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To help meet the future water needs of eastern Central Florida, a treatability study is being conducted by the St. JohnsRiver Water Management District and CH2M HILL to quantify the treatment requirements andcosts for a potential surface water treatment facility to be located along the reach of the St. JohnsRiver between the southern end of Lake Monroe in Sanford and De Land. This pilot study willidentify the feasibility, appropriate use, treatment technologies and costs to use surface water tooffset groundwater demands. The St. Johns River water has typical surface water characteristics for Florida. The characteristicdark brown color of the water is due to the organics in the water. These organics are mostlydissolved humic and fulvic matter. Total organic carbon concentrations are often in excess of 30mg/L with colors exceeding 400 Pt-Co. Additionally, the St. Johns River has uniquecharacteristics due to the brackish content of the water. This brackish surface water has totaldissolved solids (TDS) concentrations ranging from 400 milligrams per liter (mg/L) to 1,060mg/L and chloride concentrations ranging from 139 mg/L to 455 mg/L. Because of these uniquecharacteristics, partial desalting must be used along with conventional treatment.Selecting treatment technologies for any water treatment system is driven primarily by drinkingwater regulations and the meeting of consumer expectations. For surface water treatment, theprimary regulations are the Enhanced Surface Water Treatment Rules (ESWTR) and theDisinfectant/Disinfectant Byproduct (D/DBP) Rules. The planning process for any treatmentfacility on the St. Johns River has a 5- to 10-year window. Therefore, upon construction of thisfacility, compliance would likely be required for the Long Term 2 (LT2) ESWTR and Stage 2D/DBP rules.The approach to meeting these regulations is multi-barrier treatment involving the following unitprocesses:coagulation and flocculation;clarification;filtration; and,disinfection.This approach requires each process to remove waterborne pathogens, with each processoperating at a high rate of efficiency. The effectiveness is cumulative, in that each unit processhelps the subsequent unit process work more effectively than if operated alone. The basis and goals of the pilot testing was to evaluate pretreatment of the raw water for particleand organics removal. The pretreatments were further evaluated with respect to reverse osmosismembrane performance based on the pretreated water quality.Pilot testing consisted of several different phases, each with different goals. During the firstphase, Phase 1A, pretreatment systems were evaluated based on treated water quality and reverseosmosis membrane response. The following three pretreatment systems were evaluated duringPhase 1A:the Super Pulsator (SuperP) blanket clarifier followed by dual media gravity filtration;the Actiflo micro-sand ballasted clarifier followed by dual media gravity filtration; and,the Zenon immersed ultra-filter with coagulation in tank.Based on the results of Phase 1A, all three pretreatment systems were determined to be viablepretreatments for reverse osmosis membrane systems.The goal of the second phase of testing, Phase 1B, was to compare the four different membranesand select the best performing membrane for further testing in a multi-element high recoverysystem. During Phase 1B, the SuperP/media filtration pretreatment was used for pretreatment tothe following four single element membranes:Filmtec BW30FR;TriSep X-20;Hydranautics LFC1; and,Osmonics SG.This paper summarizes the results of the Phase 1B lead element membrane selection. Includes tables, figures.

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Edition: Vol. - No. Published: 11/02/2003 Number of Pages: 8File Size: 1 file , 310 KB