Hensel Phelps achieved a major milestone at the $436 million Sand Island Wastewater Treatment Plant in Honolulu, Hawaii, with the successful launch of clean fluid startup on February 24, 2026. This achievement marks the transition from construction into active system validation and represents a critical step in the startup, testing and commissioning of one of the largest membrane bioreactor (MBR) wastewater treatment facilities in North America.
Extensive Planning and Coordination Enabled Startup Success
This milestone reflects the strength of early planning and disciplined execution across complex systems. Clean fluid startup required extensive collaboration with more than 50 different manufacturers, suppliers and trade partners, which helped the Hensel Phelps team to develop the detailed startup plan, sequence of work across process areas, and verify that all systems would meet project requirements for the City of Honolulu.
What Clean Fluid Startup Means for Wastewater Treatment Commissioning
Following functional completion testing, the project advanced into clean fluid startup, where clean water was circulated through new systems to confirm safe and reliable continuous operation for five days without disruption. During this period, all typical control strategies and operational sequences were exercised. Testing included continuous operation of pumps, blowers, valves, screens, and monitoring systems, as well as input/output (I/O) checkout to verify communication with control panels and the plant’s Supervisory Control and Data Acquisition (SCADA) system.
This phase presented several challenges, such as coordinating multiple teams, sequencing system energization, completing I/O checkout across integrated control systems, maintaining equipment reliability during extended clean water operation, and identifying discrepancies between operations and maintenance (O&M) documentation and actual system application. These findings are being addressed through updates and incorporation into the O&M materials.
Key Challenges During Startup and System Integration
Clean fluid startup also confirms integration of the MBR system – the primary design of secondary treatment – which includes permeate pumps, return activated sludge (RAS) pumps, air scour blowers, instrumentation, and controls. Sustained operation allowed the team to verify installation quality, identify issues early, and refine procedures ahead of process fluid startup.
Partnership with the City of Honolulu Wastewater Treatment Division
Hensel Phelps’ startup and commissioning team led a clean fluid startup in collaboration with the City of Honolulu’s Wastewater Treatment Division (WTD). The City’s officer‑in‑charge remains actively engaged by witnessing testing and reviewing documentation.
Next Phase: Process Fluid Startup and Final Commissioning
Completion of clean fluid startup positions the Sand Island project to advance confidently into Process Fluid Startup, biological treatment, and final commissioning. Hensel Phelps remains focused on delivering a safe, reliable, and high‑performance facility that will support long‑term operations for the City of Honolulu’s wastewater infrastructure for decades to come.
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