American Water to study pathogen removal by subsurface intakes

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The research will be undertaken at the test slant well that is currently being built in Monterey County, California, by American Water subsidiary California American Water.

The WateReuse Research Foundation is contributing US$200 000 to the US$330 400 project.

“This research is important to the entire water industry,” said American Water’s Dr Zia Bukhari. “The effects of drought and climate change have increased interest in desalination as a technology for water supply. The science produced by this study will help define guidelines for water treatment when ocean water is collected through the environmentally-preferred approach of subsurface intakes.”

Slant wells, a type of subsurface intake, are drilled beneath the beach, at a diagonal angle, and extend under the ocean floor. These wells draw ocean water through layers of sand, thereby avoiding the impacts to marine life associated with traditional open ocean intakes. Drawing water through layers of sand also provides a first step in the purification of ocean water. The sand acts as a filter that can lessen the amount of bacteria removal required before and after the desalination process.

The American Water research project will look specifically at human pathogens (eg bacteria, viruses, parasites) to see what level of treatment is achieved through the slant wells and further define what steps will need to be taken in addition to reverse osmosis to ensure pathogens are removed.

“Slant wells are known for their benefits to marine life,” said California American Water director of engineering Rich Svindland. “But, they may provide an additional benefit of pathogen reduction. If this proves to be the case, there could be significant savings in pre- and post-treatment costs for desalination projects that employ slant well technology. Because this question has yet to be studied, our findings will be extremely valuable for water resource managers and policy makers across the country.”

The test well being constructed by California American Water will help determine the feasibility of slant wells as a desalination intake method on California’s Central Coast.

The research project team will consist of Bukhari as the principal investigator, with American Water’s Dr Patrick Jjemba and Elaine Howe of Trussell Technologies as co-principal investigators.