Full Description

The Peace River/Manasota Regional Water Supply Authority (Authority) of Sarasota, Florida was formed to provide regionalwater supply to a four County area of southwestern Florida. The Authority is expanding the Peace RiverRegional Water Supply Facility to meet water supply contracts to deliver 18 million gallons per day(mgd). The facility relies on surface water from the Peace River, a highly variable water source withflows that range from billions of gallons per day to periods of almost no flow. The expanded watersupply facility includes a river pumping station with a capacity of 36 mgd, a surface reservoir with acapacity of 525 million gallons (mg), a water treatment plant with a capacity of 24 mgd, and an aquiferstorage and recovery (ASR) system consisting of 21 wells with a combined design storage capacity ofabout 5,500 mg.The ASR system relies on wells to store finished water at times when raw water can be diverted andtreated at rates in excess of the daily demand. Water is recovered from these same wells to meet demandduring periods of low river flow when diversion is prohibited. The "bulk recovery efficiency" of theASR system is a measure of the volume of water that can be recovered from storage. The complex flowpatterns of the Suwannee aquifer, the target storage interval at the Peace River Facility, result in recoveryefficiencies that can vary from 10 percent to over 90 percent. The quality of water recovered from theASR system degrades during recovery due to mixing with native groundwater, complicating theoperation of this system.Innovative approaches involving well design, wellfield configuration, and pretreatment are beingimplemented to improve recovery efficiency and water quality of the ASR system. These approacheswere developed following a careful analysis of the fundamental physical concepts controlling successfulapplication of ASR technology in this environment. Significant changes in the design process include:shortening of the well completion interval where possible; targeting of storage zones which provide amore uniform distribution of aquifer permeability where possible; favoring of a close, symmetricalspacing of wells within the wellfield; and, favoring a symmetrical pattern of recharge and recovery.These design innovations are planned to be combined with a computer-based Decision Support Tool(DST) to assist in the operation of the Facility. Frequent operator decisions are required in order tobalance the demand for water, daily flow and quality of water in the Peace River, volume and quality ofwater in storage in the raw water reservoir, and volume and quality of water in storage in the ASRsystem. The operator's decisions are complicated because of the unique performance and recoverycharacteristics of the ASR wells. Also, in periods of low flow in the Peace River, it becomes necessaryto blend water from multiple sources (river, raw water reservoir, each of 21 ASR wells). The DST willprovide the plant operator with real-time information on flow and water quality conditions for each ofthe ASR wells, allowing the operator to manage the quality of water produced and extend the recoveryfrom the wells beyond the 500 mg/L total dissolved solids recovery threshold. The DST will also continuously update aforecast of the facility's reserves to sustain demand during periods of low or no river flow. This lastfeature of the DST is critical during droughts, when the Authority must rely on water stored in the ASRsystem and the raw water reservoir as the sole source of water.The combination of innovative ASR wellfield designs and implementation of a decision support toolduring facility operations provide the means to efficiently manage the quality of water produced at thePeace River Regional Water Supply Facility. Includes figures.

Product Details

Edition: Vol. - No. Published: 06/01/2001 Number of Pages: 9File Size: 1 file , 270 KB