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The Next Chapter On Nutrients: You can trade that?

This article authored by Jennifer Ruddy, P.E., appeared in the May 2017 issue of the Iowa League of Cities publication, Cityscape.

 What are nutrients, and why are nutrients important to my city?

Nutrients are essential to sustain all life forms and are the focus of our discussion today. Of interest to cities are two nutrients contained in overland runoff and municipal and industrial wastewater effluents: total nitrogen (TN) and total phosphorus (TP). These nutrients are essential for a healthy aquatic ecosystem; however, when their levels in water bodies are too high, damage to the ecosystem can occur.
The Iowa Nutrient Reduction Strategy (INRS) was released in November 2012. It includes a joint strategy for non-point sources – agriculture and urban stormwater sources, and point sources – commonly industrial and municipal wastewater treatment facilities (WWTF) to reduce the TN and TP loading to the Mississippi River by 45%.  For major municipal WWTFs, the INRS goal is to meet future limits based on 10 mg/L TN and 1 mg/L TP.

What is nutrient trading and why should it be considered?

Nutrient trading is included in the final draft and annual updates of the INRS as a potential method of meeting nutrient removal goals at the WWTF (point source). Nutrient trading is generally much more cost-effective for removing nutrients at non-point sources than from point sources. Nutrient trading sets up a system whereby WWTF improvements may, in some cases, be avoided by implementing watershed-based (non-point source) improvements that provide the same or better reductions in nutrients, but at a much lower cost.

A nutrient trading system may provide a city’s WWTF (point source) an opportunity to purchase credits generated by water quality improvement projects that were implemented for other benefits like flood mitigation, water source protection, or economic development.

Does Iowa have a nutrient trading program, and how does it work?

The League of Cities has started building the framework for a Nutrient Reduction Exchange (NRE) program, a statewide registry for nutrient reductions. The NRE would be scoped with similar verification and requirements that would be needed for future trading. This work is made possible by a Conservation and Innovation Grant from the United States Department of Agriculture (USDA) and Natural Resources Conservation Service (NRCS).

The NRE allows cities or industries to register nutrient reductions generated by watershed improvements projects; cities can then have those reserved nutrient reductions available to meet future, more stringent nutrient limits at point sources.

For example, if a city is currently investing in a flood mitigation project, they could track nutrient removal benefits from the flood improvements. Those benefits could then be used later to offset more stringent regulations on nutrients that the city faces at their WWTF. The League is working with the Iowa Department of Natural Resources (IDNR) and a stakeholder group to identify incentives for early adoption and investment.

Are there opportunities to participate in the program?

Water quality improvements from both rural and urban watershed projects can qualify for the NRE. The projects and, as a result, nutrient reductions could be driven by flood mitigation, stormwater management, environmental or sustainability benefits, source water protection, economic development, and habitat or species development and protection. Some Iowa cities are taking part in the sponsored project program, and the nutrients reduced by the sponsored projects can be registered with the NRE.

As part of the USDA grant, there are currently NRE pilot projects underway in Storm Lake and Dubuque where urban and rural watershed projects are being tracked to determine which water quality benefits, including nutrient reduction, are realized when the projects are complete. Projects are expected to improve water quality by reducing sediment, nitrogen, and phosphorus entering Iowa waterways.

How are reductions measured?

The NRE will use a science-based approach for measuring the nutrient reduction capabilities of an installed water quality improvement project. The Iowa League of Cities NRE Project Team has discussed with IDNR using predictive models to determine the nutrient removal capability of these projects. The models are developed based on nutrient data collected from watershed improvements. Depending on the model chosen by a city to predict nutrient removal capacity of a watershed improvement project, IDNR may require additional data collection to determine the nutrient removal treatment efficiency.

Nutrient reductions calculated by these models could then be registered with the NRE. The Project Team and IDNR are developing the nutrient trading ratio that will be available to participants. A common ratio used by other states for compliance-based trades requires two nutrient credits from watershed improvements to offset one nutrient credit at a point discharge source. The Project Team and IDNR are trying to determine opportunities for better exchange ratios for early participants in the NRE program.

What is the importance of the NRE to cities?

The NRE provides an opportunity for cities to voluntarily register the nutrient reduction benefits from their water quality improvements projects. Depending on the final structure of the NRE and additional tracked benefits offered to cities for water quality improvements projects, the NRE may provide another option for cities to meet nutrient limits while tackling other watershed issues.

Ms. Ruddy is a project manager at FOX Engineering in Ames. She focuses on the design of water and wastewater treatment plants, evaluation of treatment plant hydraulics, modeling water distribution systems, and construction administration. She has bachelor and master’s degrees in engineering from Iowa State University.

FOX Engineering is an environmental engineering firm based in Ames, Iowa. We specialize in water and wastewater solutions for our diverse municipal and industrial clients. Our work varies in size and scope and can be found throughout the Midwest and beyond.