Clogging in subsurface-flow treatment wetlands: occurrence and contributing factors

Paul Knowles, Gabriela Dotro*, Jaime Nivala, Joan García

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Clogging is a major operational and maintenance issue associated with the use of subsurface flow wetlands for wastewater treatment, and can ultimately limit the lifetime of the system. This review considers over two decades of accumulated knowledge regarding clogging in both vertical and horizontal subsurface flow treatment wetlands. The various physical, chemical and biological factors responsible for clogging are identified and discussed. The occurrence of clogging is placed into the context of various design and operational parameters such as wastewater characteristics, upstream treatment processes, intermittent or continuous operation, influent distribution, and media type. This information is then used to describe how clogging develops within, and subsequently impacts, common variants of subsurface flow treatment wetland typically used in the U.S., U.K., France and Germany. Comparison of these systems emphasized that both hydraulic loading rate and solids loading rate need to be considered when designing systems to operate robustly, i.e. hydraulic overloading makes horizontal-flow tertiary treatment systems in the U.K. more susceptible to clogging problems than vertical-flow primary treatment systems in France. Future research should focus on elucidating the underlying mechanisms of clogging as they relate to the design, operation, and maintenance of subsurface flow treatment wetlands.

Original languageEnglish
Pages (from-to)99-112
Number of pages14
JournalEcological Engineering
Issue number2
Early online date23 Aug 2010
Publication statusPublished - Feb 2011


  • clog matter
  • constructed wetland
  • design
  • horizontal flow
  • loading rates
  • review
  • vertical flow


Dive into the research topics of 'Clogging in subsurface-flow treatment wetlands: occurrence and contributing factors'. Together they form a unique fingerprint.

Cite this