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<br />MWSI Project <br />Phase II Effluent Management Summary Report - DRAFT <br /> <br />Water to make evaporation releases from its onstream South Platte reservoirs. As a <br />practical result, Denver Water currently may not make reuse of waters diverted from its <br />Moffat system. <br /> <br />August 22, 1995 <br /> <br />Colorado - Big Thompson Project: The 1938 repayment contract for the <br />Colorado-Big Thompson Project dedicates the reuse of water diverted from the Colorado <br />River Basin to the South Platte River Basin under the CBT Project to the water users in <br />the Northern Colorado Water Conservancy District as the water may appear from time to <br />time at their headgates. This was done to provide a benefit (in the form of increased <br />return flows) to those lands located in the lower portion of the Northern Colorado Water <br />Conservancy District. This water is not available to be dedicated to any other purpose. <br /> <br />Economics and Public Perception of Potable Direcl Use <br /> <br />Direct potable reuse involves the treatment of reusable wastewater effluent to <br />attain water quality levels that are suitable for potable water uses and has been the subject <br />of several previous studies. Denver Water and the U.S. Environmental Protection <br />Agency developed and operated a pilot potable reuse plant during the 1980's but <br />discontinued the project due to high costs and operational problems. The City of Aurora <br />has also considered potable water reuse as a future source of water supply. Potable reuse <br />was evaluated and eliminated from detailed consideration in the Metropolitan Denver <br />Water Supply EIS primarily due to high costs in comparison to other available sources of <br />supply and concerns about reliability. (U.S. Army Corps of Engineers 1988). <br /> <br />However, the technology of potable reuse has been demonstrated to be reliable on <br />a full scale basis and is being used in other cities throughout the country to produce <br />drinking water. Potable reuse has been incorporated into the water supply system of <br />Fairfax County, Virginia for over twenty years, and the San Diego County Water <br />Authority is planning to augment its water supply by over 20,000 acre-feet per year by <br />the year 2000 with repurified effluent for potable supply. <br /> <br />The two major obstacles to potable reuse have been high costs and concerns about <br />public health and safety. San Diego estimates the total annual cost for its water <br />repurification project at $900 to $1,000 per acre-foot of repurified water produced. This <br />includes conventional tertiary treatment of approximately 20 million gallons per day of <br />wastewater effluent followed by advanced disinfection, reverse osmosis, and ion <br />exchange technology, continuous monitoring, and pumping to a raw water supply <br />reservoir for blending purposes. This translates to a capital cost of over $13,000 per acre- <br />foot. While these costs have previously been perceived as prohibitive, potable reuse may <br />be rapidly becoming economically viable as the costs for development of alternative <br />surface water supply sources increase to these levels. One mitigating factor in the <br />economics of potable reuse is that there probably would not by any raw water costs <br />associated with potable reuse as the metro area generates a surplus of reusable effluent, as <br />discussed in subsequent sections of this document. <br /> <br />17 <br />