Research Interests and experience

Characterization of natural organic matter (NOM) and effluent organic matter (EfOM)

Many of my projects have been concerned with NOM characterization in diverse water sources, effects of water treatment on its reactivity and NOM interactions with halogens leading to the formation of disinfection by-products (DBPs). This research resulted in the development of new tools to address NOM transformations, for instance via differential spectroscopy. Another issue prominent in my research is the characterization of NOM behavior in protonation/deprotonation and metal complexation reactions. Lately my research has addressed applications of size exclusion chromatography to characterize of NOM and EfOM, examination of EfOM alteration by ozonation and other oxidation processes and EfOM roles in the degradation of trace-level organic contaminants.

Formation of disinfection by-products and degradation of trace-level organic pollutants (pharmaceuticals and personal care products)

A considerable part of our research has been concerned with the elucidation of pathways of formation and breakdown of halogenated DBPs. My recent activities in the area have been centered on the development of formal models of the formation of bromine- and nitrogen-containing DBPs. We have been actively engaged in studies concerned with the transformations of pharmaceuticals and personal care products (PPCPs) caused by ozonation, advanced oxidation processes and halogenation. This area of my research is expanding rapidly.

Corrosion and metal release in drinking water

Corrosion is a challenging issue closely associated with long- and short-term stability of water distribution systems and water quality in them. My research has addressed the role of NOM and other water chemistry components (chlorine/chloramine, pH, carbonate, phosphate) in corrosion of iron, copper and lead-containing materials, novel approaches to quantify corrosion rates and metal release in drinking water. Experimental methods that we use in these studies include electrochemical (corrosion potential dynamics, cyclic voltammetry, potentiodynamic scans, rotating ring/disc electrode), structural (SEM, XRD, EXAFS) and analytical (ISE, ICP/MS) techniques.

Environmental chemistry of heavy metals

My involvement in corrosion research has lead to a considerable interest in the environmental chemistry of lead and copper, that is to say in their complexation with NOM and other ligands, formation of solid phases controlling their solubility and numerical modeling of these processes. I have also been involved in projects concerned with the environmental chemistry of arsenic, uranium, lanthanides, proxies for radioactive cesium and strontium and treatment of drinking water and wastewater containing these and other metals. Our recent studies have addressed the accumulation of multiple heavy metals in drinking water distribution systems.  

Environmental spectroscopy and on-line methods to characterize water quality

My education and overall research/teaching experience are strongly influenced by optical spectroscopy and associated methods. This has lead to the exploration of differential absorbance methods that are valuable in studies of complex entities such as NOM and EfOM. I also have profound interest in fluorescence methods ranging from conventional 2D scans to deconvolution of 3D excitation-emission matrixes and time-resolved methods. Some of these approaches developed in our group are being implemented for on-line water quality monitoring (e.g., in several sites in Australia and New Zealand). I am interested in other spectroscopic techniques, especially in X-Ray Absorbance Spectroscopy that is indispensable for ascertaining the redox and structural state of heavy metals in environmental systems. Our EXAFS research has been carried with the help and support from Prof. Frenkel. Exploration that employs these methods can be enhanced by quantum-mechanical modeling that has been carried by Prof. Kuznetsov’s group for some of the systems of interest to us.

Environmental electrochemistry

Electrochemical methods can deliver very interesting data for a variety of situations, notably in studies concerned with corrosion of heavy metals and their release, formation of unstable intermediates and redox transformations of various organic contaminants. We have used these techniques to explore the formation of As(IV) and Pb(III) transient species but I feel that there is still a lot to be done there. Electrochemical methods can also perform very well in drinking water and wastewater treatment and help degrade a variety of contaminants. I have maintained strong interest to analytical and treatment applications of electrochemistry, and hope to expand this are of my research in the future.

Recently completed and current projects

Methods for the Detection of Residual Concentrations of Hydrogen Peroxide in Advanced Oxidation Processes (completed)

(with Dr. Phil Branhuber, HDR Inc.)

WateReuse Foundation

Effects of Change of Disinfectants on Release of Metals in Drinking Water (completed)

(with Glen Boyd and Steve Reiber, HDR Inc. and Cadmus Group)

Water Research Federation 

Control of Accumulation of Inorganic Contaminants in Distribution Systems (completed)

(with Andrew Hill and Melinda Friedman, Confluence Engineering and Prof. Richard Valentine, University of Iowa)

Water Research Federation

Fundamental Mechanisms of Lead Oxidation: Effects of Chlorine, Chloramine and Natural Organic Matter on Lead Release in Drinking Water (completed)

National Science Foundation

Equipment for Analyses for Endocrine Disruptors, Pharmaceuticals and Personal Care Products (completed)

The Murdoch Foundation

Impacts of Blending Santa Cruz Water on Lead and Copper Release and on Red Water (completed)

(with Prof. Ferguson)

City of Santa Cruz/State of California

Effects of Desalinated Water and Its Blends with Conventionally Treated Water on the Corrosion of and Metal Release from Iron, Copper- and Lead-Containing Materials (current)

National Science Foundation

Use of UV and Fluorescence Spectra as Surrogate Measures for Disinfection and Contaminant Oxidation in the Ozone/Peroxide Advanced Oxidation Processes (current)

(with Prof. Shane Snyder, University of Arizona and Dr. Dan Gerrity, South Nevada Water Authority)

WateReuse Federation

Use of On-line Surrogate Parameters for Rapid Hazard Detection and Improved System Performance (current)

(with Dr. Chris Chow and Mary Drikas, Australian Water Quality Centre)

Water Quality Research Australia

(This project is being carried out in Adelaide, South Australia)