CSO Treatment

Combined sewer overflow (CSO) treatment is one of the most pressing challenges facing municipalities due to ageing infrastructure. During periods of heavy rainfall or snow melt, the wastewater volume in a combined sewer system exceeds the capacity of most existing treatment plants. The systems are invariably designed to overflow and discharge excess wastewater directly to nearby streams, rivers, or other water bodies thereby causing serious water pollution problems. These overflows contain untreated human and industrial waste, toxic materials, and debris. A high rate treatment process capable of handling suspended solids, dissolved organics, major ions, and microbial contamination is needed. Strong oxidation is proposed as the most likely treatment method for various contaminants and bacteria present in CSOs. The research team will address these issues in novel advanced oxidation reactors (both photon and chemical based) using novel designs and new catalysts to provide large activated catalyst surface area, uniform energy distribution, and efficient mixing inside the reactors.

Specifically, dye-sensitization and chemical doping that utilize solar radiation, and combinations of ozonation, peroxide and ferrate (VI) will be tested and process will be optimized. Photo-stimulated catalysis offers an attractive tool for environmental cleanup but a specific problem associated with commonly used photo-catalysts is the large band-gap energy, which requires artificial light. The success of this technology depends on engineering of electronic bands of the catalyst for paradigm-shift to solar-based photocatalysis that could produce large economic and social benefits. Successful synthesis of chemically modified photocatalyst through band engineering enables the use of sunlight for remediation of environmental pollutants.

Three approaches have been identified to address this issue in our on-going research. The first involves reducing the band-gap through the addition of dopants, thereby permitting light absorption in the visible part of the spectrum. The second strategy involves production of nanoparticles inside polymer templates and cross linking to fix the Fermi level at the solid-solid interface that can harness visible solar spectrum while enhancing efficiency. Thirdly, dye-sensitized photocatalysis in which a dye is adsorbed on to the semiconductor surface which, under visible light illumination, injects electron to the conduction band of semiconductor photocatalyst to initiate the catalytic reaction. In addition, the toxicity and genotoxicity of untreated and treated CSO effluents will be evaluated.