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Water Reuse in Hawaii

Fresh water is our most precious natural resource. More than anything else, our natural supply of fresh water makes Hawai‘i the special place that it is. With the growth of our island state, we are pushing the limits of our available natural supply. That's why water conservation must become part of our daily lives.

In Hawai‘i, we've been searching for ways to conserve our water supply. Water recycling (or reuse) is one of the most effective and proven methods for doing so. Typically, we've used water once and thrown it away. But now more and more people are using water over and over again.

You probably don't realize it, but over 100 million gallons of treated water are released into the ocean everyday. It's perfectly good water. It's just been used before, and is commonly referred to as wastewater. But it's only wasted if we don't use it again.

 

Why is Water Recycling Important?

The amount of water used to irrigate farm crops, golf courses, and residential and commercial landscaping is more than 70 percent of the drinking water we use. That's about 750 million gallons a day!

When wastewater is treated for recycling, some nutrients are left in it that is good for plants. As a result, recycled water is great for irrigating most landscaping, crops and golf courses. Because of it's nutrient content, recycled water is actually better suited than drinking water for some of the applications where drinking water gets used the most.

When recycled water is used for irrigation, more of our natural supply of drinking water is made available where we need it the most - for people to drink, for cooking, for washing, and for the 'aina.

 

Laws and Regulations Govern How Recycled Water is Produced and Used

In Hawai‘i, there are 3 classifications of recycled water based on regulatory definitions. The classifications indicate levels of purity and determine how the water is carefully monitored and the water is not recycled if it does not meet the required level of quality.

R-1 is the highest quality recycled water. This water has gone through filtration and disinfection that makes the water safe for use on lawns, golf courses, parks, and other places that people frequent. In Hawai‘i, more and more projects are using R-1 water.

R-2 is slightly lower quality recycled water. R-2 is secondary (biologically) treated wastewater that has also been disinfected. Its use requires more caution and restrictive controls than R-1 water.

R-3 is the least pure class of recycled water. R-3 quality water is wastewater that has been treated to the secondary level. It can only be used for irrigation at places where people rarely go.

 

Where Recycled Water is Applied

Recycled water is utilized on most of the main islands in Hawai‘i. Golf courses, agriculture, and landscapes are irrigated with recycled water. Some of the golf courses that use water include the Experience at Koele, Ka‘anapali Golf Course, Hawai‘i Kai Golf Course, Kaua‘i Lagoons and Waikaloa Resort.

Agricultural uses include seed corn irrigation on Maui and Kaua‘i and at Hawai‘i Reserves on O‘ahu where bananas, papayas, and ornamental plants are grown. Landscape irrigation projects include Kalama Park and the Kihei Public Library on Maui, Mauna Loa Highway beautification on Moloka‘i and the Brigham Young University-Hawai‘i campus on O‘ahu.