Enhancing Denitrification in Constructed Wetlands with Pyrrhotite and Oyster Shells
Mentor Information
Sarina Ergas (Department of Civil & Environmental Engineering)
Description
There are many sources of nitrate pollution that contaminate local waterways, thereby posing risks to human health and surrounding ecosystems. Recent research has showed the potential of constructed wetlands containing pyrrhotite mineral as a low-cost and sustainable approach for treating nitrate contaminated wastewater through a natural biological process called denitrification. The use of pyrrhotite, however, has led to secondhand sulfate production, which is known to inhibit plant growth and nitrate uptake. This batch reactor study examined whether a combination of pyrrhotite and an inorganic carbon source (oyster shells [OS]) could enhance the denitrification process while minimizing sulfate generation. The study was carried out in sixteen batch reactors, each filled with synthetic wastewater and a unique variation of mineral, OS, and microbial inoculum. Three reactors contained only pyrrhotite added, three with only OS, and three with pyrrhotite and OS combined. Additionally, three reactors were endogenous decay controls, three were abiotic controls, and one contained elemental sulfur. Over the course of ten weeks, the reactors were monitored weekly for changes in sulfate, nitrite, nitrate, ammonium, and phosphate concentrations. While denitrification was accelerated in the reactors containing pyrrhotite, there was little difference between the pyrrhotite only and the pyrrhotite and OS reactors in terms of sulfate generation. The outcome of this study guides further research in the continued refinement and optimization of the constructed wetlands for water quality treatment. Ultimately, this work will enable the introduction of constructed wetlands into small communities for use in lowering nitrate pollution in nearby ecosystems.
Enhancing Denitrification in Constructed Wetlands with Pyrrhotite and Oyster Shells
There are many sources of nitrate pollution that contaminate local waterways, thereby posing risks to human health and surrounding ecosystems. Recent research has showed the potential of constructed wetlands containing pyrrhotite mineral as a low-cost and sustainable approach for treating nitrate contaminated wastewater through a natural biological process called denitrification. The use of pyrrhotite, however, has led to secondhand sulfate production, which is known to inhibit plant growth and nitrate uptake. This batch reactor study examined whether a combination of pyrrhotite and an inorganic carbon source (oyster shells [OS]) could enhance the denitrification process while minimizing sulfate generation. The study was carried out in sixteen batch reactors, each filled with synthetic wastewater and a unique variation of mineral, OS, and microbial inoculum. Three reactors contained only pyrrhotite added, three with only OS, and three with pyrrhotite and OS combined. Additionally, three reactors were endogenous decay controls, three were abiotic controls, and one contained elemental sulfur. Over the course of ten weeks, the reactors were monitored weekly for changes in sulfate, nitrite, nitrate, ammonium, and phosphate concentrations. While denitrification was accelerated in the reactors containing pyrrhotite, there was little difference between the pyrrhotite only and the pyrrhotite and OS reactors in terms of sulfate generation. The outcome of this study guides further research in the continued refinement and optimization of the constructed wetlands for water quality treatment. Ultimately, this work will enable the introduction of constructed wetlands into small communities for use in lowering nitrate pollution in nearby ecosystems.
