Water Reuse

Honolulu, Hawaii

In August 2000, the city of Honolulu opened its first reuse facility on Oahu and, at 13 million gallons per day, it is the largest in the Hawaiian Islands.  The Honouliuli Water Recycling Facility (HWRF) was built to preserve limited potable water and to satisfy a 1990s decree madating the city reduce the amount of wastewater effluent it discharges into the Pacific Ocean.

The HWRF was built adjacent to the Honouliuli Wastewater Treatment Plant so that it could "T" into the plant's effleunt outfall.  The facility produces two grades of high-quality recycled water, R-1 water, which is used for landscape, agriculture, and golf course irrigation, and reverse osmosis water (RO) which is used for industrial purposes, such as boiler feed water and ultra-pure process water.  One industrial customer of RO water saves the island 600,000 gallons a day of drinking water.  With all the industrial users combined, it saves a whopping 2.5 million gallons a day of drinking water.

Switching to RO water also saves the industries money.  When rain filters through the lava structure in the ground, it picks up between 60 -70 parts silica per million gallons in the drinking water.  The silica turns into glass when it enters the boilers, costing the power plants and refineries a substantial sum of moeny to demineralize the water to remove it.  The HWRF, on the other hand, reduces the silica concentration to about 1 part per million gallons of water.  Thus, industries spend much less to demineralize the RO water.

When the HWRF first opened, irrigation users such as golf courses paid only 25 pcents per thousand gallons of R-1 water.  Over a three-year period, the rate was increase to 65 cents.  Providing water at such low prices enticed users to replace groundwater with recycled water for nonpotable uses.  The R-1 water users are pleased with the results.  Chlorides were reduced from 800-1,600 for groundwater to less than 300 chlorides for recycled water, and choride sensitive vegetation is now plentiful on the golf courses.

Because of the dissolved nitrogen and phosphorus compounds in the R-1 water, the golf courses have reduced their purchases of commercial fertilizers.  When other Oahu golf courses have to reduce water use during the summer season, the HWRF-watered golf courses continue to irrigate with the drought-proof recycled water supply.

Honouliuli Water Reclamation Facility

Source:
McKenzie, C. Wastewater Reuse Conserves Water and Protects Waterways. On Tap. Winter (2005): 46-51.