Residential subsurface flow treatment wetlands in northern Minnesota

R. Axler, J. Henneck, B. McCarthy

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Approximately 30% of Minnesotans use on-site systems (∼500,000 residences) and >50% are failing or non-compliant with regulations due to restrictive soils and site conditions. Many sites occur near lakes and streams creating health hazards and deteriorating water quality. SSF CWs have been evaluated year-round at two northern sites since 1995. The NERCC CWs simulate single homes and the Grand Lake demonstration CW treats STE from a cluster of 9 lakeshore homes. Systems were generally able to achieve design criteria of 25 mg TSS/L and 30 mgBOD5/L and the NERCC CWs required only 0.3m of unsaturated soil to achieve consistent disinfection to <200 fecals/100 mL year round. Seeding experiments with Salmonella indicated removal efficiencies of 99.8% in summer and 95% in winter. High strength (∼300 mgBOD/L, 95 mg TN/L) influent at NERCC probably limited system performance, particularly N-removal (mass) which was ∼42% in summer and 20% in winter. The data indicate CW's are a viable, year-round treatment option for homeowners in terms of performance, ease of operation, and cost but require additional maintenance related to inconsistent vegetation growth, winter insulation, and meeting concentration-based regulatory standards since they were seasonally and annually variable due to rain events, partial freezing, spring snowmelt, and summer evapotranspiration.

Original languageEnglish (US)
Pages (from-to)345-352
Number of pages8
JournalWater Science and Technology
Issue number11-12
StatePublished - 2001


  • Alternative technologies
  • Cold-climate
  • Constructed wetlands
  • Pathogens
  • Wastewater


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