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EVALUATION OF PERCOLATE QUALITY RESULTING FROM RECYCLED WATER IRRIGATION IN CENTRAL OAHU
Author: Ronald W. Crites, Erwin M. Kawata and Woodie M. Muirhead
Date: 10/05
2004 WEBTEC Technical Sessions

The Honolulu Board of Water Supply (HBWS), the municipal water utility for the island of Oahu, State of Hawaii, is exploring the use of recycled water as one of their water supply options. Opportunities exist for irrigating R1 water over the potable water aquifers in Central Oahu, but the possible impact on the aquifers is not known. To evaluate the possible impact, the HBWS is conducting a scientific study to determine the level of constituent removal from R1 (disinfected tertiary) water through the soil treatment in Central Oahu. A field research and demonstration project was developed to study the safety, efficacy, and value of recycled water for turf irrigation. Twelve plots were developed in Central Oahu Regional Park to compare sprinkler irrigation of recycled water and control groundwater. Constituents monitored in the applied water plots, the control plots and the 12 percolate samples include nutrients, inorganic minerals, bulk organics, metals, NDMA, two pesticides, and the endocrine disrupting compounds Estradiol and Estrone. The percolate qualities were not significantly different for the bulk and trace organics, including NDMA.