Determining organic copper speciation in stormwater and wastewater to improve treatment and regulation

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The pollution of surface water systems by heavy metals is a global environmental challenge. Heavy metals are released to surface water systems through anthropogenic activities including the generation and discharge of wastewater and stormwater. The interactions of heavy metals with dissolved organic matter (DOM) are key drivers of their fate, transport, and toxicity in aquatic systems. Copper (Cu) is of particular importance in this regard due to its strong interactions with DOM and toxicity to a broad range of aquatic organisms including threatened and endangered salmonid species. The current understanding of Cu speciation in wastewater and stormwater is largely based on analytical methods and assays that provide information on species bulk concentration and complexation to organic ligands. Although these studies have revealed that over 99% of Cu in wastewater and stormwater is bound to organic ligands, a detailed characterization of the chemical identity of these ligands and their interactions with Cu ions in anthropogenic waters has remained elusive. The overarching goals of this project are to 1) characterize and identify the organic ligands that interact with Cu in stormwater and wastewater and 2) evaluate and quantify the impact of these anthropogenic metal binding ligands on Cu chemical speciation and efficacy of removal using sorption-based water treatment processes. The successful completion of this research will benefit society through the generation of new fundamental knowledge and validated models to advance the design and implementation of more efficient and cost-effective sorbents and treatment processes to remove heavy metals such as Cu from wastewater and stormwater prior to their discharge into receiving surface water systems. Additional benefits to society will be achieved through educational and outreach activities including the training and mentoring of one graduate student at Oregon State University. The complexation of heavy metals with dissolved organic matter (DOM) plays a key role in controlling their uptake, bioavailability, and toxicity once they enter aquatic systems from various sources. Compositionally, there is evidence that the DOM in wastewater and stormwater differs from natural DOM isolated from surface water systems in both character and metal binding properties. However, a detailed knowledge of the chemical composition, molecular features, and metal binding properties of the organic matter present in stormwater and wastewater has remained elusive. The goal of this research is to characterize and identify metal-binding ligands present in stormwater and wastewater and evaluate the impact of metal-organic binding on the chemical speciation of Cu and the efficacy of Cu removal from these anthropogenic waste streams using activated carbon and biochar. The guiding hypothesis of the proposed research is that the pools of Cu-binding ligands in wastewater and stormwater are anthropogenic or microbial in origin and possess distinct metal-binding properties compared to the natural ligands present in DOM from surface water systems including lakes and rivers. The specific aims of the research are to: (1) Characterize and identify the pools of Cu-binding ligands present in wastewater and stormwater using a combination of analytical tools including liquid chromatography (LC) followed by parallel inductively coupled plasma mass spectrometry (ICP-MS) and ultra-high-resolution electrospray ionization Fourier transform mass spectrometry (ESI-FT-MS); (2) Develop and validate new Cu chemical speciation models that account for metal-organic complexation in wastewater and stormwater; and (3) Evaluate the impact of metal-organic complexation on Cu removal from wastewater and stormwater using common water treatment sorbents such as activated carbon and biochar. The successful completion of this research has the potential for transformative impact through the generation of new fundamental knowledge and validated models to advance the implementation of chemical speciation-based regulations for controlling the discharge of heavy metals such as Cu into receiving surface water systems while providing critical data and modeling tools to guide the design and operation of sorption-based processes for the removal of heavy metals from wastewater and stormwater. To implement the educational and outreach goals of this project, the Principal Investigators (PIs) plan to leverage their existing partnership with a large Oregon water utility to communicate and translate their research findings into the practice of heavy metals treatment and removal at the company’s operating facilities. In addition, the PIs propose to leverage existing programs at Oregon State University (e.g., NSF funded Louis Stokes Alliances for Minority Participation Program) to recruit undergraduate students from underrepresented groups to work on the project.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.