Tampa City Council Approves Funding For World's Largest Suspended Ion Exchange System At The David L. Tippin Water Treatment Facility

First full-scale SIX installation in the United States will be designed to treat 140 million gallons per day

The Tampa City Council has approved funding for the design of Suspended Ion Exchange (SIX) technology at the David L. Tippin Water Treatment Facility (DLTWTF), marking a historic milestone in water treatment innovation. When completed, this facility will be the largest SIX installation in the world and the first full-scale implementation in the United States, designed to treat up to a peak of 140 million gallons per day (MGD) of drinking water.

The decision follows several years of comprehensive planning, pilot testing, and independent technical review that demonstrated SIX's ability to significantly improve finished water quality while reducing operational costs. The project represents a major advancement in the City's ongoing initiative to enhance treatment performance at the DLTWTF.

“Council’s support of this investment shows a clear commitment to doing what is right for Tampa’s future,” said Tampa Water Department Director Rory Jones. “After years of testing and data driven evaluation, our team selected Suspended Ion Exchange as the right fit for our system, one that improves water quality, reduces long term costs, and builds on the legacy of the David L. Tippin Water Treatment Facility.”

The City of Tampa Water Department is delivering this initiative through a collaborative design-build partnership led by joint venture partners Garney and Wharton-Smith with Carollo Engineers as the lead designer.

"We are honored to lead the design of the world's largest SIX system," said Carollo Project Manager and Executive Vice President Vinnie Hart. "Tampa's vision to pioneer this technology and desire for improved water quality, combined with rigorous pilot testing and the collaborative efforts of the entire project team, will establish new standards that water utilities across the country and beyond can follow. This technology is truly a game changer for the high organics waters that we see in Florida."

The DLTWTF currently produces an average of 80 MGD of high-quality drinking water for over 733,000 residents and visitors. The facility has faced seasonal challenges from variable quality from the Hillsborough River, the city’s primary water source, including elevated levels of total organic carbon (TOC) with levels over 30 mg/L. High TOC levels contribute to the formation of regulated disinfection byproducts and require increased chemical treatment processes.

SIX is a suspended ion exchange process, developed by PWNT (a wholly owned subsidiary of Nijhuis Saur Industries) as an alternative/supplement to coagulation for organics removal. It is suitable for treating surface waters to remove dissolved organics through an efficient resin contacting, separation and regeneration system, with brine used up to five times, which helps reduce waste streams and salt use.

Beyond immediate water quality improvements, SIX positions Tampa to address emerging contaminant regulations, including PFAS (Per- and Polyfluoroalkyl Substances), by removing organic matter that can interfere with downstream technologies such as granular activated carbon, making PFAS removal significantly more efficient. In addition to removal of organics, some PFOS (Perfluorooctane Sulfonic Acid) removal does occur with the SIX process.

The 10-month pilot study evaluated the SIX system's ability to remove organics and other anions from raw water and its effects on downstream operations, water quality, and process performance. Testing the entire treatment train—SIX pre-treatment followed by coagulation, flocculation, sedimentation, ozone, and biofiltration—produced results that exceeded expectations. The pilot demonstrated significant water quality improvements, reduced chemical usage by up to 79 percent with projected annual savings of $1.7-1.9M, and doubled filter efficiency. These savings were all validated by an independent 3rd party review (Black & Veatch, 2025).

With funding for the design now approved, the project team will move forward with detailed design, permitting, and construction planning.

Once operational, the facility will serve as a demonstration site for SIX technology in the United States, providing valuable operational data and establishing best practices for future installations nationwide.

About Carollo Engineers
For more than 90 years, Carollo Engineers has provided a full range of innovative planning, design, and construction management services to address the water needs of municipalities, public agencies, private developers, and industrial clients. Carollo develops robust water management strategies that leverage collaboration, provide multi-benefit solutions, and achieve sustainability and resilience. Carollo has 1,900 employees located in over 60 offices across North America. To learn more about how Carollo is “Working Wonders With Water” For more information, visit www.carollo.com