» Foundation Research
-
Membrane Science and Processes
Thrust 1 was driven by the need to develop a mechanistic understanding of aqueous-membrane interfaces and solute-surface interactions. It encompassed the synthesis of tailored or active materials that allowed the selective removal of a wide range of contaminants. Targeted species included trace organic contaminants such as pesticides, industrial by-products , inorganic species such as toxic oxyanions (nitrate, perchlorate, arsenate, selenate) and heavy metals, pathogens (e.g., Cryptosporidium and Mycobacteria), and the salts and organic matter that are in brackish groundwaters, ocean water and wastewater. The projects in this thrust deal with topics such as the mechanism of transport in nanometer diameter channels; development of new polymeric and ceramic membranes; and the development of hybrid membrane water quality control systems for economical purification of contaminated waters from a variety of sources. Researchers involved in this thrust will interface with the catalysis group to develop catalytic membrane systems.
-
Adsorption Science and Processes
Thrust 2 aimed at furthering the science of adsorption, development of new adsorbent materials, and adsorption processes for removing both organic and inorganic contaminants from water. This Thrust included synthesis of greatly improved carbon and ion exchange fibers, activated carbon granules, and other adsorbents tailored to selectively adsorb a wide range of trace contaminants, resulting in contaminant levels well below current EPA standards. The efforts in this Thrust attempted to scale-up these processes for use by manufacturing and drinking water treatment industries. Design of systems for point-of-use were also pursued for remote water purification needs including, communities, villages and homes.
-
Chemical Redox Science and Processes
This thrust focused on oxidation-reduction science and processes that are important in the catalytic destruction of contaminants and the inactivation of pathogens. One component dealt with the design of catalytic systems that convert toxic contaminants such as selected oxyanions (nitrate, perchlorate, etc) into more benign forms. Reductive catalytic treatment using supported bimetallic catalysts was investigated. Oxidative catalytic destruction of water contaminants was also investigated. Systems of particular interest included metal oxide oxidation and hydrolytic catalysts supported on high surface area substrates. The recently discovered TiON activated by visible light may be the most versatile and powerful oxidizing agent known and merited detailed evaluation in the program. The oxidative catalysts may also be effective in killing pathogenic microorganisms, and if so, these materials could be highly effective in point-of-use treatment devices. This possibility also received careful attention.
A second component of this thrust addressed disinfection by developing and evaluating new bactericides including novel configurations of metals and nanostructured metal oxides. The mechanisms by which the metal destroys the bacteria and incorporation of this material into process designs was also studied.
-
Biochemical Processes
Thrust 4 encompassed the evaluation of membrane materials under actual and simulated treatment conditions for the purpose of understanding and controlling the important phenomenon of fouling of membranes. One focus was the science of membrane fouling, and on the development of membranes resistant to biofouling. Initial tasks included the quantification of physicochemical interactions between various membranes and chemical and biological foulants, the in situ study of substratum-biofilm interaction, and the improvement of state-of-the-art membrane materials that are resistant to fouling and tolerant of anti-fouling agents. The development of biofilms at the surface of membranes and polymeric surfaces was also studied. In the course of these studies, fundamental issues related to the response of bacteria to surface properties, such as gene induction in response to membrane surface structure, microbial adhesion and community structure, and the transport of contaminants and by-products across the membranes, were addressed.
A second aspect of this thrust was the membrane bioreactor program. Biofile-substrata interactions were studied at the surface of ultrafiltration membranes used in anaerobic bioreactors treating domestic and agricultural wastewaters. Membrane systems that remove hydrogen for energy recovery were explored for energy sustainability. Chemical and biological factors that influence surface colonization and biodegradation (aerobic and anaerobic) of wastewater contaminants, growth kinetics, stability and physiology of biofilms were examined. In conjunction with Thrust 1 (above) activities, trafiltration membranes that retain biomass without fouling, especially under anaerobic conditions, and membranes that separate gases (hydrogen, methane) from water, were synthesized and evaluated.
-
Active Aqueous Transport Processes
Thrust 5 investigated the transport of ionic and molecular species in water treatment systems being developed by The WaterCAMPWS that employed new classes of active materials. In order to develop these revolutionary materials and systems, the physico-chemical processes that occur at the aqueous interface with ions and molecules needed to be better understood at a fundamental level. These physico-chemical processes include the energetics of active transport in confined nanopores, the interaction of species in the presence of thermal, chemical, and electrical fields and gradients, and the molecular mechanisms of transport of species in aqueous media in contact with charged and neutral moieties on materials being synthesized in the Center. As such, participants in Thrust 5 were actively involved in synthesizing materials and developing systems to achieve active transport, and interacted with other Thrust participants to relate these developments to water treatment.
Thrust 5, therefore, included a number of components that support active aqueous transport processes. These projects involved developing the experimental and theoretical tools to better understand the transport of species in confined nanopores, synthesizing molecules and material systems for active transport and separation of ionic and supramolecular compounds, and both theoretical and experimental investigation of active transport in material systems being developed for water treatment. Researchers participating in these projects brought together expertise from a wide range of basic disciplines, including computational techniques and advanced spectroscopy, instrumentation, system design, and material fabrication.
