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For years,the Tampa Bay region reliedon groundwater to meet its drinkingwater needs. However, in the early 1990s,the region was required by contractualmandate to reduce groundwater pump-ing at 11 long-producing wellfields inorder to help the surrounding environ-ment rest and recover. New non-ground-water sources were needed.

After years of studying water supplyoptions, the Utility developed a $610 mil-lion Master Water Plan blueprint to meet

the long-term drinking water needs formore than two million customers in theTampa Bay region. In 1998, the first con-figuration of projects was approved. Akey component of the Master WaterPlan’s first phase was a strategy to deliversurface water. Therefore, a surface watertreatment plant (SWTP) was proposed.

In March 2000, the Utility entered intoa $144 million,15-year design/build/oper-ate (DBO) agreement with a team led byUSFilter Operating Services, Houston, to

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Advanced Surface Water Treatment Plant’s

Enhanced Coagulation Treatment ProcessRequires Tough Protective Coatings

B y the late 1990s, Florida’s largest wholesale watersupplier, Tampa Bay Water (the Utility), was fac-ing a quandary all too familiar to managers of thenation’s drinking water infrastructure. The contract

creating Tampa Bay Water required that the utility replace 68 million gallons per day (mgd) of groundwater with new, alternative sources. Water usage in the tri-county region(Hillsborough, Pasco and Pinellas counties and the cities ofTampa, St. Petersburg and New Port Richey) had soared from177.7 mgd in 1980 to 218.5 mgd in 1995. By 1998 that numberhad jumped to 232.36 mgd, and was projected to continue risingas the region grew. The Utility had to develop new sources toreplace the groundwater lost to permit reductions and to meetthe region’s continuing growth.

By Lake H. Barrett, Jr.

COATINGS

carry out the design and construction ofthe new state-of-the-art surface watertreatment plant and to provide for its day-to-day operation. Owned by regional util-ity Tampa Bay Water, the plant is amongthe most technologically sophisticated inthe world.

The Utility’s first surface water plantalso is the nation’s largest DBO waterproject. The new 66-mgd regional treat-ment plant began operation inSeptember 2002.Located on 435 acres inHillsborough County, the SWTP operates24 hours a day,seven days a week.TampaBay Water officials estimate that this pub-lic/private partnership over the 15-yearterm of the contract will save the regionan estimated $80 million.

Role of High-PerformanceCoatings in Plant Design

USFilter turned to the global, full-serv-ice consulting, engineering and con-struction firm of CDM, Tampa, Fla., as its

design partner. Because of the accelerat-ed schedule for the project, the CDMdesign team was required to producecomplete water treatment plant designdrawings for submittal to permittingagencies in less than six months.

From the notice to proceed,the SWTPwas up and running in about 28 months,including design, permitting and con-struction, according to Project Managerand CDM Vice President Richard D.Moore, P.E.

“That’s about half of the time to imple-ment a conventional design/build/oper-ate project of this magnitude,”Moore said.

CDM design engineers faced the for-midable challenge of protecting diverseplant operation surfaces and substratesspread over 20 acres, including carbonsteel, concrete (both pre-cast andpoured-in-place), concrete masonryunits (CMU), ductile iron and alloy steel.

During construction, CDM designengineers turned to Tnemec Company,

Inc., Kansas City, Mo., for answers to thischallenge. Because of the sophisticatedwater treatment technologies designedfor the plant, Moore noted that thedesign team looked for the most reliablehigh-performance coatings systems forthe 50,000 square feet of the plant’s mul-tiple surfaces.

Technological SophisticationPlans called for the use of the high

rate ballasted Actiflo flocculationprocess. This process is particularlyadvantageous when treating large flowrates with variable raw water quality—the conditions anticipated for theregional water treatment plant.The facil-ity treats water from the Hillsboroughand Alafia rivers as well as the TampaBypass Canal to standards that exceedthe current EPA Safe Drinking Water Actrequirements for potable water.

It is the largest Actiflo plant for munic-ipal water in the United States.The plant

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Tampa Bay Water’s Surface Water Treatment Plant

A: Protective linings act as secondary containmentfor the submerged concrete.B: Protective liningsact as secondary containment for the concreteflooring,and color-coordinated coatings protect theexposed steel piping.C: Corrosion-resistantcoatings cover the structural steel canopy.

A

B

C

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also utilizes ozone as the primary disin-fectant and granular activated carbon asa medium for the biological filtration,providing advanced treatment.

The process uses sulfuric acid tolower the pH of the raw water and ferricsulfate to coagulate the water. Fine grainsand and polymer are added to thewater in the injection tank (See diagramat left).

The water then moves into the matu-ration tank for further mixing that allowsthe sand and flocculant particles (floc)to join together before passing into thesettling tank. In the settling tank, the flocand raw water are completely separated.The sand’s weight forces the floc to fall tothe bottom,allowing the treated water torise to the top for further treatment.Lamella tube settlers are used toimprove the separation.At this point, thepH level of the water is lower than nor-mal. Lime is added to help adjust thewater’s pH level back to normal and pre-pare the water for disinfection.

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Floor coatings and overlayments protect the concrete flooring seen here in the pilot plant,located in the operationsbuilding. The pilot plant is a miniature of the entire plant operation;every process can be tested here for performance.

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Ozone gas then is added as the pri-mary disinfectant. It destroys themicroorganisms including bacteria,viruses and protozoa that may be left inthe water. Ozone also oxidizes anyremaining organic particles that may beleft in the water.

After disinfecting the water, the pH israised again with lime to prepare it forthe filtration process. The water movesfrom the ozone tank to the biologicallyactive filtration area. During the biologi-cally active filtration process,“good bac-teria”oxidize the remaining organic mol-ecules. Layers of sand and granular acti-vated carbon then filter out any remain-ing particles.

After the biologically active filtrationprocess, the water moves to a storagearea (or clearwell) for a second disinfec-tion process. Chloramine is added tomaintain the residual chlorine in the dis-tribution process and to ensure that thewater supply remains free of bacteria.

After leaving the surface water plant,the water moves to a blending facilitywhere it is merged with treated waterfrom the nearby groundwater plant.Then,the combined water is piped to TampaBay Water’s member governments.

Tampa Bay Surface Water Treatment Plant Facts• The plant treats 66 million gallons of water a day, enough to fill 94 Olympic-size pools or 1.06 billion cups of water.

• The weight of the water produced in one day at the plant is equal to the 54 million pound concrete base of the Statue of Liberty.

• Approximately 15,000 cubic yards of concrete were used to build the plant, equivalent to a 46-mile sidewalk.

U.S. Drinking Water Infrastructure Needs• A recent American Water Works Association (AWWA) study on the nation’s drinking water infrastructure found that the nation

must invest an additional $250 billion to replace aging drinking water infrastructure over the next 30 years.

• The AWWA report finds that spending on pipe replacement must triple over the next 30 years in order for the nation to main-tain a high quality drinking water infrastructure.

• The American drinking water infrastructure network spans 700,000 miles, more than four times longer than the NationalHighway System.

• A recent study by Water Infrastructure Network (WIN), a coalition of industry, engineering, professional and environmentalgroups,predicts that total expenditures for drinking water and wastewater infrastructure over the next twenty years may rangefrom $492 billion to $820 billion.

• The EPA’s Clean Water and Drinking Water Infrastructure Gap Analysis report released last year, under a "no revenue growth"scenario, estimates a total capital payments gap of $122 billion for clean water and $102 billion for drinking water over thenext 20 years.

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The plant is fully automated. At thecontrol station, changes in water qualityand any changes in the process are mon-itored continuously. If a problem occurs,an alarm will sound,identifying the prob-lem area. The automated controls allowthe operators to react quickly and makeany necessary changes.

Coating Solutions Tnemec consultants specified four cat-

egories of coatings systems needed to pro-tect the wide variety of substrates through-out the treatment plant, including protec-tive linings, exterior masonry and steelcoatings, corrosion resistant coatings andfloor coatings and overlayment systems.

Protective linings included novolacepoxies, vinyl esters, amine epoxies, elas-tomeric aromatic urethanes and modi-fied aliphatic amine epoxy mortars.Thesecoatings were specified for the interior ofthe settling, maturation, coagulation andinjection tanks, and on submerged con-crete in the gravity thickener tank,recyclesurge basin and influent box. They wereselected to resist corrosive industrial andmunicipal wastewater and hydrogen sul-fide gas permeation as well as abrasion,cavitation and chemical exposure.

Exterior masonry and steel coatingsincluded zinc-rich primers, epoxies,aliphatic urethanes, acrylics, water-basedacrylics, saline water repellants, sealersand stains. These were specified for allpiping and pumps, exterior concrete,CMU, containment areas and in themaintenance and storage buildings.These coatings and water repellantswere chosen because of their ability toresist atmospheric corrosion in a coastalenvironment and to improve the long-term aesthetics of the facility.

Corrosion resistant coatings includedpolyamines, amido-amines and cyclo-aliphatic epoxies as well as fiber-rein-forced polymers.These were specified forall interior and exterior pipe galleries, fil-ters, submerged steel, walls and ceilingsof the operations building. These corro-sion-resistant coatings were required toprotect against the numerous processingchemicals used in this facility.

Floor coatings and overlaymentsincluded resinous floor epoxies applied to

the maintenance area, chemical storagearea, gravity thickener room, controlrooms and bathrooms.These coatings andoverlayments were selected to decreasemaintenance costs, provide slip-resistantsurfaces,increase cleanability and providea pleasing work environment.

Throughout the plant, wherever therewere piping and valves, a tough

polyurethane overcoat for UV protectionwas specified. Because of the many col-ors available, Tampa Bay Water was ableto coat the piping infrastructure withseven colors,one for each process in thetreatment cycle.

“Because of the plant’s enhancedcoagulation treatment process, it wasextremely important to have the right

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coatings to protect the plant’s exten-sive concrete and steel substratesagainst this low pH water environ-ment, which is aggressive and border-line corrosive,” USFilter Plant ManagerDavid Hackworth said.

Therefore,a great diversity of coatingswas needed. Besides chemical and cor-rosion resistance, the coatings needed toadhere to both the steel and concretesubstrates immersed in potable water.

“The integrity and excellence of coat-ing systems is critical to the efficient oper-ation of this state-of-the-art, sophisticatedfacility,” Hackworth said. “It’s one morething we don’t have to worry about.”

About the Author:Lake H. Barrett, Jr., is the director of water andwastewater operations at Tnemec in Kansas City, Mo.He holds a Bachelor’s degree from Penn StateUniversity and is pursuing a Master’s degree inmanagement. He is an active member of SSAC,NACE, ASME, AWWA and WEF.

F

Color-coordinated,exterior steel coatings were used to protect and label the exposed piping seen here in the pipe gallery.

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Adrienne Miller at 847-391-1036;amiller@sgcmail.com.