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Reclaimed Water Desalination Technologies

Reclaimed Water Desalination Technologies: A Full-Scale Performance and Cost Comparison Between Electrodialysis Reversal and Microfiltration/Reverse Osmosis

Principal Investigator and Project Manager
R. Shane Trussell, Trussell Technologies, Inc.

In an effort to satisfy a growing water demand in the face of dwindling water resources, many communities throughout the United States and the world are turning to water reclamation and reuse. Recycled water is a renewable and drought-proof resource whose availability increases proportionally with increases in potable water use. Increasingly, recycled water has been identified as the most cost-effective means of increasing the water portfolio for many municipalities (Raucher, 2006). Demand for recycled water is expected to increase rapidly over the next 20 years (CDWR, 2003), driving the need to build new water reclamation plants and expand the capacity at many existing facilities.

This report documents and compares the actual lifecycle costs and process performance of the two most common membrane processes used for removing salt from recycled water: reverse osmosis (RO) membranes with microfiltration (MF) pretreatment and electrodialysis reversal (EDR) membranes. The need to reduce the salinity of recycled water is becoming more widespread as wastewaters have become more saline and recycled water consumers have started demanding a higher quality product. In particular, recycled water users are increasingly consulting horticulturists, agriculturists, and landscaping experts to understand the impact the recycled water salt content has on specific irrigation applications. As a result, it has become more commonplace for recycled water consumers to require lower salinity in their recycled water. Reduced salinity is also of interest to other recycled water applications such as industrial applications and environmental restoration. Recently, the regulatory community has indicated the need to desalinate recycled water, and the California State Water Board has drafted a document (Policy for Water Quality Control for Recycled Water) that requires agencies to prepare basin-specific salt and nutrient management plans by 2014. MF/RO and EDR have both been successfully applied to desalting in water reuse, but a full comparison of the actual lifecycle costs of existing full-scale systems has never been documented. This report is intended to assist engineers, utility managers, and planners in selecting a membrane process for desalting recycled water.

There are many factors that a utility must consider when selecting a desalting system for a recycled water application. Both EDR membranes and RO membranes with MF pretreatment can be successfully applied to recycled water desalination at similar lifecycle costs. Because the costs are so similar between the two processes, utilities will need to determine if there are any additional plant-specific factors that could impact the process costs. A utility may also want to consider some of the non-economic factors that separate the two desalination technologies, such as removal of constituents other than salt, carbon emissions, potential hazards, and process reliability.
(2012, 81 pages, 08-17-1)

Member price: 25.00
Foundation subscriber price: 15.00
Non-member price: 45.00