Recycled Filter Carbon
Residential water filters and reverse osmosis units normally use filter carbon in some form, and the carbon used in residential units is normally new carbon. There is no program that we know of that recycles filter carbon from small household filter cartridges for reuse as filter carbon. Over the years some vendors have advertised recycling of spent filter cartridges, but these programs were, in our view, more about marketing than recycling, designed to appeal to environmentally conscious customers and to promote cartridge replacement sales. Recycling of small cartridge carbon is simply not economically feasible.
However, carbon recycling does happen, and in a big way, with large industrial and municipal filter applications.
Here’s an interesting account of how carbon recycling works, from the Calgon Corporation, a major provider of filter carbon.
What should treatment operators know about the differences between virgin and reactivated GAC when evaluating options for PFC removal?
Although virgin and reactivated GAC may be of the same starting material and same activity level, they are two distinct products. Virgin GAC is an activated carbon product that has not been used in a previous application, so its quality and performance are consistent. Reactivated GAC is a product whose capacity was exhausted (spent) in a previous application and has undergone a high-temperature thermal process to destroy adsorbed material (remove contaminants) and restore a majority of the adsorptive capacity that allows the product to be reused in appropriate applications. The reactivation process alters the pore structure and can impact performance/quality, but can still provide a cost-effective treatment solution.
Within the term “reactivated GAC” it is also important to distinguish between a custom-reactivated GAC and a pool reactivated GAC. A custom-reactivated GAC is a product that has been previously used and spent in a specific customer’s application, removed from service, segregated from other spent GAC, reactivated, and returned to the same customer for reuse. In a pool reactivated product, spent carbons from a variety of customers’ applications are co-mingled, reactivated, and used for a variety of non-potable applications. The quality of a custom-reactivated product is generally higher than the quality of a pool-reactivated product, but is highly dependent on the application in which it was used, the reactivation conditions, and the initial carbon product. Custom reactivation is most economical for quantities above 20,000 pounds. It is vital to select a virgin material that can withstand multiple cycles of treatment and reactivation. A reagglomerated, bituminous, coal-based product has been shown to be a superior base product for reactivated GAC.