Calgon Carbon Is Set To Use Combined UV/Ion Exchange System On Groundwater
Calgon Carbon Corp. (Pittsburgh, PA) has been awarded a contract from the La Puente Valley County Water District in Southern California to supply an ISEP ion-exchange system to remove perchlorate, and use its Rayox UV tower to destroy N-nitrosodimethylamine (NDMA) in water from three local wells. The wells have been shut down since 1997, when the contaminants were first detected. The contract is valued at over $3.0 million. ISEP has been used commercially before, but this is the first application for perchlorate removal.
The ISEP system utilizes Calgon Carbon's patented, continuous ion-exchange contactor. Calgon acquired the technology when it bought Advanced Separation Technologies, a Lakeland, FL, technology firm, in 1997. The Rayox Tower, operating at 1-360 kW, employs Calgon Carbon's proprietary, medium-pressure, ultraviolet (UV) lamps to destroy NDMA onsite. The two systems will treat approximately 2,500 gpm of water. The ISEP will reduce the concentration of perchlorate from 200 ppb to less than 5 ppb, while the Rayox Tower will reduce the NDMA from 900 parts per trillion (ppt) to less than 5 ppt.
The ISEP system features a rotary wheel with compartments for treating water, draining and then regenerating ion-exchange beds, such that the process runs continuously. It is also used as a production-scale chromatograph to purify lysine and corn syrup. Rayox (see figure), another proprietary Calgon technology, is configured either as a straight photolysis unit, or can be combined with catalysts or reactants such as ozone for more-rapid organic removal. In addition to removing perchlorate and NDMA, the Calgon systems will also reduce nitrates and sulfates in the treated water.
Rayox, another proprietary Calgon technology.
Perchlorate, which prevents proper functioning of the thyroid gland, is a component of rocket fuels, fireworks, and explosives, says Calgon Carbon. NDMA, a suspected carcinogen, is a byproduct of liquid rocket fuel combustion and has been found as a by-product in the manufacture of rubber products and certain chemical intermediates. Improved analytical testing methods in recent years have permitted the detection of the contaminants in low concentrations in drinking water.
Calgon Carbon has been utilizing its UV technology to treat NDMA since 1991. However, no method for removing perchlorate from drinking water had been demonstrated until the ISEP successfully removed perchlorate in trials at two separate sites in the Greater Los Angeles Area last year.