Research
Research Interest
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Sustainable water and wastewater treatment and management
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Development of assessing and predicting tools for water treatment technologies
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Innovative water and wastewater treatment technologies for energy saving and harvesting
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Systematic and integrated understanding of water and wastewater reuse
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Application of computational chemistry and molecular modeling
Overall Picture of Research
Dr. Minakata's group aims to develop and manage sustainable technologies for water and wastewater treatment and energy harvesting. By 2050, 70% of the global population is expected to live in a city. Global urbanization will continue, and this will require many countries including the U.S. to reinvest/redesign infrastructure systems towards sustainable urban development. The sustainable development seeks to 1) reduce environment impacts and 2) improve impacts to human health. When we look at water infrastructure systems in the U.S., approximately 4% of total electricity consumption is for the water and wastewater treatment sector. However, a water-energy nexus indicates that there are significant contributions of consumptions of water and energy and environmental impacts from other sectors. As we increase de facto and planned water reuse, there will be critical needs that will include: 1) sustainable technology development for water and wastewater treatment and energy harvesting and 2) management of water and energy by considering both infrastructure systems and socio-economic environmental aspects.
Three Major Areas of Research
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Development of assessing and predicting tools for water treatment technologies
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Innovative water/wastewater treatment technologies for energy saving and harvesting
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Systems approach and integrated understanding of water/wastewater reuse
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Development of Assessing and Predicting Tools
(Water reclamation, human health, and environmental ecology)
When we understand scientific fundamental principles of chemical physical phenomena in natural, biological, and engineered systems, comprehensive tools are useful to 1) design the systems, 2) evaluate and 3) predict their performances. Experimental observations coupled with theoretical evaluations enable us to develop those comprehensive tools. We will use the computational tools to predict a fate of various specifies in natural, biological and biomedical, and engineered systems.
1.1 Coupling Experimental and Theoretical Molecular-Level Investigations to Visualize the Fate of Degradation of Organic Compounds in Aqueous Phase Advanced Oxidation Systems
The lack of a holistic management plan combined with uncertainty about the adverse human health and ecological impacts of trace amounts of known and emerging organic compounds have raised public concerns about water. These issues also present major challenges to next generation water treatment utilities dealing with de facto and planned wastewater reuse. Advanced oxidation processes that produce highly reactive hydroxyl radicals are promising technologies to control trace amounts of organic compounds. Although the initial fate of hydroxyl radical induced reactions with diverse organic compounds have been studied, the mechanisms that produce intermediate-radicals and stable-byproducts are not well understood. Significant barriers remain in our understanding of complex multi-channel elementary reaction pathways embedded in peroxyl radical bimolecular decay that produce identical intermediate-radicals and stable-byproducts.
Known and Proposed General Reaction Pathways in AOPs
Elementary Reaction Pathways for Reaction of HO* with Generic Form of RCH3
1.2 Fate of Dissolved Organic Matter in the Aqueous-phase Ultraviolet (UV) and UV-based Advanced Oxidation Systems
With a potential adverse impact of diverse trace organic contaminants to human health and ecological systems, the removal of those contaminants from wastewater discharge is an urgent task. Ultraviolet (UV) based advanced oxidation processes (AOPs) are promising technologies for the removal of these contaminants owing to the production of highly reactive active radical species that have the ability to degrade a wide range of organic contaminants. However, the removal efficiency of trace organic contaminants is greatly hindered by other water constituents including alkalinity, other inorganic elements, and background dissolved organic matter (DOM). While the scavenging effects of DOM are well known, little is known about the radicals-induced transformation of complex mixture of DOM and the impact on the performance of AOPs.
1.3 Photochemical Fate of Dissolved Amino Acids in Natural Aquatic Environment
The rare abundance of free amino acids (FAAs) in freshwater systems and the large energy cost of synthesis make FAAs essential to aquatic biota. The initial photochemical transformations of various FAAs have been investigated; however, subsequent radical reactions control their fate in freshwater systems and are poorly understood. The proposed investigation will use ab initio and density functional theory (DFT), quantum mechanical (QM) methods to predict the photochemical fate of FAAs in freshwater systems.
1.4 Predicting the Rejection of Organics Through Reverse Osmosis (RO) Membrane for Potable Reuse
Reverse osmosis (RO) is a membrane technology that separates dissolved species from water. RO has been applied for the removal of chemical contaminants from water and is employed in wastewater reclamation to provide an additional barrier to improve the removal of trace organic contaminants. The presence of a wide variety of influent chemical contaminants and the insufficient rejection of low molecular weight neutral chemicals by RO calls for the need to develop a comprehensive model that predicts the rejection of various organic compounds in RO.
2. Innovative Water/Wastewater Treatment Technologies for Energy Saving and Harvesting
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Advanced oxidation processes
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Self-sustained water/wastewater treatment technology for high strength industrial wastewater
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Integrated approach for water/wastewater treatment and hydrogen generation using catalysts
3. Systems Approach and Integrated Understanding of Water/Wastewater Reuse
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Sustainable and resilient water/wastewater reuse
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Wastewater treatment technology development for direct potable use
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Interdisciplinary understanding of water/wastewater reuse for direct potable use
3.1 Household Food-Energy-Water (FEW) Metabolism
Total water use in the U.S. has decreased since 1980, primarily due to increased efficiencies in irrigation and thermoelectric cooling. This has been accompanied by a shift in water resources from low-valued to high-valued uses, all resulting in a sharp increase in the economic productivity of water at the national level. However, threats to aquatic biodiversity remain ubiquitous due to factors such as consumptive water loss, nonpoint source pollution, river fragmentation, and hydroperiod disruption. In some areas with rapidly growing urban centers, droughts have disproportionately affected surrounding rural economies; while in areas facing urban decline, reductions in water use coupled with deferred infrastructure maintenance have led to financial distress for utilities and, in some cases, even public health crises. While residential water use consumes more water than any other customer sector in most US cities, household interventions in food-energy-water (FEW) nexus are not well understood.