Kihei Effluent Reuse

 


INTRODUCTION
County of Maui Wastewater Reclamation Division Logo

Kihei lies on the dry south side of Maui.  Potable water for the area must be piped over ten miles from water wells drilled into the ‘Iao Aquifer near Wailuku.  Approximately 65 percent of this water is used by the community for irrigation with the remainder ultimately ending up in the sewer system. This wastewater is then treated and disposed at the Kihei Wastewater Reclamation Facility (WWRF).

In the past, the County of Maui has had difficulty finding users for reclaimed water from the Kihei WWRF.  The primary drawback has been the high cost of conveying the treated effluent to individual users.  However, through the collective efforts of surrounding landowners, potential users and the County, an effluent reuse system consisting of storage and transmission facilities was constructed that met the needs for all parties involved. The goal of the project was to establish a reuse system that was compatible with existing activities, providing beneficial uses for the community, minimizing adverse environmental impacts and be economically feasible.

 

KIHEI WASTEWATER RECLAMATION FACILITY (WWRF)

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The Kihei WWRF is an activated sludge treatment facility that currently has a peak dry weather capacity of 8.0 million gallons per day (mgd). The facility has undergone major upgrades in its treatment capabilities with the addition of flocculation and chemical feed units, effluent filtration, ultraviolet disinfection, and renovations to the operations building. The plant is capable of producing high quality effluent, designated as R-1 by the Hawai‘i State Department of Health (DOH) Standards. Because R-1 effluent is the highest grade of reclaimed water by DOH standards, it has minimal restrictions for reuse.

The Kihei WWRF currently reclaims between 40 and 50 percent of the wastewater it treats, which is typically between 1.6 and 2.0 million gallons per day. The remaining treated effluent is discharged into injection wells located on the grounds of the WWRF, where it percolates into the ground. It is envisioned that the Kihei WWRF will eventually reclaim 100 percent of its flow as public acceptance and demand for the high quality effluent increases in the future.

PROJECT DESCRIPTION

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The County of Maui has constructed major elements of the Kihei Effluent Reuse System which includes its storage facilities and a major portion of its transmission and distribution system. These improvements have been installed in two projects: the Kihei Effluent Reuse Core System and the Kihei Effluent Reuse Distribution System, Phase I. The initial project, the Effluent Reuse Core System, qualified as an innovative project for a 100 percent low interest loan from the State Revolving Fund (SRF), administered by the Hawai‘i State DOH.

Kihei Effluent Reuse Core System

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The Kihei Effluent Reuse Core System included modifications of existing facilities at the Kihei WWRF and new improvements.  Major elements at the Kihei WWRF incorporated into the reuse system included the effluent pumping station, equipped with two 1500 gpm pumps, and the 1.8 million gallon (MG) effluent storage basin.  The existing effluent storage basin was rehabilitated and retrofitted with a polypropylene liner and floating membrane cover system to maintain the high quality of the treated effluent produced at the reclamation facility. The membrane liner and cover protect the effluent from debris and contaminants, and reduce the potential for algae growth.

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The new improvements were designed to operate in concert with the existing reclamation facilities, and are capable of functioning under expanded operating conditions as the plant capacity is increased in the future.  New improvements included the construction of an elevated 1.0 MG reinforced concrete reservoir in the hillside above the Kihei WWRF.  The elevated tank allows gravity to pressurize the system, thus eliminated the need for mechanical pumping.  The reservoir is fitted with an aluminum geodesic dome cover that eliminated the need for interior columns and footings within the reservoir, and the resulting cost savings allowed for the installation of a high quality tank lining system.  In addition, an 18-inch ductile iron pipeline was constructed to connect the storage reservoir to the reclamation facility.

The storage and transmission system was also equipped with remote pressure and flow sensors and level controls that communicate with the Kihei WWRF control station. Due to the reservoir’s remote location, level sensors at the tank utilize solar powered radio transmitters to communicate with the WWRF control station, thus eliminating the need for conventional power and communication lines. The telemetry system enables system operation and status checks through the reclamation facility’s Supervisory Control and Data Acquisition (SCADA) System. The SCADA system is programmed to start and stop the effluent pumps and to control valves that permit irrigation of the Elleair Maui Golf Club and the Monsanto Corporation’s seed corn operations.

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The Effluent Reuse Core System was put into operation prior to completion of all construction, so that it could continue to serve Monsanto Corporation’s seed corn operations and the Elleair Maui Golf Club. Cooperation between effluent consumers, the County and the contractor allowed virtually uninterrupted service during the construction period. The total project construction cost for the Kihei Effluent Reuse Core System was $3.2 million. Total project construction time was 12 months with the project substantially completed in April 1998.

Kihei Effluent Distribution System, Phase I

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Community interest in utilizing reclaimed effluent and the surplus funding available from the initial project prompted the County of Maui to extend the effluent distribution capability of the Kihei Effluent Reuse Core System. The Kihei Effluent Distribution System, Phase I was initiated during the construction phase of the Core System. Planning, design and bidding of the project was accomplished prior to the completion of construction for the Effluent Reuse Core Project.  One of the goals of the project was to complete construction of the distribution system before the completion of the Kihei Community Center, allowing the effluent to be used for the establishment of the playfields being constructed at the Center.

The Phase I Distribution System included the extension of the effluent transmission line from the Kihei WWRF in the makai direction across Pi‘ilani Highway, then northward along the proposed North-South Collector Road corridor to the Kihei Community Center site. Approximately 6,200 linear feet of 12-inch, and 1,700 linear feet of 18-inch, ductile iron pipe was installed for this project. The system serves the Kihei Community Center, Kihei Elementary and Lokelani Intermediate Schools, Haggai Institute and the Pi‘ilani Commercial Center.
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The effluent line was also outfitted with fire hydrants to aid firefighters in control of brushfires that frequently occur in the area. Per Hawai‘i State DOH standards, the fire hydrants are painted purple to identify them as part of the reclaimed water system.

The construction cost for the Kihei Effluent Distribution System, Phase I, was $682,000. Total construction time was 8 months, with substantial construction completed in December 1998. The contractor for the project was Goodfellow Brothers, Inc.

CONCLUSION

The Kihei Effluent Reuse System is the first application in Hawai‘i of an effluent reuse system pressurized by an elevated closed reservoir, making the effluent available to customers on a continuous basis.  Customers can simply connect to the system and use the effluent without the use of booster pumps.  The system has met its goal of providing the County of Maui with a system that is beneficial to the community by preserving its potable water resources, and utilizing reclaimed water for irrigation of parks, landscape areas and a golf course, and for fire protection. The reclaimed water is also used by a major agricultural operation, Monsanto Corporation, for the production of high quality seed corn that is marketed worldwide. The system has proven to be easy to operate and reliable, and has met the needs and expectations of the County.

For more information on the Kihei Effluent Reuse System, contact Steve Parabicoli, Maui County Wastewater Reclamation Coordinator at phone (808) 270-7426 or e-mail: steve.parabicoli@co.maui.hi.us.