There are various options available for removing arsenic from groundwater; these processes range from ion exchange and activated alumina to reverse osmosis, coagulation and filtration. Each of these technologies have their own pros and cons, but in cases where arsenic treatment is the main treatment objective, adsorption is the ideal technology from a cost and ease of operation standpoint.
What is adsorption?
Adsorption is a continuous process conducted at a specific flow rate or velocity downward through a fixed bed adsorber. The adsorber is filled with a special media that attracts the target contaminant via active sites on exposed surfaces of the media. These medias are typically highly porous to increase the amount of active sites that are available for adsorption. For arsenic removal, iron oxide has been shown to be a highly selective adsorbent that is mechanically robust and economical to implement.
What makes adsorption the ideal technology?
Adsorption is a simple, passive process with a relatively low cost compared to other
technologies. The media is used until it can no longer sufficiently remove arsenic, a point called the breakthrough point. One of the advantages of iron adsorption is the predictability of the breakthrough which allows ample time to schedule a replacement of media. Comparatively, infrequent monitoring can give optimum performance, and both arsenate and arsenite are removed.
De Nora SORB 33® arsenic adsorption system
The De Nora SORB 33® arsenic removal system is a fixed-bed adsorption system that uses a granular ferric oxide media for the adsorption of dissolved arsenic. The system employs a simple “pump and treat” process that flows pressurized well or spring water through a fixed-bed pressure vessel containing the media where the arsenic removal occurs. Both arsenite (arsenic III) and arsenate (arsenic V) oxyanions are removed from water via a combination of oxidation, adsorption, occlusion (adhesion), or solid-solution formation by reaction with ferric oxide ions. Once exhausted, the media can be disposed of as non-hazardous waste and De Nora offers aftermarket support for disposal and media replacement.
Source: DNWT – De Nora Weighs Up Arsenic Removal, 4/2018
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