Hilo Wastewater Treatment Plant Rehabilitation and Replacement Project
PLANNED IMPROVEMENTS
Site Layout of the Hilo Wastewater Treatment Plant, Pre-Construction
Site Layout of the Hilo Wastewater Treatment Plant, Post-Construction
Headworks
A new headworks facility will completely replace the existing structure. New screening, grit removal, flow metering, and odor control systems.
Primary Sedimentation Tanks
Repairs and replacements of aging concrete, valves, sludge collection equipment, and odor control systems to maintain efficient solid separation.
Secondary Clarifiers
Upgrades to valves, sludge collection, effluent launders, and pumps to enhance water clarification and sludge removal.
Effluent Disinfection
Improved chemical feed, monitoring, and control systems for more effective disinfection of treated wastewater.
Sludge Blending
New blending tanks and mixing systems to optimize sludge processing before thickening.
Sludge Thickening & Dewatering
Construction of a new solids handling building with modern thickening and dewatering systems to improve biosolids management and odor control.
Anaerobic Sludge Digestion
New digesters and control systems to enhance sludge stabilization and biogas management.
Pump Stations
Replacement of on-site pump stations to ensure smooth wastewater flow and system efficiency.
Electrical System Upgrades
Modernization of the plant’s electrical infrastructure, including a new switchboard, backup generator, and improved climate control for electrical rooms.
Instrumentation & Control
Installation of a new SCADA system for automated monitoring and control of plant operations.
General Site Improvements
Utility extensions, paving, grading, and a new warehouse to support plant operations.
PROJECT MILESTONES
🟢
NTP
ISSUED
02/2025
🚧
CONSTRUCTION
START
7/2025
⭐
HEADWORKS
SYSTEM
10/2026
⭐
PRIMARY
FACILITIES
DATE TBD
⭐
SUBSTANTIAL
COMPLETION
DATE TBD
🎉
CONSTRUCTION
FINISHED
DATE TBD
NEWS
FAQs
Will the upgraded plant be able to handle more wastewater?
The project restores or replaces critical facilities with reliable modern equipment, and new building structures.
Did the County consider other methods besides upgrading the existing plant?
Alternative technologies and approaches were evaluated during the planning phase of the project.
What level of treatment does the Hilo WWTP provide?
The Hilo WWTP provides secondary treatment with disinfection, as required by the NPDES permit.
Why did the County issue an emergency proclamation for the Hilo Wastewater Treatment Plant?
The emergency proclamation enables the County to take quick action to protect public health if the Hilo Wastewater Treatment Plant faces infrastructure failure during rehabilitation.
PROJECT TEAM
Contractor
Nan Inc
Builds the project using the right materials and crew, making sure it’s done safely, correctly, and on time.
Engineer of Record
Carollo Engineers
Designs the project, ensures it meets all safety rules and regulations, and follows approved plans.
Construction Management
TBD
Keeps the project on schedule and organized from start to finish.
CONTACT US
✉️ cohdem@hawaiicounty.gov
📞 808-961-8099