<!{|style="float: left;"|{{Language-box|english_link=Horizontal_Subsurface_Flow_Constructed_Wetland|french_link=Filtre_planté_à_écoulement_horizontal_sous- table at top of page with logo, picture, Application level, Management level, and input-output tables -->surface|spanish_link=Humedal_Artificial_de_Flujo_de_Horizontal_subsuperficial|hindi_link=coming soon|malayalam_link=coming soon|tamil_link=coming soon | korean_link=coming soon | chinese_link=Coming soon | indonesian_link=Coming soon | japanese_link=Coming soon}}|}{|width="100%"|style="width:50%;"|{{santablesantable_new|
sys1=[[Single Pit System |1]]|
sys2=[[Blackwater Treatment System with Infiltration|56]]|sys3=[[Blackwater Treatment System with SewerageEffluent Transport|67]]|sys4=[[Blackwater Transport to (Semi-) Centralized Treatment System |78]]|sys5=[[Sewerage System with Urine Diversion|9]]|
sys6=|
sys7=|
sys8=|
sys9=|
pic=Horizontal_subsurface_flow_consructed_wetland.png|
ApplHousehold=X|
ManShared=XX|
ManPublic=XX|
Input1=Blackwater|Input2=Greywater |Input3= Brownwater | Input4= Effluent |Input5=|Output1= Effluent | Output2= Biomass | Output3= | Output4= | Output5=
}}
|[[Image:Horizontal_subsurface_flow_consructed_wetland.png |right|500px]]
|}
<br>
----
<br>
[[Image:Icon_horizontal_subsurface_flow_constructed_wetland.png |right|95px80px]]'''A Horizontal Subsurface Flow Constructed Wetland horizontal subsurface flow constructed wetland is a large gravel and sand-filled channel basin that is planted with aquatic wetland vegetation. As wastewater flows horizontally through the channelbasin, the filtermaterial filter material filters out particles and microorganisms degrade the organics.'''
<br>The water level in filter media acts as a filter for removing solids, a fixed surface upon which bacteria can attach, and a Horizontal Subsurface Flow Constructed Wetland is maintained at 5 to 15cm below base for the surface to ensure subsurface flowvegetation. The bed should be wide Although facultative and shallow so that anaerobic bacteria degrade most organics, the flow path vegetation transfers a small amount of oxygen to the water is maximized. A wide inlet root zone should be used to evenly distribute so that aerobic bacteria can colonize the flowarea and degrade organics as well. Pre-treatment is essential to prevent clogging and ensure efficient treatmentThe plant roots play an important role in maintaining the permeability of the filter.
===Design Considerations=== The design of a horizontal subsurface flow constructed wetland depends on the treatment target and the amount and quality of the influent. It includes decisions about the amount of parallel flow paths and compartmentation. The removal efficiency of the wetland is a function of the surface area (length multiplied by width), while the cross-sectional area (width multiplied by depth) determines the maximum possible flow. Generally, a surface area ofabout 5 to 10 m2 per person equivalent is required. Pre- and primary treatment is essential to prevent cloggingand ensure efficient treatment. The influent can be aerated by an inlet cascade to support oxygen-dependentprocesses, such as BOD reduction and nitrification. The bed should be lined with an impermeable liner (clay or geotextile) to prevent leaching. Small, round, evenly sized gravel (3–32mm It should be wide and shallow so that the flow path of the water in diameter) contact with vegetation roots is most commonly maximized. A wide inlet zone should be used to fill evenly distribute the bed to a depth of 0flow.5 A well-designed inlet that allows for even distribution is important to 1mprevent short-circuiting. To limit clogging, The outlet should be variable so that the gravel should water surface can be clean and free of fines. Sand is also acceptable, but is more prone adjusted to clogging. In recent years, alternative filter materials such as PET have been successfully usedoptimize treatment performance.
The removal efficiency of the wetland is a function of the surface area Small, round, evenly sized gravel (length multiplied by width3 to 32 mm in diameter), while is most commonly used to fill the cross-sectional area (width multiplied by bed to a depth) determines the maximum possible flowof 0. A well-designed inlet that allows for even distribution is important 5 to prevent short-circuiting1 m. The outlet To limit clogging, the gravel should be variable so that the water surface can be adjusted clean and free of fines. Sand is also acceptable, but is more prone to optimize treatment performanceclogging than gravel. The In recent years, alternative filter media acts materials, such as both a filter for removing solidsPET, a fixed surface upon which bacteria can attach, and a base for the vegetation. Although facultative and anaerobic bacteria degrade most organics, the vegetation transfers a small amount of oxygen to the root zone so that aerobic bacteria can colonize the area and degrade organics as wellhave been successfully used. The plant roots play an important role water level in maintaining the permeability of wetland is maintained at 5 to 15 cm below the filtersurface to ensure subsurface flow. Any native plant with deep, wide roots that can grow in the wet, nutrient-rich environment is appropriate. Phragmites australis (reed) is a common choice because it forms horizontal rhizomes that penetrate the entire filter depth. Pathogen removal is accomplished by natural decay, predation by higher organisms, and sedimentation.
<br>
{{procontable | pro=
- Requires less space than a Free-Water Surface Constructed Wetland. <br> - High reduction in of BOD, suspended solids and pathogens. <br> - Does not have the mosquito problems of the [[<br>- Free-Water Surface Constructed Wetland]]. <br> - Can be built and repaired with locally available materials. No electrical energy is required <br> - Construction can provide shortLow operating costs| con=-term employment to local labourers. Requires a large land area <br> - No electrical energy required. | con=- Requires expert design and supervision. Little nutrient removal <br> - Moderate capital cost Risk of clogging, depending on land, liner, fill, etc.; low operating costs. pre- and primary treatment <br>- PreLong startup time to work at full capacity <br>-treatment is required to prevent clogging.Requires expert design and construction
}}
==Adequacy=Appropriateness=== Clogging is a common problem and, 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). It is a good treatment for communities that have primary treatment (e.g., [[Septic Tank|Septic Tanks]], S.9), but are looking to achieve a higher quality effluent.
Clogging The horizontal subsurface flow constructed wetland is a common problem good option where land is cheap and therefore available. Dependingon the influent should be well settled with primary treatment before flowing into volume of the water and the corresponding area requirement of the wetland. This technology is not , it can be appropriate for untreated domestic waste water (ismall sections of urban areas, as well as for peri-urban and rural communities.e. blackwater)It can also be designed for single households. This technology is a good treatment best suited for communities that have primary treatment (e.g. [[Septic Tank|Septic Tanks]] or [[Waste Stabilization Pond|WSPs]]) warm climates, but are looking it can be designed to achieve a higher quality tolerate some freezing and periods of low biological activity. If the effluent. This is to be reused, the losses due to high evapotranspiration rates could be a good option where land is cheap and availabledrawback of this technology, although the wetland will require maintenance for depending on the duration of its lifeclimate.
Depending on ===Health Aspects/Acceptance=== Significant pathogen removal is accomplished by natural decay, predation by higher organisms, and filtration. As the volume of water, and therefore flows below the sizesurface, this type any contact of wetland can be appropriate for small sections pathogenic organisms with humans and wildlife is minimized. The risk of urban areas, perimosquito breeding is reduced since there is no standing water compared to the risk associated with [[Free-Water Surface Constructed Wetland|Free-urban Water Surface Constructed Wetlands]] (T.7). The wetland is aesthetically pleasing and rural communities. They can also be designed for single householdsintegrated into wild areas or parklands.
Horizontal Subsurface Flow Constructed Wetlands are best suited for warm climates but they ===Operation & Maintenance=== During the first growing season, it is important to remove weeds that can be designed to tolerate some freezing compete with the planted wetland vegetation. With time, the gravel will become clogged with accumulated solids and periods bacterial film. The filter material at the inlet zone will require replacement every 10 or more years. Maintenance activities should focus on ensuring that primary treatment is effective at reducing the concentration of low biological activitysolids in the wastewater before it enters the wetland. Maintenance should also ensure that trees do not grow in the area as the roots can harm the liner.
==Health Aspects/Acceptance=References======References===* Crites, R. and Tchobanoglous, G. (1998). Small and Decentralized Wastewater Management Systems. WCB/McGraw- Hill, New York, US. pp. 599-609. (Book; Comprehensive summary chapter including solved problems)
The risk of mosquito breeding is reduced since there is no standing water compared to the risk associated with * Hoffmann, H., Platzer, C., Winker, M. and von Münch, E. (2011). [[Freehttps://www.susana.org/en/knowledge-hub/resources-and-Water Surface publications/library/details/930 Technology Review of Constructed Wetland|Free-Water Surface Wetlands. Subsurface Flow Constructed Wetlands]for Greywater and Domestic Wastewater Treatment]. The wetland is aesthetically pleasing and can be integrated into wild areas or parklandsGesellschaft für Internationale Zusammenarbeit (GIZ) GmbH, Eschborn, DE.
==Maintenance==* Kadlec, R. H. and Wallace, S. D. (2009). [https://sswm.info/sites/default/files/reference_attachments/KADLEC%20WALLACE%202009%20Treatment%20Wetlands%202nd%20Edition_0.pdf Treatment Wetlands, 2nd Ed]. CRC Press, Taylor & Francis Group, Boca Raton, US.
With time, the gravel will clog with accumulated solids and bacterial film* UN-HABITAT (2008). [https://unhabitat. The filter material will require replacement every 8 to 15 or more yearsorg/constructed-wetlands-manual Constructed Wetlands Manual]. Maintenance activities should focus on ensuring that primary treatment is effective at reducing the concentration of solids in the wastewater before it enters the wetlandUN-HABITAT Water for Asian Cities Programme. Maintenance should also ensure that trees do not grow in the area as the roots can harm the linerKathmandu, NP.
* U.S. EPA (2000). [https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=64144&Lab=NRMRL Constructed Wetlands Treatment of Municipal Wastewaters]. EPA/625/R-99/010. U.S. Environmental Protection Agency, Washington, D.C., US. ===Acknowledgements===
{{:Acknowledgements Sanitation}}
==References and external links==
* Crites, R. and Tchobanoglous, G. (1998). Small and Decentralized Wastewater Management Systems. WCB and McGraw-Hill, New York, USA. pp 599–609. (Comprehensive summary chapter including solved problems.)
* Mara, DD. (2003). Domestic wastewater treatment in developing countries. Earthscan, London. pp 85–187.
* Poh-Eng, L. and Polprasert, C. (1998). Constructed Wetlands for Wastewater Treatment and Resource Recovery. Environmental Sanitation Information Center, AIT, Bangkok, Thailand.
* Polprasert, C., et al. (2001). Wastewater Treatment II, Natural Systems for Wastewater Management. Lectur Notes, IHE Delft, The Netherlands. Chapter 6.
* Reed, SC. (1993). Subsurface Flow Constructed Wetlands For Wastewater Treatment, A Technology Assessment. United States Environmental Protection Agency, USA. Available: http://www.epa.gov (Comprehensive design manual.)