The utilities division of Spokane County, in Washington, built an advanced wastewater treatment plant called the Spokane County Regional Water Reclamation Facility.
The plant is constructed on a site located in the eastern industrial area of the city of Spokane. Generally, the Spokane Valley, east of the city, is served by the new facility.
The $173m project commenced in June 2009 and entered service in December 2011, ahead of schedule. The initial daily treatment capacity is eight million gallons a day (mgd). It can, however, be increased in phases to 24mgd.
Purpose of the programme to eliminate the use of septic tanks
The wastewater produced in the Spokane Valley service area was sent to the Riverside Park Water Reclamation Facility. A programme was started in 1980 to eliminate the use of septic tanks by connecting its customers to the sewer system.
More than 80,000 customers were provided connections to the sewer system by 2006 and it is expected 9,000 more will be added by 2014. The population served by the sewer system is projected to reach 167,000 by 2026.
Projected population growth and the septic tank removal programme will lead to substantial increases in wastewater flow. The new water reclamation facility was planned, beginning in 1999, because the Riverside Park Water Reclamation Facility does not have the capacity to treat the increased wastewater flow.
The new plant enhances the county’s wastewater treatment capability and serves the projected population growth. It also improves the water quality in the region and reduces the phosphorus discharges to the Spokane River.
Facilities in Spokane County’s new water reclamation complex
The facility comprises three non-process buildings including a 5,150 square feet water resource centre, an 8,050 square feet treatment operations facility and a maintenance building.
The water resource centre, which includes a classroom and display room, is intended to be used for educational purposes. The treatment operations building includes offices and a laboratory for the water reclamation facility.
The treatment unit makes use of nitrification / de-nitrification membrane bioreactor (MBR) technology. It has facilities for fine screening and primary clarification.
It also has grit removal, anaerobic and aerobic digestion and chemical feed systems. Disinfection is achieved by using sodium hypochlorite solution.
Primary and waste activated sludge will be thickened using gravity belts. Final dewatering will use centrifuges.
Construction of the Washington-based advanced wastewater treatment plant
Construction of the reclamation facility commenced in June 2009. The clearing and grading activities and under-slab piping were completed in fall 2009.
Exterior construction of the buildings, water resource centre and treatment operations facility was completed in spring 2010. Construction of the building interiors, roof of the aeration basins, foundations and walls of the primary clarifiers were completed in summer 2010.
Work within the maintenance building was substantially completed by spring 2011. Electrical ductbanks were also installed during this period. Installation of system control and data acquisition (SCADA) systems commenced in spring 2011.
Technology used at the Spokane County regional water reclamation facility
The Spokane County Regional Water Reclamation Facility is equipped with GE Water Technologies’ membrane bioreactor (MBR) to treat the wastewater.
The MBR is allowed for high solids removal and used water filtration. The MBR plant uses immersed hollow-fibre membranes to remove particles from the wastewater.
MBR plants produce less residual waste in comparison with conventional water treatment systems. They also use fewer chemicals and require less land.
Key players and contractors involved in the Spokane Valley facility
The Spokane County owns the plant and also financed the project. A Design, Build and Operate (DBO) contract worth $260m was awarded to CH2M Hill Constructors in January 2009.
CH2M Hill will operate the plant for 20 years under the DBO contract. It is also responsible for on-site bio-solids treatment.
Local general contractor / construction manager, Garco Construction, was the main subcontractor. Halme Construction was subcontracted to perform earthwork and yard piping.
Most of the pipe and fittings used by Halme have been supplied by HD Fowler and U.S. Pipe.
Other subcontractors included Power City Electric, University Mechanical and GE Water Technologies. CH2M Hill hired 56 local subcontractors for the construction.