2024-25 AEESP Distinguished Lecturer

Professor Katz will present two lectures in the 2024-2025 Tour.  Abstracts are below.

Lecture 1: "Translating Molecular Science to Practical Application in Natural Systems and Engineered Processes"

Environmental contamination from anthropogenic activities is often defined by the presence of either legacy or emerging contaminants.  Superfund sites associated with legacy contaminants were the focus of environmental remediation activities in the twentieth century.  Now, "emerging contaminants" have captured the focus of the environmental community.  However the distinction between legacy and merging contaminants is often blurred, especially for metals and metalloids, because once these species enter the environment, they cannot be destroyed and often re-emerge.  The unique properties of elements such as Pb, Hg, Ra, Cd, Zn, Cr, As, Se, B, Li and rare earth elements make them valuable economic resources; demand is growing rapidly and will continue to grow throughout the world.  Their toxicity, fate and transport depend on their concentration and speciation.  The context specific nature of metal ion contamination can also be viewed from an evolutionary perspective. While emerging organic contaminants often derive from the synthesis of novel compounds that provide unique marketable properties, emerging inorganic contaminants often arise from natural resource extraction that yields environmental concentrations above their natural cycles established during evolutionary timeframes. The inability of ecosystems and humans to rapidly adapt to these increased concentrations suggests that caution is needed whenever new elements or higher concentrations of more common metals are introduced or re-introduced into the environment, especially when they are combined with other elements that alter their speciation, electronic structure, or bioavailability.

Significant advances have been made over the past few decades, toward understanding the complex reaction chemistry that controls speciation and ultimately dictates potential treatment and remediation options. Advanced spectroscopic, computational and molecular level tools have been key to identifying speciation and quantifying thermodynamic and kinetic processes. Using tools such as x-ray and vibrational spectroscopy, the structure of ions and interfacial water at interfaces has been revealed. Computational tools have provided validation of molecular structures observed via spectroscopy, confirmed the presence of complexes and ion-pairs at surfaces and within pores, and allowed quantification of thermodynamic parameters of processes such as sorption and precipitation. The translation of these results to predict contaminant fate and transport in natural systems has relied on macroscopic or thermodynamic based models such as surface complexation models for oxide minerals or the Donnan-Manning model for membrane systems. The continual refinement of these models is often guided by molecular level insights that provide more accurate descriptions of sorption, ion exchange and precipitation processes and more detailed descriptions of the electrical double layers present at charged interfaces. In this seminar, we will explore several examples in which molecular level insights from spectroscopic and/or computational studies have been used to guide modeling of metal ion sorption in water treatment processes, predict ion-pairing in membrane systems, and describe metal(oid) processes in contaminated sediments in mining impacted lakes. Through these examples, we will demonstrate how increased understanding at the molecular level can guide contaminant remediation and treatment options.

Lecture 2: "Drinking Water Quality in Rural Alaska: Addressing Socioeconomic Challenges from Molecular Level Insights"

Providing water services in rural communities is a complex endeavor. Intertwined environmental, economic, and social factors can create barriers to reliable water services in communities. For instance, melting permafrost can threaten the structural integrity of infrastructure, or a lack of trained workforce can lead to system neglect. Geographic isolation of communities can lead to extreme challenges for construction and maintenance. As a result, water utilities serving these communities often incur violations either due to water quality or insufficient monitoring. Thousands of homes in rural Alaska still today do not have piped drinking water to their homes. In many cases, water haulers deliver water to home storage tanks in one to four week intervals. Moreover, the aesthetic quality of the water (brown colored with chlorine odor) delivered to these communities has been challenged, and many residents choose to drink from alternative water sources (i.e., rainwater, bottled water, snowpack). Utilities also struggle to recruit and retain qualified staff to operate treatment processes that require higher levels of certification such as oxidation and greensand filtration.

The most common method of iron and manganese removal in Alaska is a continuous regeneration manganese greensand process. Greensand consists of a manganese oxide coating on glauconite, an iron rich member of the illite clay mineral group. The greensand filtration process often operates in a continuous regeneration mode using permanganate to oxidize soluble iron and manganese to insoluble species (MnOx(s) and Fe(OH)3(s)) that are removed by greensand media alone or by a combination of anthracite and greensand. While greensand filtration processes can be effective at removing iron, manganese and arsenic, optimization of the process is challenging due to the complex interactions associated with near simultaneous oxidation, adsorption and precipitation processes. For example, iron oxidation leads to formation of amorphous iron hydroxide solids which can either co-precipitate or adsorb co-oxidized arsenic species. The presence of arsenic, in turn, can impact the structure and morphology of the iron hydroxide solids formed as well as overall process efficiency. Thus, while the process may seem relatively straight-forward, there is a need to develop a more complete understanding of the process and controlling mechanisms to establish clear operational guidelines for remote communities.

This presentation focuses on water quality results from a recent study of drinking water in homes that receive hauled water from a groundwater sourced water treatment system in the Yukon-Kuskokwim region of Alaska. The first part of the talk will address the challenges associated with operating and delivering water in these remote communities, the water quality challenges experienced, and the performance of the drinking water processes. The second part of the talk will explore mechanisms associated with contaminant removal in precipitating systems. Finally, the presentation will explore the role of climate change in delivering infrastructure in the Arctic and what climate adaptation looks like in communities that are on the melting tundra with regard to water delivery.