Bahman sheikh water reuse consulting

Client: HawaiI community foundation



Hawaiʻi has historically received ample precipitation to support its natural habitats and the built environment in harmonic balance. That balance is at risk of tilting in the direction of water shortages in the future because of increasing demand for water and projected decreasing supply from rainfall.

Water recycling is one of the ways in which the historic water resource balance can be restored and maintained. The potential to achieve the needed increase in water reuse is great because the identified barriers are amenable to removal with legislative initiatives, regulatory reforms, and attitudinal changes. Such remedies have been shown to be successful in other states and their experiences can serve as useful models to emulate for Hawaiʻi.

Top water cycle managers in Hawaiʻi have recognized the impact of climate change and future population increase on the state’s water supply. Facilitated by Hawaiʻi Community Foundation, the Freshwater Council set a goal of adding 100 million gallons per day (MGD) of new water supply by the year 2030—from water reuse, conservation, and groundwater recharge. Water reuse is expected to provide over 30 MGD of the total by 2030.

Currently, most water recycling in Hawaiʻi occurs on the islands of Oahu and Maui, and most of the recycled water produced is used for golf course irrigation. Other users of recycled water are industries, agriculture, and landscapes. Barriers to expanding water reuse in Hawaiʻi include economic/financial constraints, regulatory obstacles, institutional impediments, infrastructure inadequacies, and social attitudes. All of these challenges are amenable to being overcome, as shown with examples from several other states and overseas.

Opportunities for future expansion of water reuse in Hawaiʻi lie in several new arenas. A major opportunity for scaling water reuse lies in agricultural irrigation with R-2 and R-1 recycled waters. Agriculture is very important to Hawaii’s economy and consumes a large fraction of the total water used by all sectors.  Furthermore, recycled water can be used for irrigation of food crops over currently fallowed lands that formerly produced sugarcane and pineapple. Use of recycled water in agriculture will help meet the state’s goal of increasing local production of food crops.












Decentralized water reuse, in new developments, especially in high-rise buildings provides another arena for pushing water reuse forward. On-site water reuse—another term of art for “decentralized reuse”—is an especially effective water conservation measure in densely populated residential and commercial districts in urban areas such as Honolulu, resulting in 40 to 80 percent less demand for the building’s water requirement from the municipal network. Feasibility and economic viability of on-site reuse has been demonstrated in major metropolitan areas, including New York City, San Francisco, Sydney, and Melbourne.

Another promising arena, in terms of volume and in the long-term vision, is groundwater replenishment with recycled water. Managed aquifer recharge, using recycled water, has been a long-standing practice with an unblemished record of safety in California, Arizona, and Texas. This use of recycled water for groundwater replenishment is currently not included in the allowed categories listed in the water reuse guidelines administered by the Hawaiʻi Department of Health, Wastewater Division. Adoption of specific guidelines and regulations, defining the required water quality and the recharge process is necessary to open this use of recycled water in order to combat future overdraft of coastal aquifers and consequent intrusion of seawater into the groundwater supplies.

Several strategies are offered for accomplishment of the 30+ MGD by 2030 goal, including legislative initiatives, regulatory updates, financial support and subsidy, demonstration projects, and public outreach and education.

Accomplishment of the 30 MGD by 2030 goal is feasible—much larger goals have been accomplished in other states when the need for new water supplies was broadly recognized. Recommendations for specific actions are offered to guide the path to arrive at—and possibly even exceed—that goal over the coming decade. The most effective first steps toward accomplishing the 30-by-2030 goal are: (a) legislation, (b) master planning, (c) demonstration projects coupled with public outreach and education, (d) financing, (e) market studies, (f) regulatory updates, and (g) progress toward implementation of projects leading to delivery of recycled water to customers. 

City of Honolulu, on the Island of Oahu where 64 % of the State’s recycled water is currently generated and reused.

To contact us:

Phone: 555-555-555

Fax: 555-555-5555


Text Box: Photo Credit: Monterey One Water

All Water Is Recycled