Perchlorate Removal Technologies
Government, Industry Committed to Sound Science and Public Safety
In response to finding perchlorate at low levels in water, private industry, in cooperation with the federal government, developed and is currently using sophisticated new technologies for removing perchlorate from surface and groundwater supplies.
In addition, efforts to prevent perchlorate from seeping into groundwater and other water sources are ongoing. Barriers, wells, pipes and water treatment facilities are among the techniques being used in these aggressive efforts.
There currently are two major technologies used to treat large volumes of water that contain perchlorate: ion exchange and biological treatment. Other technologies are currently under development, including membrane filtration and electrodialysis.
Ion exchange technology uses a resin to absorb perchlorate and remove it from water. The contaminated water is pumped through a system containing resin "beds," which are two to six feet in diameter and one to six feet high. Negatively charged perchlorate is captured on the positively charged resin, releasing harmless chloride (a component of table salt) in its place and affording the opportunity for safe and appropriate disposal.
Biological treatment is a process that uses microorganisms to break down perchlorate into other components. In this process, water is treated in a tank, using microorganisms, or in the ground, using native organisms. Small amounts of carbon sources, such as alcohol or corn syrup, are also placed in the water. The microorganisms then convert the perchlorate and carbon into two primary components: carbon dioxide and chloride.
This technology involves forcing water through a semiporous polymer membrane. One technique is called reverse osmosis. In reverse osmosis, artificial pressure is applied on one side of the membrane, thus forcing water to migrate through the membrane wall, leaving perchlorate and most other dissolved salts behind.
Nanofiltration is a similar technique using membranes with slightly larger pores. Work at the Metropolitan Water District of Southern California has yielded some positive results regarding this type of perchlorate treatment. However, fouling of the membrane filters remains a concern for both reverse osmosis and nanofiltration technologies.
Electrodialysis (currently under development) passes water through different membranes while exposing it to an electric field. The electric field separates the perchlorate from the stream of treated water. The perchlorate-containing brine is then appropriately discarded.
Case Studies: Where and How Technologies Are Being Used