC)
has received funding from the US Environmental Protection Agency (US EPA) Great Lakes Restoration Initiative (GLRI) to install a stormwater treatment train incorporating two-stage sedimentation and biochar-augmented biofiltration to manage degrading water quality in Agate Bay, Two Harbors. The Natural Resources Research Institute (NRRI) will work closely with LCSWDC to evaluate the hydraulic and contaminant load reduction performance of the system during the first two operational seasons. We will evaluate treatment efficacy for a suite chemical and biological contaminants, including sediment, nutrients, metals, E. coli,
and organic contaminants. We will also characterize the biofilm developed on the aged filter media to determine if microbial communities established on aged filter media indicate desirable biological functionality (i.e., functional diversity, presence of nutrient-cycling bacteria). Our findings will be summarized in a final report with best practice recommendations for future implementation of geomedia-augmented biofilters to address impaired waters.

Projected outcomes

  • Improved near-shore water quality at Agate Bay beach in Two Harbors to enable safe public recreation and reduced frequency of beach closures
  • Increased accessibility for practitioners to best practice recommendations regarding the design of treatment trains incorporating sedimentation and geomedia-augmented biofiltration
  • Broader implementation of an emerging BMP, with potential for future incorporation of Minnesota-sourced biochar and iron-containing materials
  • Establishment of a new client bases for future application of Minnesota-sourced biochar and iron-containing materials in stormwater treatment systems across Minnesota
  • Broader implications that are vital to the health and well-being of urban residents, including mitigation of water pollution and improved accessibility to waterfront recreation