WRRCSR No.09:00.88 Wastewater Reuse By Irrigation in Hawai'i: May 1989 Update

Abstract

A statewide survey was conducted to detennine the nature and extent of wastewater reuse by irrigation in 1989. An average of 13.985 mgd (million gallons/day) of wastewater is applied to 2115+ acres. Acreages are difficult to ascertain because with sugarcane much of the wastewater is highly diluted with other waters and distributed broadly to indeterminable acreages. The 1989 data were compared with an earlier survey conducted in 1977. Current reuse is approximately double the 7.18 mgd recorded in 1977. The two primary reuses statewide are for sugarcane and golf course irrigation, utilizing 7.382 and 6.288 mgd respectively. Since 3.5 mgd of the effluent applied to sugarcane is utilized irregularly, it is difficult to suggest any trends. Reuse on golf courses, on the other hand, has tripled from the 2.06 mgd in the earlier survey. This increase is attributable to gains on all islands but particularly on Maui. In the state, there are 24 treatment plant/reuse facilities of which twenty use domestic wastewater and four utilize farm animal wastes. On an island basis, Maui and O'ahu have the highest wastewater reuse, with 6.185 mgd and 5.072 mgd respectively, followed by Kaua'i (2.09 mgd), Hawai'i (0.528 mgd), and Moloka'i (0.11 mgd).