Study of Cesspool Conversion Technologies and Financing in Hawai‘i

Research will be conducted in the following categories: biological wastewater treatment; innovative primary treatment for carbon diversion; thermal hydrolysis pre-treatment of sludges; anaerobic digestion; co-digestion of fats, oils, and grease (FOG); food waste; bioplastics; sludge dewatering; on-site wastewater treatment including passive denitrifying absorption systems and constructed wetlands; water recycling; membrane bioreactors; groundwater infiltration into sewers; stormwater runoff management including green roofs; and biofiltration systems.

Study of Cesspool Conversion Technologies and Financing in Hawai‘i

Carollo Engineers Inc

01/01/2020 – 12/31/2020

In 2017, the Hawai‘i State Legislature passed Act 125, which bans all cesspools by 2050. This will necessitate the upgrade/replacement of 88,000 residential cesspools statewide. The projected estimated costs range from $1.7 to $4 billion. However, to make informed choices, we need to develop knowledge on the technical options, associated costs, and finance methods avialable. The legislature also created the Cesspool Conversion Working Group (via Act 132 in 2018), which initiated some research projects, including a technology assessment and screening process for available and emerging technologies and a finance options investigation. This project will conduct research to assist on both of those efforts. An updated cesspool conversion technologies evaluation matrix will be created that includes an evaluation of various treatment processes, disposal alternatives, and combinations thereof. It will also include conventional technologies, innovative technologies, and emerging technologies; as well as design criteria, site restrictions, expected performance, and capital and operating and maintenance costs. At the conclusion of this study, our goal is to review and write an update to the Department of Health 2008 Onsite Wastewater Treatment Survey and Assessment report, and assist with the determination of cesspool replacement funding options and evaluation.