Pilot-Scale Cross-Flow Pervaporation System
ZENON ENVIRONMENTAL INC.
(Cross-Flow Pervaporation System)
TECHNOLOGY DESCRIPTION:
The ZENON Environmental Inc. (ZENON), cross-flow pervaporation technology is a membrane-based process that removes volatile organic compounds (VOC) from aqueous matrices. The technology uses an organophilic membrane made of nonporous silicone rubber, which is permeable to organic compounds but highly resistant to degradation. The composition of the membrane causes organics in solution to adsorb to it; the organics then diffuse through the membrane by a vacuum and condense into a highly concentrated liquid called permeate. The permeate separates into aqueous and organic phases. The organic phase can either be dis-posed of or sent off site for further processing to recover the organics. The aqueous phase is sent back to the pervaporation unit for treatment.
In a typical field application, contaminated water is pumped from an equalization tank through a prefilter to remove debris and silt particles, and then into a heat exchanger that raises the water temperature to about 165 °F (75 °C). The heated contaminated water then flows into the pervaporation module. Organics and small amounts of water are extracted from the conta-minated water, and treated water exits the pervaporation module and is discharged from the system.
The extracted organics and small amount of water are called permeate. As the permeate exits the membranes, it is drawn into a condenser by the vacuum, where the organics and any water vapor are condensed. Because emissions are vented from the system downstream of the condenser, organics are kept in solution, thus minimizing air releases.
The condensed organic materials represent only a very small fraction of the initial wastewater volume and may be subsequently disposed of at significant cost savings. This process may also treat industrial waste streams and recover organics for later use.
WASTE APPLICABILITY:
Pervaporation can be applied to aqueous waste streams such as groundwater, lagoons, leachate, and rinsewaters that are contaminated with VOCs such as solvents, degreasers, and gasoline. The technology is applicable to the types of aqueous wastes treated by carbon adsorption, air stripping, and steam stripping.
STATUS:
This technology was accepted into the SITE Emerging Technology Program in January 1989. For further information on the pilot-scale system, refer to the profile in the Emerging Technology Program section (completed projects). Based on results from the Emerging Technology Program, ZENON was invited to demonstrate the technology in the Demonstration Program. A pilot-scale pervaporation system, built by ZENON for Environment Canada's Emergencies Engineering Division, was tested over a 2-year period (see photograph on previous page). During the second year, testing was carried out over several months at a petroleum hydrocarbon-contaminated site in Ontario, Canada.
A full-scale SITE demonstration took place in February 1995 at Naval Air Station North Island in San Diego, California, at a former waste disposal area. Organics are the primary ground-
water contaminant, and trichloroethene (TCE) was selected as the contaminant of concern for the demonstration. The Demonstration Bulletin (EPA/540/MR-95/511) is available from EPA.
The demonstration was conducted as a coopera-tive effort among EPA, ZENON, the Naval Environmental Leadership Program, Environ-ment Canada, and the Ontario Ministry of Environment and Energy.
DEMONSTRATION RESULTS:
Preliminary demonstration results, based on field gas chromatograph data, indicate that the ZENON pervaporation system was about 98 percent effective in removing TCE from groundwater. The system achieved this removal efficiency with TCE influent concentrations of up to 250 parts per million at a flow rate of 10 gallons per minute (gpm) or less. Treatment efficiency remained fairly consistent throughout the demonstration; however, at a flow rate near 2 gpm, the treatment efficiency decreased during the 8-hour sampling run due to mineral scaling problems.
FOR FURTHER INFORMATION:
EPA PROJECT MANAGER:
Ronald Turner
U.S. EPA
National Risk Management Research
Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7775
Fax: 513-569-7620
TECHNOLOGY DEVELOPER CONTACT:
Philip Canning
ZENON Environmental Inc.
845 Harrington Court
Burlington, Ontario, Canada
L7N 3P3
905-639-6320
Fax: 905-639-1812