SOURCE - Spring 2025

Innovation Focus:Chromium 6 TechnologiesBuilding a BetterChromiumMouse TrapRoll-Up Regeneration for HexavalentChromium Ion Exchange TreatmentBy Phil ChandlerTeamwork and creativity havegenerated a new approachto provide compliance,simplicity, and cost-reduction forthe new chromium 6 (Cr6) drinkingwater standard in California. Asof October 1, 2024, the maximumcontaminant level for hexavalentchromium has been set at 10 partsper billion.Thinking outside the box, the folksat Phibro-Tech have worked withDatumpin, Chart, and Ecolab toreduce the footprint, maximizethroughput, and minimize brineand waste handling for utilitiesseeking a cost-effective solution.Ion exchange (IX) treatmentpromises to be a leading solutionfor compliance with California’snew drinking water regulationfor hexavalent chromium (Cr6).Now, innovations on a proven IXprocess called strong base anionexchange (SBA) lead the way tomake regenerating IX resin simplerfor operators, reduce liability fromstorage of hazardous materials,and provide new options for watersystems that can take advantage ofthis treatment technology.Innovative Cr6 ProcessImprovementsSBA treatment for Cr6 has beensuccessfully implemented atsites across California. A few earlyadopters, including Cal Water,installed SBA treatment with onsiteregeneration for compliance withthe first maximum contaminantlevel (MCL) in 2014 and maintainedproduction and treatment.These sites were configured witha hazardous waste storage tankfor the spent brine, due to thehigh levels of Cr6. To haul anddispose of the brine, Cal Watercontracted Phibro-Tech, a recyclerof hazardous waste materials witha permitted “Transfer, Storage,and Disposal Facility” in SouthernCalifornia. The service and regencycles with waste haul-off hasfunctioned effectively for nearly adecade. When the previous MCLwas disqualified in court in 2017,innovation and adoption of newsystems stopped.In 2023 it became apparent theMCL would be reinstated at a levelthat would leave a significantnumber of wells needing treatmentto remain in compliance. Withno ready business partner forthe next wave of Cr6 regulation,Phibro-Tech’s Plant ManagerDavid Clark needed to developa new approach. Clark revived arelationship with Phil Chandler,a principal developer of the firstgenerationSBA treatment, whohad formed his own consultingpractice as Datumpin, and togetherthey began to work out details for anew process.The first-generation small columnSBA systems were highly effectiveat removing Cr6. The innovativeregeneration processes minimizedwaste generation. Highly trainedpersonnel were needed to operatean onsite briner, regenerationcontrol station, and maintain ahazardous waste storage tankthat requires additional regulatoryapprovals and daily inspections.The early adopter customersappreciated the reliability of theSBA process but wanted a simplerregeneration process without extraonsite equipment.Clark’s answer was to capitalizeon Phibro-Tech’s capabilities as asupplier of drinking water certifiedferric chloride, as well as a haulerand processor of hazardous wastes.He realized the same tanker truckcould be used to supply a premixedsalt solution, pump the brineinto the ion exchange vessel toregenerate the resin, and completethe process by hauling away theused brine containing Cr6.With this innovative concept,“Roll-Up Regeneration” wasborn. The regeneration only takesa few hours, minimizing downtimefor the treatment process. Anonsite briner, regenerationstation, and hazardous wastestorage tank are not required,leaving only the SBA columns andprefilters onsite. With a lead-lagconfiguration of two IX vessels inseries, regeneration of the leadvessel may be completed while thesecond vessel continues solo.Chemical composition of thesource water plays a major partin determining the specificconfiguration of an appropriateSBA treatment train. Theoperations plan tailors thetreatment configuration andregeneration sequence to thespecific water chemistry of thesite. Phibro-Tech techniciansare certified Grade 2 treatmentoperators, and work in conjunction16 SOURCE | SPRING 2025 | www.ca-nv-awwa.org

Phibro-tech photo courtesy of Phibro-Teck. Tank p hoto courtesy of Phil Chandler.with the water system’s treatmentoperators to oversee theregeneration process.The Path AheadAlthough Phibro-Tech set outto simply provide the Roll-UpRegeneration component, thecompany has teamed up withother companies that together canoffer a complete Cr6 solution. Inaddition to Datumpin, the groupincludes the global equipmentmanufacturer Chart Water, andEcolab providing Purolite Resins.Several drinking water providersare conducting pilot studies tooptimize their SBA treatment usingRoll-Up Regeneration. Phibro-Tech’s Regional Sales ManagerJeremy Rosenfeld states thatseveral other water systems arelearning more about the benefitsof their innovation on this proventreatment approach.“The things they like best are howeasy it is for the operators, theefficient regeneration process,and not needing to use dangerouschemicals in the treatment processor store a hazardous substance onsite,”said Jeremy.Jeremy noted the capitalcost is lower than most othertreatment solutions, and byoptimizing Roll-Up Regenerationthe operating cost is also verycompetitive.About the author:Phil Chandler isan environmentalSystems Engineerwith 30 years ofexperience inwater, gas and oilapplications. Philhas led complex environmentalresearch and equipmentengineering programs in theUK, USA, Europe and Japan. Philcurrently serves as President ofdatumpin inc which provides assethealth data services for a range ofequipment applications.With 8-foot ion exchange vessels behind it, a Phibro-Techtanker prepares to offload brine in Rosemead, CA.Ion Exchange 101Ion exchange (IX) resin treatment is a “best available technology”(BAT) for hexavalent chromium. The choices include “strongbase” or “weak base” anion exchange resin, abbreviated as SBAor WBA. The resin choice is driven by water chemistry.Weak Base (WBA): Operations with high total dissolved solids(TDS) may want to consider WBA.With WBA IX treatment, the influent water pH must first belowered by adding acid or CO2 so that the resin is in the rightform for chromate uptake. Subsequently, the pH must bereadjusted after the IX treatment to the same level as the influentto prevent corrosion potential before going to distribution. WBAIX treatment has been operational at a Superfund site in Glendale,California following a landmark research project that ran from2001-2015. WBA IX beds can treat for years before a change out isrequired. A drawback for WBA is that the resin also attracts andbuilds up uranium over time which can trigger special disposalrequirements for radioactive waste.Strong Base (SBA): the advantage is it operates at neutral pHand can be regenerated with a low-cost salt brine. The length ofthe service cycle is dictated by the other TDS in the water. Whenthe IX hits a predetermined Cr6 effluent level, a regen is initiatedwhere the chlorides in the regenerant replace the Cr6 on theresin bead.First-generation SBA chromium (VI) treatment vessels and a brine tank were allhoused in containers, with elaborate controls and a separate waste brine tank.Spent brine is captured and hauled away for further processing.Because the frequency of regeneration, generally, relatively lowlevels of other anions, including uranium, do not require specialhandling. Any brine stored on-site after regeneration is classifiedas hazardous waste due to the Cr6levels.‒ By Cathy Swanson, Director of Business Development forEmerging Markets for EcoLab Purolite Resinswww.ca-nv-awwa.org | SPRING 2025 17