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At present, drinking water utilities have been reluctant to undertake reverse osmosis (RO) or nanofiltration <br />(NF) membrane projects due to the uncertainty surrounding the availability of feasible disposal options for <br />the concentrate. Zero liquid discharge (ZLD) is a sustainable disposal option that represents a long-term <br />solution to concentrate disposal for utilities that need membrane treatment to produce safe drinking water. <br />The primary barrier to implementing ZLD is the lack of cost and performance data developed for drinking <br />water systems under conditions unique to Colorado. Pilot tests demonstrating ZLD will help resolve the <br />technical and financial uncertainties which currently hinder its implementation making additional water <br />supplies available for municipal use. <br />Objectives of the proposed pilot testing will include <br />• Comparing the performance of alternative ZLD technologies; <br />• Developing capital, operating and maintenance costs for ZLD technologies; <br />• Completing a detailed analysis of energy consumption; <br />• Determining the quantity and quality of the water recovered from the ZLD process; <br />• Characterizing the quantity and composition of solid created by the process; <br />• Determining the handling, transportation and disposal requirements for solids created by the <br />process; <br />• Identifying potential marketable residuals from the ZLD process and summarizing applicable <br />case studies; <br />• Assessing the different requirements of two distinct source waters representing different water <br />quality conditions for the State of Colorado. <br />Pilot testing -,vill occur at two sites with two different water qualities for Colorado. The first site at the Citv of <br />Brighton's RO Water Treatment Plant (WTP) will represent water quality indicative of the South Platte River basin. <br />The second site, located at the City of La Junta's RO WTP, characterizes typical Arkansas River basin water. These <br />plants have distinct water quality challenges. In the case of Brighton, the concentrate disposal challenge is caused b-,- <br />nitrate, whereas, in the case of La Junta, the challenge is caused by selenium. Brighton is a rapidly growing <br />community, in which increased municipal and industrial (M&I) demand is an immediate issue. La Junta is <br />representative of a small agricultural community with limited financial resources that must confront a highly technical <br />and costly disposal issue. These communities are representative of the statewide concentrate disposal issues facing <br />utilities statewide. <br />The pilot testing consists of 9 tasks: <br />1. Literature Search <br />2. Experimental Plan <br />3. Design Layouts <br />4. Install Equipment <br />5. Pilot Operations <br />6. Water Sampling <br />7. Support Energy Study <br />8. Final Report <br />9. Project Management & QC <br />Deliverables include various technical memorandum, experimental plan, design drawings, pilot plant <br />equipment, capital and operating costs under multiple conditions, analysis of water samples, analysis of <br />solids sampling, process schematics and water and energy balances, and a final report. Estimated time frame <br />for the project is January 2009 through January 2010. <br />Threshohl and Evallratiosi Criteria <br />The application articulates how the project meets all four Threshold Criteria. <br />2