Water Treatment Primer 1

Surging population, energy demands, and climate change will push us, ever more urgently, to find new approaches to meet growing water demands. Most often, this will involve harvesting lower quality or impaired water supplies (e.g., seawater or brackish groundwater) as a source for drinking water. Recently desalination using membrane-based processes (e.g., reverse osmosis [RO], electrodialysis [ED], and nanofiltration [NF]) has shown promise for providing additional sources of fresh water across the United States. However, the current membrane separation processes are commonly energy intensive and produce large volumes of concentrated brine which poses unique challenges. Particularly in land-locked urban center brine disposal often relyes on surface water discharge or deep-well injection which pose economic and practical difficulties for wide-spread adoption of such technologies. Thus, there is an urgent need for energy-efficient desalination technologies that reduce the amount of concentrate produced, or identify cost-effective solutions for concentrate management.

The University of Tennessee, Knoxville (UTK) received funding from the Bureau of Reclamation (Reclamation) in September 2013 to investigate a novel salt and organic removal technology. Using microbial electrolysis cell (MEC) technology and salt removal via capacitive deionization (CDI) to remove organic compounds present in produced water was investigated. This project was conducted in collaboration with CAP Holdings Company (CHC), which provided expertise in CDI technology. Converting soluble organic compounds via MEC was coupled to salt removal via CDI, providing a proof of principle for synergistic salt and organic removal. Hydrogen was generated by MEC from organic compounds and used to produce renewable electricity via a polymer electrolyte membrane (PEM) fuel cell , which was then used to power the CDI cell to achieve deionization.

This is an introduction to water treatment systems and technology. It is not a design manual or an exhaustive treatise. It is intended for engineers who are not regularly involved in water treatment projects, but who are interested in learning some of the basics involved. Criteria to be followed in determining the necessity for and the extent of treatment are discussed here, as are procedures applicable to the planning of water treatment projects.