City of Airway Heights Water Reclamation Plant Project, United States of America
Key Data
The city of Airway Heights is working on a water reclamation project, which is one of the most substantial developments in the city's history.
The $44m Airway Heights Water Reclamation project involves construction of a wastewater treatment plant and a new reuse water distribution system. The plant is one of the most advanced wastewater treatment plants in the region.
The initial treatment capacity of the plant is one million gallons a day (mgd). A future expansion will increase the plant's capacity to 1.5mgd, covering the city's needs for the next 20 years.
Ground for the plant was broken in May 2009 and the plant was commissioned in November 2011. Construction is being carried out in two phases. Phase one is comprised of two sub-phases: phase 1A and phase 1B.
Phase two is a planned future project that will increase the treatment capacity to 1.5mgd.
Purpose of the Airway Heights Water Reclamation Plant
The city's sewer flow was being discharged to the city of Spokane-owned wastewater system through the West Plains Interceptor. Under an interlocal agreement, Airway Heights can discharge only 1mgd of sewage through the Spokane system.
As the city is projected to reach the maximum levels soon, it was decided it needed to build a water reclamation facility of its own.
The plant allows the city to meet future sewer service and water service demands. It contributes to the conservation of the city's existing potable water supply by pumping the reclaimed water into the aquifer. The plant eliminates the discharge of wastewater into the Spokane River.
Project background
The decision to build the reclamation plant was taken by the Wastewater Steering Committee after a series of studies conducted between 2003 and 2005. The design of the reclamation plant was completed in late 2007 and funds were secured in early 2009.
Water reclamation plant facilities
The plant has anoxic and anaerobic basins in a single structure separated by a wall. The aeration basins are of bubbler type technology which divides the basins into two cells. The rectangular basins reduce the size of the emergency storage lagoon.
The plant includes an equipment corridor between the two basins, a utility corridor and an influent pump station.
Treatment of wastewater
The plant treats the sewage to class A recycled water fit for human contact, but unfit for drinking, bathing or swimming. It produces 500,000 gallons a day.
The plant has an aeration activated sludge system that removes biological nitrogen and phosphorus. The treatment process involves advanced biological treatment, coagulation and additional disinfection.
Membrane filtration during the final stage of treatment gives class A standard to the water. Groundwater quality is protected by removing nitrogen from the water.
The reclaimed water is used for commercial and industrial uses, aquifer recharge and irrigation.
Financing the city of Airways Heights project
Phase 1A of the project cost $11m and phase 1B $33m. Funds for phase 1A were secured from the Ecology Centennial Clean Water Fund ($2.9m), Washington State Public Works Trust Fund Loan ($7m) and city of Airway Heights Capital Program matching funds ($1m).
Phase 1B obtained $2m from the Ecology Centennial Clean Water Fund and $22m from the Department of Ecology. The shortfall in the funding of phase 1B is funded through sewer rate collections.
Plant construction and key players involved
The plant was designed by the Spokane-based Century West Engineering Corporation. It also prepared environmental documentation and obtained permits for the project.
Robert B Goebel General Contractor was contracted to undertake phase 1A of the project for $7.3m.
Phase 1A included construction of a two million gallon reclaimed-water storage tower, administrative buildings, an anaerobic process basin, tanks and sewer lines.
Phase 1B was undertaken by IMCO General Construction under a $27m contract. The scope of work included construction of the final treatment building, a RAS/WAS pumping building, a new headworks building, dewatering building, a temporary covered storage lagoon, an influent pump station and a storage tank.
