Nutrient and Sediment Reductions from Algal Flow-Way Technologies: Recommendations to the Chesapeake Bay Program's Water Quality Goal Implementation Team from the Algal Flow-Way Technologies BMP Expert Panel

Authors: BOTT, CHARLES - Old Dominion University; BRUSH, MARK - Virginia Institute Of Marine Science; CANUEL, ELIZABETH - Virginia Institute Of Marine Science; JOHNSTON, MATT - University Of Maryland; KANGAS, PAT - University Of Maryland; LANE, SARAH - University Of Maryland; MAY, PETER - Biohabitats, Inc; Mulbry, Walter; MULHOLLAND, MARGARET - Old Dominion University; SAMPLE, DAVE - Virginia Tech

Submitted to: Technical Report
Publication Type: Other
Publication Acceptance Date: 9/1/2015
Publication Date: N/A
Citation: N/A

Interpretive Summary: A cross-sector panel of experts was formed to explore the potential benefits of using algal raceways to remove dissolved nutrients from streams and drainage ditches. The panel reviewed existing literature and data related to the nutrient reduction benefits of this technology, and concluded that these practices remove nutrients and sediment that could be modeled as reductions to estimated polluted runoff in the Chesapeake Bay Program Partnership’s Watershed Model. In addition, the panel made recommendations on how the practice should be quantified, reported, tracked and modeled by the Chesapeake Bay Program. These recommendations will be forwarded to appropriate workgroups within the Bay Program for review and approval prior to final approval and subsequent incorporation into the Chesapeake Bay Program Partnership’s modeling tools. These results, and the process that they are part of, are important steps in the approval and adoption of this technology as a best management practice for improving water quality in sensitive watersheds.

Technical Abstract: The Chesapeake Stormwater Network hosted a workshop on July, 2012 to discuss the potential nutrient reductions from emerging stormwater technologies including algal flow-way technologies (AFTs). Workshop participants recommended the Chesapeake Bay Program’s Water Quality Goal Implementation Team(WQGIT) form a cross-sector panel of experts to further explore the potential nutrient reduction benefits of algal flow-ways. The panel’s review followed the process described in the protocol for the Development, Review, and Approval of Loading and Effectiveness Estimates for Nutrient and Sediment Controls in the Chesapeake Bay Watershed Model. This protocol requires the panel to review existing literature and data related to the nutrient reduction benefits of the BMP, and make initial recommendations on if and how the BMP should be quantified, reported, tracked and modeled by the Bay Program. These initial recommendations are forwarded to the appropriate source sector workgroups (Agriculture Workgroup and Urban Stormwater Workgroup) and the WTWG for review and approval. After this initial review phase, the panel’s recommendations are sent forward to the WQGIT for final approval and subsequent incorporation into the Chesapeake Bay Program Partnership’s modeling tools. After reviewing the available science related to algal flow-way technologies, the expert panel concluded that these practices remove nutrients and sediment that could be modeled as reductions to estimated polluted runoff in the Chesapeake Bay Program Partnership’s Watershed Model. Only operators that transport the nutrients and sediment offsite for end use or disposal, or apply the nutrients according to a nutrient management plan are eligible for this credit. The panel agreed that jurisdictions could qualify for nutrient reductions in one of two ways. For planning scenarios and for those operations or jurisdictions that do not have access to regularly sampled algal production weights and nutrient concentration analyses of algae produced, a jurisdiction may claim a reduction of 545 pounds of total nitrogen (TN) and 45 pounds of total phosphorus (TP) per acre of AFT surface area in operation each year. These “default” reductions are based upon conservative algal production and nutrient concentration estimates of systems in operation around the Chesapeake Bay Watershed. According to the studies provided in Table 2, the Panel conservatively estimated that one acre of AFT surface area would produce approximately 25,000 pounds of algae (dry weight basis) in a single year. The panel also estimated that algal nitrogen and phosphorus content would be 2.2% and 0.18%, respectively. Alternatively, jurisdictions have the option to submit results from nutrient concentration analyses of biomass produced by an AFT project along with the dry algal weight of biomass produced. This would result in a more accurate accounting of nutrients removed by these systems. These procedures are considered sufficiently general enough to apply to multiple variants of the AFTs.