The Navajo Tribal Utility Authority has agreed to bring six wastewater treatment facilities into compliance with the federal and Navajo laws in...
The Washington State Fire Training Academy (FTA) is owned and operated by the Washington State Patrol. It serves fire agencies throughout the state, both public and private, and from other states and overseas. The Air Rescue Firefighting facility is particularly popular because it is one of only a few in the world that meets all requirements for providing FAA airport A-BC-DC certification and the Trans-Canada Aeronautic Airfield Requirements. The FTA, however, has water rights for only 12 acre/ft per year, or an average of about 10,700 gal per day (gpd)—a small quantity for fire training. It is really only sufficient to provide potable water for drinking, showers, laundry and similar domestic uses.
Water for fire training previously was provided by recycling water runoff from fire training and making up water lost to steam from captured onsite storm water. During dry periods, fire training had to be curtailed due to lack of water. Population growth and increased economic activity have resulted in increased fire protection demands, which required additional training. A reliable source of added water was needed to permit year-round fire training.
The FTA is located on a remote 51-acre site about 35 miles east of Seattle and one mile north of I-90 in the foothills of the Cascade Mountains at an elevation of about 1,550 ft.
Membrane bioreactor (MBR) technology with disinfection has been proven over the years to produce Class A reclaimed water, per Washington Department of Health standards. The innovative aspects for the FTA are the features incorporated in the MBR facility that make reclaiming wastewater for fire training economically practical and feasible.
In the past, very small, remote wastewater treatment facilities have been impractical because of the costs incurred for a surface water discharge permit and the requirements for daily operation, effluent monitoring and testing. The resulting total operating costs could not be supported by the small number of users.
The FTA project demonstrates that small remote wastewater treatment facilities are practical to reclaim water for various uses with current technology. Simple “packaged” equipment designed on skids reduces capital costs because these units are fully assembled and tested at the factory before shipment to the construction site. Continuous reading and recording of key operating parameters, including trans-membrane pressure, effluent turbidity, ultraviolet (UV) light disinfection intensity and chlorine residual, allow for remote operation using a laptop computer from anywhere with Internet access.
Reliability and redundancy are provided through one-day emergency storage provisions with automatic flow diversion. Influent flow equalization and the ability to produce reclaimed water in batches eliminated daily water quality testing requirements on non-discharge days. Remote contract operation allows several reclaimed water plants to be managed simultaneously by a single certified operator.
None of the fire training water passes through the MBR facility. Instead, the MBR reclaims domestic wastewater to supplement the existing training water supply and allow fire training even during dry periods with little rain. The domestic sewage has an influent five-day biochemical oxygen demand and total suspended solids concentration of 200 to 350 mg/L. The total influent nitrogen concentration is 40 to 70 mg/L. Current average daily flows of less than 10,000 gpd are projected to approach 25,000 gpd within 20 years as fire training intensifies. Class A reclaimed water requires coagulation, filtration and disinfection to less than 2.2 total coliforms per 100 mL.
The 25,000-gpd design flow for the FTA is of similar magnitude to that of a residential community of about 100 homes. The final construction cost was about $2 million, including about 1,500 ft of 8-in. gravity sewers. This cost of about $20,000 per equivalent single-family residence makes wastewater treatment affordable even for very small communities because the cost of an onsite aerobic system is similar but the effluent quality is not as reliable.
While treatment is not the entire cost for a complete sewer system, it is usually the largest component. The reclaimed water is reusable for irrigation, dual plumbing systems or industrial applications such as fire fighting. Disposal of any surplus reclaimed water is simpler, as surface percolation does not require a National Pollution Discharge Elimination System permit.
The FTA design incorporated extensive monitoring with a SCADA system to facilitate remote operation of the facility. At present, the FTA is one of several systems managed by a contract operator located in Shelton, Wash., more than 70 miles away. The operator monitors the facility daily but only visits the FTA site twice weekly, at an annual cost of $50,000. This annual operating cost is equivalent to approximately $42 a month per home.