Some of the members of KCA’s board visited the Kihei Wastewater Treatment Plant on August 25.

Tom Johnson gave us a thorough walk-around and overview of how wastewater becomes R1 level (one step from drinkable) water for use in irrigation.

First there is a 7-mm filtration of course material.

Three centrifuges in this building separate water from heavier material.

The clarifier step.

Membranes filter out particles down to 10 microns, possibly 5.

Ultraviolet light is used to kill microbial content. This is modern technology that replaces the use of chlorine for disinfection.

One of the UV lights visible through the grate.

The effluent (outflow) from treatment is R1 water.

1.8M gallons of R1 water can be stored in this covered pond. About 2M gallons/day are used for irrigation by Monsanto, Kalama Park, and other South Kihei sites. Leftover R1 water goes into injection wells (about 1.5M gallons/day). The plant is built to handle 8M gallons/day.

Much of the discussion the past year around water quality at Cove Park has revolved around the pathways and content of the injection well water: how much reaches the ocean and where, what is the nutrient (nitrogen) content at that point? Tom said that the plant already applies aerobic and anaerobic treatment beyond what is required by law to reduce the amount of nutrients, but no studies have been done (unlike at Lahaina) to trace the paths of the water to the sea.

Maui County is the only County that requires the use of R1 water if property is adjacent to the R1 wastewater lines.  The property owners pay less than one third the cost of potable water for irrigation with R1 water.

There have been proposals to use some or all of the unused R1 water for the Wailea golf courses but it was considered too expensive for the county to build the pipelines. Hopefully construction of the pipelines will be a condition for future construction in Wailea (Wailea 670?).

What would it take to make the water R0 quality – potable? That is currently being studied in Lahaina.

The County staff was very accommodating and repeatedly suggested that if interested parties wanted to see the plant that they would be pleased to provide a tour.

More information about the plant, processes, and plans can be found at http://www.hwea.org/kihei-effluent-reuse/.

See also the Maui Nui Marine Resource Council’s Report on Options to Improve Wastewater Management in South Maui.