Research & Facilities

Hexavalent Chromium Occurrence and Treatment in Drinking Water


Chromium(VI), known as hexavalent chromium, is a highly toxic and soluble compound that has been widely observed in groundwater. It enters groundwater through improper industrial waste disposal as well as geological weathering of naturally occurring chromium-containing aquifer minerals. As a new drinking water standard specific to chromium(VI) is upcoming in California and being considered by US EPA, it poses great challenges to Californian water systems to upgrade treatment to meet the new regulation. Available water treatment technologies normally transform soluble chromium(VI) to particulate chromium(III) before removing the solids. Albeit that, these treatment processes are not efficient to achieve the low concentrations that will be required. Subsequently, in water distribution piping systems, residual chromium(III) and chromium(VI) can participate in multiple reactions that involve heterogeneous chemical oxidation, reduction, adsorption, and co-precipitation. However, these chemical processes that eventually impact chromium(VI) levels in finished drinking water are not understood yet. Our research seeks to advance the mechanistic understanding of chromium(VI) conversion and formation pathways from water resources to treated drinking water, as well as to develop new reductive treatment processes that can minimize hazardous residual disposal. By applying interfacial process characterization and electrochemistry tools, we hope to advance the overall infrastructure for resource management and water quality research. 


Advanced Oxidation and Radical-driven Processes: Enhance Water Quality and Quantity in Response to Droughts and Climate Change


Water shortage has become a global crisis. Restoration of contaminated source water and reuse of treated wastewater effluent are the two promising solutions to address the water crisis. Advanced oxidative treatment for groundwater remediation and wastewater treatment has gained increasing attentions in recent years due to its capacity to remove contaminants of emerging concerns such as flame retardants and personal care products. However, little is known about the nature of oxidation by-products and their toxicological effects. Furthermore, traditional oxidants are usually non-selective and have low treatment efficiencies. We are interested in applying sulfate radical as a new and more efficient oxidant for groundwater remediation and water reuse applications. The collaborative research will investigate the treatment efficiency of using sulfate radical by using a series of emerging contaminants, identify the unique oxidative transformation pathways and the degradation by-products of these pollutants, and examine the toxicity of the observed by-products using various bioassay-directed screening methods. This seed project will empower the PIs with enough preliminary data towards a fundamental understanding of the reactions of sulfate radical in groundwater and treated effluent that can be used to optimize treatment, predict the rate of contaminant transformation and prevent the release of toxic products of incomplete oxidation of emerging contaminants in water treatment processes.