Water is a precious, limited resource. Though Hawaii is blessed with a humid climate that should make water abundant, because of recurring drought conditions and water fouling at Red Hill, we have a current crisis. Climate change is forecasted to make Hawaii drier in the future. It is scary but it means we might be running short of potable water soon. The bottom line is we need to reduce demand of precious potable water.

To have a sustainable future, we need solutions that solve the underlying problems and not only short-term fixes. We must change our perception about our role in treating water like the precious resource it is through conserving, as well as adding new efficient technologies.

Smart conservation measures and innovative technologies need to go hand in hand. The biggest personal change is to conserve as though we will face drought regularly, as the Honolulu Board of Water Supply says. When we open the faucet, we need to know what overuse looks like, and the impact to the environment and our community. We need the willingness to implement technologies that save water but might cost a bit more money or effort than what we are used to.

Increased water recycling provides another important conservation of water. The existing 14-million-gallons-per-day Honouliuli Water Recycling Facility supplies recycled water for large irrigation and some industrial applications, but the distribution system limits the supply to the Ewa-Kapolei area. Installing new islandwide recycled water from central treatment plants would be very costly and energy-intensive to operate.

A less-costly way to recycle water is to increase residential and commercial onsite wastewater treatment. Advantages of onsite treatment include keeping recycled water close to where it was first used or harvested. This avoids costly distribution to pump recycled water over long distances from central wastewater treatment plants. Over the past few years, the technologies and regulatory standards to assure quality of onsite treated water have become available. Onsite wastewater recycling can be valuable to reduce the demand for potable water for some functions, such as irrigation, toilets and other nonpotable uses in and around buildings.

A current pilot project here in Hawaii has verified that state-of-the-art on-site wastewater treatment technologies are cost-effective and can be readily installed. The onsite treatment equipment is certified under a new national standard. The treated water resembles rainwater quality, and can be used without limits outdoors, and for specific indoor functions. We can safely use onsite recycled water for irrigation, toilet flushing or hosing down the driveway, to name a few applications.

The potential is high and important. In Hawaii, we use 20% to 30% of our domestic water supply for irrigation and outdoor consumptions. Indoors, the Environmental Protection Agency states, toilet flushing alone can use up to 30% of water consumption.

Recycling water for these two uses could safely replace up to 50% of our domestic potable water demand with recycled water, taking pressure off our municipal water supply. Imagine what that could mean for sustainability of our water use in Hawaii.

Summarizing: On-site wastewater treatment needs to be promoted since it helps Hawaii to overcome the water crunch. It provides valuable recycled water close to the point of consumption thereby keeping local distribution pipes and limited replumbing of buildings doable and affordable. The good news is that our quality of life will not be reduced. In fact, by investing in more sustainable water use, we are helping the planet and save money.

Manfred Zapka, Ph.D., P.E., is a professional engineer licensed in Hawaii, with expertise in healthy and sustainable buildings, infrastructure and technology.