Monterey slant well project gets grant to assess bacteria removal

US utility, American Water, has picked up more than US$ 200,000 in grant support from the WateReuse Research Foundation to assess pathogen removal during the collection of seawater for desalination through sub-surface slant wells.

The US$ 330,000 project will be carried out at a test slant well currently under construction in Monterey County, California by American Water’s subsidiary, California American Water.

“This research is important to the entire water industry,” said American Water’s Dr Zia Bukhari. “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,” Bukhari added.

Slant wells are drilled diagonally beneath the beach and extend under the ocean floor to draw water through sand,and thereby mitigate the impact on marine life associated with conventional open intakes. Drawing water through sand provides a filtration step in the purification of ocean water that can reduce the need to remove bacteria before and after desalination. The research project proposes to look at human pathogens to see what degree of treatment is achieved in slant wells and to define further additional steps to ensure pathogens are removed.

“Slant wells are known for their benefits to marine life. But, they may provide an additional benefit of pathogen reduction,” said Cal Am director of engineering, Rich Svindland. He added: “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.

“Our findings will be extremely valuable for water resource managers and policy makers across the country.”

Cal Am recently received a US$1 million, California Department of Water Resources grant to support the test well project. Cal Am has included desalination as part of a proposed multi-sourced approach to ending water shortages and reducing extraction from the Carmel River.

The state’s regulatory bodies, including the State Water Resources Control Board and the California Coastal Commission have backed the use of slant wells. The Monterey Bay National Marine Sanctuary and the National Oceanic and Atmospheric Administration have both issued recommendations that desalination projects deploy subsurface intakes where they can.