AWWA MTC57641

The San Diego County Water Authority and the City of San Diego have been promoting the development of alternative water sources to reduce San Diego County's reliance on limited imported water supplies. Desalination of various water sources including reclaimed water and brackish groundwater are important in this regard. As the cost competitiveness of membrane desalting continues to improve due to technology advancement, water desalination is becoming the preferred alternative in many arid regions. Cost data on membrane desalination using reverse osmosis (RO) membranes is scattered over a wide range of references and simple tools to evaluate present costs are unavailable. This paper presents the methodologies used in the development of this unique cost model that is based on existing and/or planned membrane desalination plants. It focuses more on the approach used for development of the model rather than a description of the spreadsheet tool. Data was collected from existing and planned treatment plants and normalized to prepare curves for capital and operating costs. The water sources have been considered for this project include: reclaimed water and brackish groundwater. The use of existing costs provides a connection to reality with regard to costs as competitive bidding has caused the market prices to be disconnected from theoretical prices in recent years. Models for similar applications use standard curves for the other treatment processes, established 30 years before but for membrane plants. The models used for membrane plant cost estimation are largely driven by user input and guestimates. This model incorporates special membrane cost curves for low pressure and high pressure membranes to normalize membrane costs from different sources to provide specific costs based on market data and not primarily driven by user input. In addition, the information gathered provides useful information with regard to the trend in historical market costs and development in productivity for membranes. This project was conducted as a part of a research program initiated by Desalination Research and Innovation Partnership, which consists of water purveyors in the Southern California region. Includes tables, figures, appendices.