Wastewater Ion Exchange (WWIX) Frequently Asked Questions (FAQs)

Wastewater Ion Exchange (WWIX) is a service exchange-based technology using portable tanks of ion exchange (IX) resin or adsorptive media to remove contaminants from wastewater.

Xylem’s nationwide service network delivers fresh WWIX tanks to a customer’s facility for use in removing specific targeted contaminants. Once exhausted, the WWIX tanks are removed and replaced with fresh tanks. The exhausted tanks are returned to Evoqua’s RCRA-permitted processing facility where the media is removed, and the tank is refilled for the next use. The spent media is regenerated or recovered while the contaminants themselves are typically recovered off-site.

Any dissolved, ionic (charged) contaminant can potentially be removed with WWIX technology. Regulated heavy metals, such as arsenic, cadmium, chromium, copper, lead, mercury, nickel, zinc, etc., are well-removed by WWIX technology as are other regulated contaminants such as cyanide, perchlorate, etc. Similarly, the technology can easily remove typically non-regulated ions such as calcium, potassium, sodium, chloride, nitrate, sulfate, etc. to facilitate recovery of the water for reuse.

Dilute, metal-bearing (both regulated and non-regulated metals) wastewaters are typically excellent candidates for WWIX treatment. Wastewaters can be treated either to meet discharge regulations for wastewater discharge, or for reuse in the generating process or other compatible processes in the facility.

WWIX treatment may not be technically or economically feasible for wastewaters with higher concentrations of contaminants. In these cases, Evoqua can supply conventional precipitation treatment equipment for discharge compliance scenarios or reverse osmosis (RO) for water recovery and reuse scenarios. There may also be an opportunity to combine conventional and/or membrane and WWIX technologies to achieve the optimal solution.

Spent IX resins and adsorptive media are considered wastewater treatment residuals. Some may be classified as hazardous waste, if they meet the EPA’s definition of a listed (based on generating process) or characteristic (based on certain traits of the spent media itself) hazardous waste, while others may be classified as non-hazardous wastes.

WWIX media used to treat wastewaters from electroplating, chemical etching, milling and coating operations, as well as a number of related finishing processes such as cleaning or anodizing, may result in spent WWIX media being classified as a “listed” hazardous waste; specifically with hazardous waste codes of F006 or F019.

If a spent WWIX media exhibits, based on analysis, characteristics such as ignitability, corrosivity, reactivity or toxicity (as defined in EPA regulations), the spent WWIX media is considered a “characteristic” hazardous waste. The most common types of characteristic hazardous wastes generated from metal-bearing WWIX treatment are D003 (containing reactive cyanide) and D004-D011 (containing specific metals above an explicit level).

Operating WWIX media tanks are monitored in a number of different ways to determine when they are spent. In discharge compliance applications, the specific contaminant(s) are measured before and after the WWIX tanks, and the tanks are switched out when the effluent contaminant concentration meets or exceeds an action level appropriate for the application. In water recovery and reuse applications, the effluent water quality is measured for total dissolved solids (TDS, typically measured via conductivity) or resistivity and tanks are switched out based on the water quality requirement specific to the application.  Carbon tanks are monitored more qualitatively, compared to tanks for metals-removal, as the carbon mainly serves to protect the metals/TDS-removal media from fouling; typically carbon tanks are changed after a specific time interval as opposed to influent/effluent measurements.

Each application is evaluated by reviewing the type of generating process, process conditions (flow rate, daily wastewater volume generated), the desired outcome (discharge compliance or water recovery and reuse) and the contaminants involved; preferably, an initial analysis of a representative wastewater sample is completed. That information is used to determine the most appropriate media for the application and to also estimate the throughput and ultimately the number of WWIX tanks that will be consumed annually.

The majority of spent IX resins and adsorptive media received by the Xylem processing facility in Roseville, MN, are either regenerated or sent offsite for recovery. If the IX resins are regenerated, then the regeneration residuals (heavy metal-containing solids) are sent offsite for thermal recovery. Some media, depending on their type or contaminants, may be sent offsite for other disposal options.