Combination of Chlorine-Free Electrolytic and Photochemical Methods for Sterilization of Contaminated WatersEPA Contract Number: EPD11052
Title: Combination of Chlorine-Free Electrolytic and Photochemical Methods for Sterilization of Contaminated Waters
Investigators: Barashkov, Nikolay
Small Business: Micro-Tracers Inc.
EPA Contact: Manager, SBIR Program
Project Period: March 1, 2011 through August 31, 2011
Project Amount: $73,433
RFA: Small Business Innovation Research (SBIR) - Phase I (2011) RFA Text | Recipients Lists
Research Category: SBIR - Water and Wastewater , Small Business Innovation Research (SBIR)
Effective electrolytic sanitizing of contaminated waters using chloride requires a relatively high concentration of the elemental chlorine and hypochlorides. This requires a high concentration of chloride salt (higher than 0.15%). At such a concentration, chloride ions cause corrosion of various bimetal connections found in water plumbing systems, such as water distributors, cooling towers, etc. Replacement of chloride anions with anions of phosphates, nitrates, sulfates, and benzoates or carbonates that do not cause corrosion would be advantageous in reducing the cost of equipment. In addition, other problems associated with using chlorine in wastewater treatment include unfavorable odor, ineffectiveness when used alone against resistant microorganisms such as Cryptosporodium parvum, and occasional failure to meet regulatory standards.
This project relates to advanced oxidation disinfecting processes, and more particularly, to the combined use of singlet oxygen and electrochemical sterilization utilizing non-chloride electrolytes to kill non-pathogenic and pathogenic bacteria in contaminated water. The electrolytic process will generate free radicals and changes in redox potential; the photochemical reaction of triplet oxygen with excited molecules of insoluble form of fluorescent dyes will generate singlet oxygen.
Micro-Tracers plans to provide experimental proof that singlet oxygen generated during irradiation of the water-insoluble form of photosensitizer (Al-salts of fluorescent dyes, deposited on the silica gel and dispersed in polymer coating) has a significant sanitizing effect on the water contaminated with non-pathogenic bacteria such as E. coli B and pathogenic bacteria such as S. typhimurium.
The sanitizing effect against non-pathogenic and pathogenic bacteria provided by AC electrolytic processes that produce oxidants in chloride-free water solutions will be investigated in media such as phosphate buffer, ammonium sulfate, sodium carbonate, sodium nitrate, sodium sulphate, sodium dihydrogen phosphate, trisodium phosphate and calcium benzoate at low current (from 0.15 to 1.2 A), relatively low current densities (from 45 ma/cm2 to 360 ma/cm2), and initial voltage demand of 20-80 volts.
Micro-Tracers plans to demonstrate that the combination of the two sterilization methods—namely, the singlet oxygen generation and chlorine-free electrolytic process—provides a more efficient sanitizing effect against non-pathogenic and pathogenic bacteria than either of the two individual methods. The mechanism of the sanitizing effects of the singlet oxygen generation, as well as the chlorine-free electrolytic method, will be investigated, and the nature of intermediate products (free radicals, peroxides, etc.) will be identified.
Potential commercial application of a new method includes a sterilization of poultry rinse water contaminated with pathogenic and non-pathogenic bacteria.