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A disinfection system using ultraviolet light as a disinfectant will likely curb high levels of bacteria from the Kailua wastewater treatment plant, resulting in fewer beach closures by the end of 2025, according to an official with the City and County of Honolulu.

It’s one of several upgrades to the city’s wastewater treatment plants, which process sewage from homes and businesses before discharging the treated water into the ocean.

Honouliuli Wastewater Treatment Plant in Ewa Beach began construction on a $517 million project last month to make the plant more energy-efficient. Waianae’s plant is being upgraded so that recycled water can be used for agriculture, according to director of the Department of Environmental Services Roger Babcock. 

In Kailua, upgrades include a crucial feature that the city says will help prevent beach closures that occur when the bacteria enterococcus exceeds regulatory limits.

Enterococcus isn’t necessarily dangerous on its own. But tracking its presence helps determine how much fecal matter is in the water since it lives in intestinal tracts of warm-blooded animals, . Swimming in water with fecal matter like gastrointestinal sickness, skin rashes or upper respiratory illnesses.

Last year, the enterococcus level exceeded limits on 13 days between April and May, and the state posted signage advising the public from April 20 through April 26. The city is required to tell the state Department of Health when bacteria levels spike above limits.

The state’s acting clean water branch supervisor, Bobbie Teixeira, said at the time that the city was downplaying concerns by not mentioning in its press releases just how high the enterococcus level was. The state issued its own press release on May 5 that said the enterococcus presence was six times the state limit and advised the public .

At a press conference later that month, the mayor denied that the city downplayed health concerns, and DOH director Kenneth Fink joined him in support. In June, the state fined the city more than $400,000 because its discharges had violated the terms of its , which is regulated by the state.

Wastewater that enters the plant goes through stages of filtering and chemical treatment before being discharged into the ocean. The new UV disinfectant stage will be near the end of the system. 

UV rays that emanate from submerged lights can disinfect it in seconds by altering bacteria’s DNA so that it can’t reproduce, Babcock said.

This will not be the plant’s first UV disinfection system. 

A system was in place until 2009. But heavy water flows flooded the channel and damaged electronics on top of the UV lights. 

A 2017 estimated the cost of replacing the system at $500,000 or so. But now, the projected cost of a new system is $11 million, about 20 times more expensive than the EPA’s estimate, paid for with money allocated in last year’s city budget. 

Part of the reason for the disparity is that construction costs in general have gone up, Babcock said. He said he wasn’t sure how the EPA came up with its estimate.

This version of the UV disinfection system won’t have the same risk of damage because the electronics will be placed outside the water flow, protecting them from flooding, Babcock said.

Last year’s bacteria spikes caused the federal government to step in, and the ensuing conversation among different levels of government led the department to brainstorm potential solutions. It settled on installing a new UV disinfectant system because it would directly target bacteria, Babcock said.

During a budget hearing last week, council member Esther Kiaaina pressed Babcock on when the project would be complete and asked how the problem will be mitigated until then. 

“I just want to make sure because I get concerned constituents with regard to the exceedance levels,” she said. 

Babcock confirmed the project’s completion deadline as being the end of 2025, with the state Department of Health and the EPA.

In the meantime, he said, “we have a whole series of things that we do” to mitigate the problem.

That includes setting certain chemical doses in other stages of the treatment process to ensure that the level of enterococcus remains acceptable.

“It’s an ongoing challenge,” he said.