Brenda Read

Project Title: "Stimulating nitrogen removal in headwater streams using sulfur-based denitrification "

External Partnership: The Nature Conservancy-Indiana

The extensive use of fertilizers in agriculture has led to widespread eutrophication of water bodies.  Eutrophication occurs when excess nutrients, such as a nitrogen or phosphorus, are deposited into receiving bodies of water. An extreme example of eutrophication is the “dead zone” in the Gulf of Mexico, which is a consequence of wide-spread fertilizer use in the Midwest. The negative ecological consequences of eutrophication include damaged aquatic life and reduced drinking water quality. Since nitrate-laden agricultural discharges are a nonpoint source of pollution, it is not feasible to treat them with conventional, centralized technologies. One way of removing nitrates from the environment is through biological denitrification. Denitrifying microorganisms are naturally present in stream sediments, but they often lack an electron donor, needed to convert nitrate to innocuous nitrogen gas.  A new approach is to stimulate denitrification in headwater streams that drain agricultural fields with elemental sulfur as the electron donor. Sulfur-based denitrification technologies have proven effective in ground water and wastewater treatment systems, but have yet to be applied to streams. Elemental sulfur is nontoxic, insoluble and inexpensive.  It is a commonly used as a soil amendment for adjusting pH, and can be purchased at agricultural supply stores.

In her research, Brenda and her partners tested the efficacy of elemental sulfur to enhance in-stream denitrification.  In previous research elemental sulfur particles were added to a lab-scale simulated stream. Nitrate removal efficiencies exceeding 90% were found.  A better configuration for removing nitrates from the environment is two-stage ditches. Two-stage ditches restored streams to a more natural flow regime because they provided storage during high flow events, giving more contact time for microbial denitrification.  In order to study sulfur-based denitrification in a two-stage ditch, under more realistic conditions, Brenda modified mesocosm to mimic two-stage ditch conditions, and using actual two-stage ditch sediments and stream water in our mesocosm. During this research Brenda measured nitrate removal rates and sulfate production. She also studied practical approaches to applying and retaining the sulfur in a ditch.  This research provided performance data and realistic implementation strategies for sulfur-based denitrification. Partner research continues with the Tank Research Group in Biological Sciences at Notre Dame who are currently studying two-stage ditches. Brenda also partnered with Dr. John Shuey of The Nature Conservancy (TNC).  All of this research has helped to design a low-technology sulfur-based system capable of removing nitrates near their source.  This system may be used as part of a TNC nitrate management program or as an agricultural best management policy.

Distinctive Outcomes: Brenda is doing research with TNC to develop techniques for the removal of excess nitrogen from agricultural run-off.