Faulty disinfecting equipment allowed E. coli bacteria to be present in drinking water in the Aina Koa area, the Honolulu Board of Water Supply announced on Saturday.

The presence of the dangerous bacteria in drinking water is a violation of the federal Total Coliform Rule, which established minimum safety standards for drinking water.

BWS officials said a "bacterial presence" was initially detected on Thursday in a test sample collected on Wednesday from the Aina Koa Neighborhood Park area (E. coli testing takes 24 hours to complete). Another follow-up set of samples taken on Thursday indicated lower-than-normal chlorine levels.

On Friday, one of the follow-up samples was also found to have been contaminated with E. coli.

During a subsequent inspection of all Aina Koa well stations and reservoirs, the BWS staff traced the problem to a "breakdown" in equipment that adds chlorine to water at Aina Koa Well II. Repairs to the system were completed on Friday and follow-up testing revealed no further evidence of the bacteria.

The water board reported the positive test to the state Department of Health on Friday. The department later informed BWS officials of the federal violation and issued a Tier 1 Notice of violation as part of standard procedure. Such notice required BWS to inform the public about the contamination.

E. coli is found in human and animal waste or in tropical, subtropical or temperate soils and can cause diarrhea, cramps, nausea, headaches or other ailments in humans. The bacteria can be especially harmful to infants, young children, the elderly and people with severely compromised immune systems. E. coli in water can be destroyed by boiling or chlorinating.

BWS advises anyone at increased risk of being affected by E. coli to contact their health care provider.