OCR Text |
Show Alternatives If total containment systems are prohibited as a wastewater treatment process, alternative processes such as oxidation ditches, activated sludge systems, trickling filter systems, ( the three processes are termed mechanical systems) or lagoon discharge systems will be necessary to dispose of wastewater. These processes are much more expensive and require a substantial investment in capital and personnel with the expertise to operate these types of systems. The technical expertise required is of major concern to many small communities in Utah. Further, higher levels of treatment may be necessary if the wastewater effluent is discharged to surface waters. Capital construction cost comparisons of systems built in Utah show that total containment systems generally cost slightly less than mechanical or discharging lagoon systems. Operation and maintenance costs are a major factor in mechanical and discharging lagoon systems when total costs are considered. The communities that have selected total containment systems in Utah have based their choice partly on the lower construction and operation costs, as well as ease of operation. The Division of Water Quality encourages the selection of the least costly treatment alternative which will still allow a community to meet pertinent water quality standards in order to stretch water pollution control dollars to best serve the citizens of Utah with improved water quality. Cost Effectiveness Capital construction costs to replace the existing total containment systems with mechanical treatment systems in Utah is estimated to range from $ 125 million to $ 137 million based on average cost per mgd of the Aurora, Centerfield, Santaquin and Ash Creek systems in Utah. Amortizing the capital construction figure over 30 years at 5.64 percent ( state discount rate) with the 86 estimated annual savings of 3,300 acre- feet gives a cost of $ 2,500 to $ 2,700 per acre- foot. With O & M costs estimated at $ 200 per acre- foot, total annual cost is $ 2,700 to $ 2,900 per acre- foot of water conserved by eliminating evaporation as a means of wastewater treatment. As population growth occurs and under the pressure of increasing water quality awareness, new wastewater treatment plants will be built in Utah. The increased incremental construction cost of alternatives to evaporation as a principal means of treatment is estimated at $ 440,000 per mgd of capacity based on the average for alternatives for the Aurora, Centerfield, Santaquin and Ash Creek systems in Utah. Coupling this incremental construction cost amortized over 30 years at 5.64 percent with a savings of 450 acre- feet per mgd results in a incremental capital cost of approximately $ 170 per acre- foot of water conserved. With the additional estimated O & M cost of $ 200 per acre- foot, the resulting total incremental annual cost of water conservation in new wastewater treatment plants by eliminating evaporation as a principal process is estimated at $ 370 per acre- foot . Water Quality Considerations Mechanical or discharging systems have to dispose of the effluent. Typically, disposal is into surface waters or by land application. Discharge of sewage effluent into receiving waters raises the additional problem of water quality in the receiving waters. National Pollution Discharge Elimination Permits ( NPDES) are required when discharging effluent to surface waters. The water quality testing required to monitor NPDES permits is a costly process generally borne by the treatment facility. One of the purposes of the federal Clean Water Act ( and subsequent amendments) is to minimize the discharge of pollutants into the nation's waters which total containment systems do. |