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'''A Vertical Flow Constructed Wetland is a filter bed that is planted with aquatic plants. Wastewater is poured or dosed onto the wetland surface from above using a mechanical dosing system. The water flows vertically down through the filter matrix. The important difference between a vertical and horizontal wetland is not simply the direction of the flow path, but rather the aerobic conditions.'''
Pathogen removal is accomplished by natural decay, predation by higher organisms, and sedimentation.
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{{procontable | pro=
- Does not have the mosquito problems of the [[Free-Water Surface Constructed Wetland]]. <br> - Less clogging than in a [[Horizontal Subsurface Flow Constructed Wetland|Horizontal Flow Constructed Wetland]]. <br> - Requires less space than a Free-Water Surface Constructed Wetland. <br> - High reduction in BOD, suspended solids and pathogens. <br> - Construction can provide short-term employment to local labourers. | con=
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<br>===Adequacy===
Clogging is a common problem. Therefore, the influent should be well settled with primary treatment before flowing into the wetland. This technology is not appropriate for untreated domestic wastewater (i.e. blackwater).
Vertical Flow Constructed Wetlands are best suited to warm climates but can be designed to tolerate some freezing and periods of low biological activity.
===Health Aspects/Acceptance===
The risk of mosquito breeding is low since there is no standing water. The system is generally aesthetic and can be integrated into wild areas or parklands. Care should be taken to ensure that people do not come in contact with the influent because of the risk of infection.
===Maintenance===
With time, the gravel will become clogged with accumulated solids and bacterial film. The material may have to be replaced every 8 to 15 or more years. Maintenance activities should focus on ensuring that primary treatment effectively lowers organics and solids concentrations before entering the wetland. Testing may be required to determine the suitability of locally available plants with the specific wastewater. The vertical system requires more maintenance and technical expertise than other wetland technologies.
===References===
* Crites, R. and Tchobanoglous, G. (1998). [http://books.google.com/books/about/Small_and_decentralized_wastewater_manag.html?id=yx9SAAAAMAAJ Small and Decentralized Wastewater Management Systems]. WCB and McGraw-Hill, New York, USA. pp 599–609. Comprehensive summary chapter including solved problems.
* Reed, SC. (1993). [http://water.epa.gov/type/wetlands/restore/upload/2003_07_01_wetlands_pdf_sub.pdf Subsurface Flow Constructed Wetlands For Wastewater Treatment, A Technology Assessment]. United States [http://www.epa.gov Environmental Protection Agency], USA. Comprehensive design manual.
===Acknowledgements===
{{:Acknowledgements Sanitation}}
