Honolulu Sand Island Wastewater Treatment Plant

Serving the Community with Natural Wastewater Treatment Options

Hawaii is a place where key values include a passionate commitment to the protection of the environment and the pursuit of sustainability. The natural beauty of the islands is cherished by residents and is an irresistible lure to millions of visitors from around the world. Preserving these natural assets is essential.

The City and County of Honolulu (CCH) faces the constant challenge of expanding and improving the collection, treatment, disposal and recycling of waste materials. In 2002, the CCH entered into a public-private partnership with Synagro to design, build, and operate (DBO) a bioconversion facility.

The facility provides digestion, dewatering, and heat drying and pelletization of biosolids for the Sand Island Wastewater Treatment Plant, Hawaii’s largest plant.

Defining a Sustainable Biosolids Management Solution

Goals set for the facility include compliance with EPA regulations, minimizing the need to place biosolids in landfills and implementing a Class A recycling program that meets the standard for exceptional quality. Timing of the project was crucial because the city’s Waimanalo Gulch Landfill was projected to reach its permitted capacity in 2003.

Synagro applied its expertise to review, analyze and assess several options for this project. Ultimately, the best solution for this community was anaerobic digestion, centrifuge dewatering and heat drying and pelletization.

Benefits Include Conversion to Quality Fertilizer

CCH has experienced significant benefits from the public-private partnership that resulted in the in-vessel bioconversion facility at the Sand Island wastewater treatment plant:

  • Landfill disposal of biosolids decreased from 100 percent to only seven percent
  • The need to expand Oahu’s landfill are minimized
  • Biosolids are now converted into a commercial-grade, Class A exceptional quality fertilizer for agricultural and commercial use on the island, supporting long-term sustainability goals
  • Renewable biogas used by the facility reduces the island’s dependence on imported fossil fuels

Partnering with the Honolulu Community

Synagro staff members regularly meet with CCH officials and local businesses to participate in ongoing efforts to preserve the environment and enhance sustainability efforts. Synagro also provides product donations and financial support to a variety of community organizations.

Synagro works with the Honolulu Sand Island Wastewater Treatment Plant to reduce landfill disposal of biosolids by 93% annually