James M. Symons, Principal Investigator
University of Houston
Department of Civil and Environmental Engineering
Houston, TX 77204-4791
Research Grant No. R 817787-01-0
Office of Exploratory Research
Environmental Protection Agency
Washington, D.C. 20460
Small systems frequently have difficulty meeting today's drinking water quality requirements. The overall purpose of this investigation was to develop a treatment process that would be simple enough for small systems to use and would provide a method for disinfection by-product (DBP) control and vigorous disinfection.
Many of the current organic control unit processes have disadvantages: Coagulation and settling produce sludges, air stripping causes air pollution, and adsorption onto granular activated carbon involves regeneration of the adsorbent to renew the adsorbing surfaces. Oxidation, on the other hand, if carried to completion, truly destroys the organic compounds, converting them to carbon dioxide, water, and inorganic ions. Thus, this is an attractive concept.
Traditionally, common oxidants used in water treatment have been chlorine, chloramines, ozone, chlorine dioxide, and potassium permanganate. The development of the use of UV irradiation with oxidants (principally O3) to substantially enhance oxidation and reaction rates for treatment of waterborne inorganic and organic compounds was invented by Garrison, Prengle, and Mauk (1975) and Prengle et al., (1975). Disinfection was included in 1978 (Prengle and Mauk, 1978). The term "advanced oxidation process" (AOP) to describe oxidation processes depending on the creation of the hydroxyl free radical as the oxidant, appeared in the literature in 1988 (Glaze and Kang, 1988 and Aieta et al., 1988).
Since the first work with O3/UV, several different AOPs have been studied. The one chosen for this work was the combination of hydrogen peroxide and ultraviolet light (H2O2/Vis-UV--visible light is produced by the lamp, the importance of this is unknown). This AOP was chosen to avoid the use of ozone, often a difficult substance for small systems to use. Hydrogen peroxide can be purchased as a 30 per cent solution and fed with a metering pump. Because H2O2 is a liquid, completely miscible in water, no mass transfer problems will occur. The mechanism of reaction of this system is based on the direct photolysis of hydrogen peroxide as proposed by Volman (1949):
The hydroxyl radical then participates in numerous steps leading to the partial or complete oxidation of the organic contaminants. In addition, the irradiation may "activate" some of the organic molecules, making them more susceptible to oxidation.
The disappearance of the organic compounds and disinfection by-products presursors, as measured by the removal of TOC, and disinfection by-products, as measured by dissolved organic halogen (DOX) was modeled as a photon-flux-driven-pseudo first-order reaction (now called the Prengle-Shimoda Rate Model). The output of this modeling effort is presented in Equation 2.
For a CFSTR (Figure1):
This phase of the work has resulted in three publications:
Worley, Kevin L. "Oxidation of Natural Organic Matter Using Hydrogen Peroxide and Visible-Ultraviolet Irradiation, MS Thesis, University of Houston, May 1994, 151 pp.
Symons, J. M., Roberts, D.J., Worley, K.L, and Kirkpatrick, C.C., "Evaluation of the H2O2/Vis-UV Advanced Oxidation Process for Controlling DBP Precursors and Providing Disinfection for Small Systems", In: 1994 Annual Conference Proceedings--Water Quality, American Water Works Association, New York, N.Y., June 19-23, 1994, pp. 907-927.
Symons, J. M. and Worley, K.L., "An Advanced Oxidation Process for DBP Control", Journal of the American Water Works Association, 87, (11), 66- 75 (Nov. 1995).
This process studied was effective for destroying both disinfection by-product (DBP) precursors and DBPs themselves, as measured by dissolved organic halogen (DOX).
This phase of the work resulted in two publications:
Kirkpatrick, Carolyn C., "Inactivation of Microorganisms by Hydrogen Peroxide and Ultraviolet Irradiation", MS Thesis, University of Houston, December, 1994, 146 pp.
Kirkpatrick, C.C., Symons, J. M., and Roberts, D. J., Disinfection and Precursor Destruction using the H2O2/Vis-UV Process - Two Treatments in One for Small Systems", In" Proceedings, 1995 Water Quality Technology Conference, American Water Works Association, Denver, Colorado, New Orleans, Louisiana, (November 12-16, 1995) pp. 1967-1984.
A substantial disinfection bonus will result when this process is used for organic destruction.
INTERFERENCE OF BACKGROUND NATURAL ORGANIC MATTER (NOM) WITH ORGANIC SOLVENT OXIDATION
This phase of the work resulted in two publications:
Baker, Charlene M., "Interference of Natural Organic Matter on Oxidation of Volatile Organic Compounds Using Hydrogen Peroxide and Visible-Ultraviolet Irradiation, MS Thesis, University of Houston, December, 1995, 169 pp.
Symons, J. M., Baker, C. M. and Pringle, W. H. Jr., "Influence Of Natural Organic Matter On The Oxidation Of Volatile Organic Compounds Using The Hydrogen Peroxide/Visible-Ultraviolet Irradiation Advanced Oxidation Process" Journal of Advanced Oxidation Technologies, 2, (3), 3388-400 (1997).
Natural organic matter (NOM) interfered with the oxidation of trichloroethane, benzene, and tetrachloroethylene, but not with the oxidation of trichloroethylene and 1,4 dichlorobenzene.
This phase of the work resulted in three publications:
Zheng, M.C. "Changes in Characteristics of Natural Organic Matter During the H2O2 /Vis-UV Photo-Oxidation Process", MS Thesis, University of Houston, August, 1996, 166 pgs.
Symons, J. M. and Zheng, M. C. "Does the H2O2/UV-Vis Process Oxidize Br - to BrO3-?, Journal of the American Water Works Association, 89, (60), 106-109 (June, 1997).
Symons, J. M. and Zheng, M. C. "Behavior Of Natural Organic Matter During Hydroxyl Radical Oxidation" Presented the Natural Organic Matter Workshop, Poitiers, France, September 18, 19, 1996.
The H2O2 /Vis-UV process mineralized about 50 percent of the total organic carbon (TOC) and altered the characteristics of the rest such that it was expected to be less reactive with free chlorine. In addition, bromide was not oxidized to bromate.
This was a successful project, satisfying almost all of the objectives of the original proposal and demonstrating the capabilities for water quality improvement by this advanced oxidation process.
The Principal Investigator wishes to thank Dr. H. William Prengle, Jr., Department of Chemical Engineering, University of Houston, for his assistance in the analysis of these data and Mr. Louis A. Simms Department of Civil and Environmental Engineering, University of Houston for his assistance with the laboratory work.
Aieta, M. E., Reagan, K. M., Lang, J. S. (1988), "Advanced Oxidation Processes for Treating Groundwater Contaminated with TCE and PCE: Pilot-Scale Evaluations," Journal American Water Works Association, 80, (5), 64.
Garrison, R.L., Prengle, H.W. Jr., and Mauk, C.E., (1975), "Method of Destroying Cyanides," U.S. Patent #3,920,547.
Glaze, W. H., and Kang, J-W, (1988), "Advanced Oxidation Processes for Treating Groundwater Contaminated with TCE and PCE: Laboratory Studies," Journal American Water Works Association, 80, (5), 57.
Prengle, H.W. Jr., and Mauk, C.E., (1978), "Ozone/UV Chemical Oxidation Wastewater Process for Metal Complexes, Organic Species and Disinfection," AICHE Symp. Ser., 74, (178), 220.
Prengle, H.W. Jr., Mauk, C.E., Legan, R.W., and Hewes, C.G., (1975) "Ozone/UV Process-Effective Wastewater Treatment," Hydrocarbon Proc., 54 (10), 82.
Volman, D.H., (1949), "The Photochemical Decomposition of Hydrogen Peroxide", J. Chem. Phy., 17, 947.