(formerly ENERGY AND ENVIRONMENTAL ENGINEERING, INC.)
(PhotoCAT Process)
The PhotoCAT process photochemically oxidizes organic compounds in wastewater using hydrogen peroxide, a chemical oxidant, ultraviolet (UV) radiation, and a photocatalyst. The photochemical reaction has the potential to reduce high concentrations (200,000 or more parts per million [ppm]) of organics in water to nondetectable levels. The energy from UV radiation is predominantly absorbed by the organic compound and the oxidant, making both species reactive. The process can be used as a final treatment step to reduce organic contamination in industrial wastewater and groundwater to acceptable discharge limits.
The existing bench-scale system treats solutions containing up to several thousand ppm of total organic carbon at a rate of 3 gallons per minute. The bench-scale system consists of a photochemical reactor, where oxidation occurs, and associated tanks, pumps, and controls. The UV lamps are high-intensity lamps that penetrate the wastewater more effectively. The portable, skid-mounted system's design depends on the chemical composition of the wastewater or groundwater being treated.
Typically, the contaminated wastewater is pumped through a filter unit to remove suspended particles. Next, the filtrate is mixed with stoichiometric quantities of hydrogen peroxide. Finally, this mixture is fed to the photochemical reactor and irradiated. The overall reaction is as follows:
CaHbX + [2a + 0.5(b - 1)]H2O2 hv aCO2 + [2a + (b - 1)]H2O + HX
where CaHbX represents a halogenated contaminant in the aqueous phase. Reaction products are carbon dioxide, water, and the appropriate halogen acid. Reaction kinetics depend on (1) contaminant concentration, (2) peroxide concentration, (3) irradiation dose, and (4) radiation spectral frequency.
The PhotoCAT process treats industrial wastewater and groundwater containing organics at concentrations up to several thousand ppm. Destruction efficiencies greater than two orders of magnitude have been obtained for chlorobenzene, chlorophenol, and phenol, with low to moderate dose rates and initial concentrations of 200 ppm. Destruction efficiencies of three orders of magnitude have been demonstrated on simulated industrial waste streams representative of textile dyeing operations, with higher dose rates and an initial concentration of 200 ppm.
Studies of the PhotoCAT process under the SITE Emerging Technology Program are complete, and the technology has been invited to participate in the SITE Demonstration Program. The Emerging Technology Report (EPA/540/SR-92/080), Emerging Technology Bulletin (EPA/540/F-92/004), and Emerging Technology Summary (EPA/540/SR-92/080) are available from EPA.
Work involving the on-line production of oxidants and the effectiveness of the photocatalytic substrate is underway under funding from EPA Small Business Industry Research Phase II and Phase I awards.
Representative results from recent trials using the PhotoCAT process are summarized in the table below. Results are shown as the electric energy dose per gram-mole of initial contaminant to cause one decade of contaminant destruction.
Contaminant* |
Dose (kW-hr/ |
|---|---|
| Chlorobenzene | 7 |
| Trichloroethene | 5 |
| Trichloroethane [500] | 1 |
| Tetrachloroethene | 6 |
| 1,1,1-Trichloroethane | 33 |
| 1,1,1-Trichloroethene [1,000] | 7 |
| Benzene, toluene, ethylbenzene, & xylene | 5 |
|
|
| Reactive Black Dye 5 | 26 |
| Direct Yellow Dye 106 | 103 |
| Direct Red Dye 83 | 31 |
| Reactive Blue Dye 19 | 50 |
|
|
| 1-Chloronaphthalene [15] | 27 |
| Ethylene, diamine, & triacetic acid | 17 |
| Methanol | 3 |
|
|
| Textile waste (sulfur & indigo dyes) [740] | 11 |
| Textile waste (fiber reactive dyes) [270] | 7 |
| Chemical waste (formaldehyde & thiourea) [8,200] | 1 |
| * all are 100 parts per million, except as noted | |
| ** kilowatt-hour per gram-mole per decade |
|
The technology has been improved since the EPA reports were published. These improvements include (1) using the UV lamp as the energy source; (2) improving the photochemical reactor design; (3) improving the lamp design, including lamp intensity and spectral characteristics; and (4) fixing the catalyst.
A cost-competitive PhotoCAT system can be designed and built to treat industrial wastewater with contaminant levels of 10 to 10,000 ppm.
EPA PROJECT MANAGER:
Ronald Lewis
U.S. EPA
National Risk Management Research Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7856
Fax: 513-569-7105
TECHNOLOGY DEVELOPER CONTACTS:
James Porter or John Roll
UV Technologies, Inc.
P.O. Box 410185 or 410186
East Cambridge, MA 02141-0002
617-666-5500
Fax: 617-666-5802