Suspended Ion Exchange treatment in Tampa

Ramboll has helped The City of Tampa test a pioneering technology in the United States for treating drinking water.

Challenges: Variable water quality from the primary water source

The David L. Tippin Water Treatment Facility produces an average of 76.7 million gallons of potable water every day to serve over 717,000 residents and visitors. In recent years, this plant has experienced operational challenges caused by variable water quality from the Hillsborough River, the city’s primary water source.

Exploring a cost-effective alternative

As part of their master-planning efforts, the city wanted to explore cost-effective alternative treatment technologies that improve the long-term reliability and flexibility in meeting the city’s goals for finished water quality, regardless of high seasonal variabilities in their source water.

Ramboll, alongside Carollo, PWNT Technologies, Garney Construction, and Wharton Smith, Inc. recommended the exploration of suspended ion exchange (SIX^®), a Netherland-born, non-proprietary advanced water treatment technology that specializes in high-efficiency organics removal.

So, in collaboration with Carollo Engineers, Ramboll led a year-long pilot study of this pioneering technology at the David L. Tippin Water Treatment Facility, which was the first large-scale test of the technology in the United States.

Process

Throughout the 10-month study, the team evaluated the SIX system’s ability to remove organics and other anions from raw water and its effects on the DLWTF’s downstream operations, water quality, and process performance. Since this European system was adjusted and sized for a U.S. plant, TWT also made careful operational pivots to ensure it met the City’s standards and remained accessible to the plant staff.

SIX and coagulation were soon determined to complement each other in improving the plants’ overall treatment outcomes. SIX’s non-proprietary anionic exchange resin adsorbed bicarbonate ions to reduce raw water alkalinity, which, in turn, lowered the coagulation pH and improved organics removal.

Further downstream, the addition of SIX and the corresponding coagulation lowered the ozone dose by 27 percent and, thanks to the lower headloss accumulation, doubled unit filter run volumes (UFRVs) and allowed filter loading rates of up to 8 gem per square foot. This last result was secured by optimizing the existing filters and building new filters with an enhanced media configuration and higher allowable headloss.

Results

With these various enhancements, the pilot plant achieved the following feats:

Improved finished water quality, resulting in an average finished water TOC of 1.4 mg/L compared to the current full-scale average of 2.0 mg/L.
Enhanced water taste, smell, and color.
Reduced demand for coagulant and other chemicals (e.g., polymer, caustic acid, lime) and the complete removal of pH-depressing acids from the treatment train, translating to chemical cost savings of up to $1.6 million per year.
Solids production that is 37 percent less than the current baseline.

The Ramboll team included engineers from the Netherlands who have had lead roles in earlier implementations of SIX in Europe, as well as experienced engineers from the Ramboll US business.

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