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Show Elimination of evaporation as a principal method of wastewater treatment. Public Law 102- 575, Subsection 207( f)( 2)( J) Total Containment and Evaporation Systems A total containment system is one in which there is no direct discharge of effluent to receiving waters. Sewage collection systems direct the effluent to a containment lagoon where evaporation and infiltration dispose of the effluent. Containment lagoons are sized to allow for sufficient storage to meet winter conditions when evaporation and/ or infiltration and percolation disposal rates are low. A total containment system provides minimal mechanical or chemical treatment of the wastewater; however, biological changes occur naturally in the containment lagoon which result in the treatment of the wastewater. The Utah Division of Water Quality estimates that evaporation accounts for the disposal of 40 percent of the effluent in a total containment system in Utah. The rest of the effluent of a total containment system ( 60 percent) is disposed of by infiltration and percolation. Status There are 92 wastewater treatment facilities in Utah treating a total of 98 million gallons per day ( mgd), or approximately 301,000 acre- feet per year. Of these facilities, 37 are wastewater treatment systems classified as total containment systems.( This is 41 percent of wastewater treatment systems in Utah.) Total design capacity of these 37 systems is 11.45 mgd, or approximately 12,827 acre- feet per year. Current use ( 1/ 93 - 1/ 94) is 7.38 mgd, or 8,267 acre- feet per year. In terms of amount of flow, this is only 2.75 percent of current total wastewater flows in Utah. Most total containment systems are located in small towns in rural Utah. As can be seen from the small size of the systems ( 0.05 to 2.0 mgd), relatively little of the wastewater in Utah is treated by total containment systems. Many of the systems are located in remote areas where the cost of conveyance to suitable receiving waters for disposal is prohibitive. Potential Water Savings Based on estimates from the Utah Division of Water Quality, current disposal of wastewater in Utah by evaporation from total containment systems is 3,300 acre- feet per year, or about 1 percent of the total wastewater treated annually in the state. These figures are based on estimates of 40 percent evaporation and 60 percent infiltration and percolation for total containment systems. Additional wastewater treatment plants will be required in the future to meet the needs of population growth as well as increasing emphasis on water quality. Eliminating evaporation of wastewater as a treatment process in new plant construction will conserve approximately 450 acre- feet of water per year for each mgd per year of wastewater treatment. |