An experiment to test nitrogen-removing septic systems in southern Hood Canal was launched Monday with the installation of a small treatment device at a home near Twanoh State Park. Environmental Earth Systems installed a commercial treatment unit designed to fi t into an existing septic tank. The unit, called RetroFAST, is manufactured by Bio-Microbics of Shawnee, Kan. It includes a blower that pumps air into one chamber of a septic tank, treating the waste aerobically, according to Ken Moody of Environmental Earth Systems.
The final stage of nitrogen removal occurs when effl uent is cycled back through another chamber of the septic tank, where anaerobic bacteria convert nitrate to nitrogen gas. Moody is looking for two other sites to retrofit under a contract with the Puget Sound Action Team.
Two other companies also contracted with the Action Team to test their systems. Terry Hull, who is supervising the project for the Action Team, said one of the key questions involves how well these denitrifying systems work in the relatively low-alkaline waters around Hood Canal, since the chemical conversion requires alkaline conditions. All the systems have been approved by the state and are in use in the region.
If it turns out that excess nitrogen is triggering Hood Canal’s low-oxygen problems, experts could propose removing nitrogen from effl uent or pumping the effl uent away from Hood Canal, Hull said. At the moment, the Action Team is not promoting these units unless someone is building a new septic system, expanding an old system or replacing a failing system. Another system being tested is a Rotating Biological Contactor (RBC) unit by Five Star Environmental of Kingston. The unit uses slowly rotating disks to aerate the waste before final nitrogen removal. Company owner Jim Patterson has selected three adjacent homes on the South Shore of Hood Canal. Each will have its own treatment unit connected to a common drainfield.
The third system is a recirculating gravel filter designed by Toby Tahja-Syrett and installed by B-Line Construction. Effluent is cycled through a sand filter an average of five times. Two homes were chosen on the North Shore of Hood Canal with one near Triton Head at the Mason-Jefferson county line. Work could begin next month, Tahja-Syrett said. Monitoring on all systems will be done by Jefferson County Health Department.