Here's how BWS plans to turn seawater into drinking water

Decades ago, the state shut down its experimental water desalination plant in West Oʻahu. Now a city venture is about to breathe new life into the idea.

Building off the state's demonstration project, which tested out three processes of desalination in the 1990s, the Honolulu Board of Water Supply is now planning the construction of a small plant at Campbell Industrial Park, which would be able to turn seawater into drinking water.

The land was conveyed to the state by the federal government at no charge, with the stipulation that it would be used to build a seawater desalination plant.

The project is currently in its design phase. Groundbreaking is over a year away.

Barry Usagawa, a program manager for the Water Resources Division of BWS, said the plant will use reverse osmosis to condition the water.

"We have two saltwater wells that we drilled on the property. They pump it [at a] pretty high pressure through the membranes, and out comes freshwater on one side," Usagawa explained.

"On the other side is brine, which is then injected into the shallow caprock aquifer just off the site."

The process should not affect the local environment.

Usagawa believes movements toward desalination are not only beneficial but also necessary for Hawaiʻi's future. He said the state has been seeing lower rainfall trends in recent years and should not be fully reliant on groundwater.

"Our strategy is to diversify our water supplies: fresh groundwater, desalination, recycled water plus conservation, some storm water capture," Usagawa said.

"The more diverse we have our water supplies, the more resilient we'll be to climate change-induced droughts, which is what's being forecasted."

The large-scale project has no shortage of complexities and challenges. The main obstacle has been the cost of powering the desalination plant. BWS hopes to build a photovoltaic farm on the Campbell property to offset costs.

It plans to get the desalination plant online in late 2026.

This interview aired on The Conversation on August 8, 2023. The Conversation airs weekdays at 11 a.m. on HPR-1. This interview was adapted for the web by Emily Tom.