To achieve advanced high-purity oxygen treatment at its Central District Wastewater Treatment Plant (WWTP) on Virginia Key, FL, the Miami-Dade County Water and Sewer Department (WASD) upgraded their aging cryogenic system with vacuum pressure swing adsorption (VPSA) oxygen production units. The process improvements were implemented to meet federal consent decree effluent discharge requirements, update an aging cryogenic production system, and reduce operating costs. The project received a 2022 Water/Wastewater Merit Award from the Design-Build Institute of America’s (DBIA) Florida Region. Working with design-build lead PCL Construction, Wade Trim led the facility design for process mechanical, electrical, instrumentation and controls, architectural, acoustical, structural, plumbing, HVAC, civil/site work, stormwater, and fire protection.

The design combined one unit of the existing cryogenic system with two new, 90-ton-per-day VPSA units at the 143-MGD WWTP. This approach improved flexibility and redundancy for operations, while reducing energy consumption and related costs by approximately 20%. The overall control strategy integrated three different supply streams for various modes of operation: cryogenic as primary, VPSA as standby, and liquid oxygen as emergency. These technologies are staged during operation by controlling the inlet valve based on system pressure and headspace oxygen.

The design-build delivery model, supported by weekly project team meetings and early involvement of all stakeholders, enabled the facility to be completed a year ahead of schedule and on budget. Using separate design packages for the foundation and building, a master permit was obtained 2 months early, allowing construction to begin on the foundation while the building design package was being finalized and permitted. In addition, the design team worked with the VPSA manufacturer to modify the discharge silencer. The resulting design lowered the building height by 10 feet; reduced equipment, materials, construction, and operational costs; and cut the construction schedule by 2 months. The building was also hardened to meet winds from a Category 5 hurricane and rising waters from a Category 2 storm. Creative building design, extensive sound attenuating materials, and strategic vibration isolation were used to mitigate sound from the positive displacement blowers to meet all local sound ordinances and OSHA workplace criteria.

(Pictured left to right) PCL Construction team members Jean Capra, Mike Hernandez, Todd Palmatier, along with Wade Trim team members Jeff Lowe and David Mullen, received the DBIA Florida Region Merit Award for the Miami-Dade County Oxygen Production Facility on December 13.