Monson Geerts, Stephen DMcCarthy, Barbara JAxler, Richard PHenneck, Jerald2017-06-132017-06-132001-11https://hdl.handle.net/11299/188451Approximately 500,000 Minnesota residences rely on the use of onsite wastewater treatment systems and >50% of these systems may be in noncompliance with state rules or are failing to the surface. A research site at the Northeast Regional Correction Center near Duluth was established in 1995, involving~ 50 private and public sector partners, to design, construct, and monitor the performance of advanced onsite treatment systems. The systems were generally designed to treat 250 gal/day of septic tank effluent from single family homes to meet secondary treatment standards; 25 mg/L total suspended solids (TSS), 30 mg/L biochemical oxygen demand (BOD5), and 200 cfu/lOOmL fecal coliform bacteria. In 1998, pre-engineered peat filters (Puraflo®, Bord Na M6na, Inc.) were installed to compare the performance of a standard Irish peat to a Bord Na M6na specified Minnesota peat. Initially, the peat filters were operated in the recirculating mode for enhanced nitrogen removal, but were changed to single-pass mode after ponding occurred. Hydraulic failure likely resulted due to cold temperatures (since the modules were not insulated) coupled with high strength waste. With minor design modifications, including foam-insulated covers, the single-pass peat filters have operated without problems. In the recirculating mode, seasonal removal rates for both types of peat ranged 86-97% TSS, 94- 97% BOD5 96-99% fecal coliform bacteria, 6-20% total phosphorus (TP), and 31-45% total nitrogen (TN). As single-pass filters, removal rates were comparable at 89-96% TSS, 95-98% BOD5 >99% fecal coliform bacteria, 94-99% coliphages, 0-20% TP, and 24-37% TN for both peat types. The module Puraflo® peat filter systems, using both the standard Irish peat and a Minnesota peat, performed comparably and generally exceeded secondary treatment standards.enNortheast MinnesotaPeat filtersSand filtersPuraflo peat filter systemNatural Resources Research InstituteUniversity of Minnesota DuluthTechnical Report