Water treatment site planned in Kunia
The $6 million facility, first of possibly several, will remove nitrates
WAILUKU » The Honolulu Board of Water Supply plans to build its first treatment facility to take out nitrates from drinking water at a well in Kunia.
The agency also is monitoring a couple of other wells in Central Oahu as potential future projects.
The treatment facility at Kunia Wells II, serving the community of Village Park, will cost $6 million and is designed to treat 5 million gallons of water a day, said Erwin Kawata, Board of Water Supply water quality director.
Kawata said the contaminant level of nitrates was at 7 milligrams per liter in 1998 and has dropped to 5 milligrams per liter, well below the 10-milligram maximum contaminant level of set by the U.S. Environmental Protection Agency.
"We're concerned about not exceeding the regulatory limit ... so we're trying to be proactive," he said.
Excessive levels of nitrates in drinking water have caused serious illness and sometimes death, but none are known to have occurred in Hawaii, Kawata said.
Serious illness in infants can take place due to the conversion of nitrate to nitrite by the body, interfering with the oxygen-carrying capacity of the child's blood and causing shortness in breath and blueness in the skin, the agency said.
Effects of chronic exposure to high levels of nitrate/nitrite include an excessive excretion of urine, increased starchy deposits and hemorrhaging of the spleen, the agency said.
The Board of Water Supply said it has found no proof that nitrates cause cancer.
Kawata said the agency is conservative in setting its contaminant levels.
Water experts said the source of nitrates in water can occur naturally through sewage and livestock manure especially from feedlots, showing background nitrate levels of 1 to 2 milligrams per liter.
The inorganic nitrates come from agricultural and lawn fertilizers, including potassium nitrate and ammonium nitrate.
Kawata said nitrate levels in water tend to be higher in former agricultural areas, sometimes at contaminant levels between 3 and 5.
Kawata said officials hope to start construction at Kunia Wells II by the end of the year and have the facilities constructed in a year and a half.
He said the method of extracting the nitrates, approved by the Environmental Protection Agency, involved a process called ion exchange and has been used in other states, including Pennsylvania and Illinois.
Kawata said the board is monitoring Kunia Wells I and a well station in Waipahu, both showing nitrates at 4.6 milligrams per liter.