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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=|
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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=
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|[[Image:Horizontal_subsurface_flow_consructed_wetland.png |right|500px]]
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[[Image:Icon_horizontal_subsurface_flow_constructed_wetland.png |right|80px]]
'''A horizontal subsurface flow constructed wetland is a large gravel and sand-filled basin that is planted with wetland vegetation. As wastewater flows horizontally through the basin, the filter material filters out particles and microorganisms degrade the organics.'''
===Design Considerations=== The water level in design of a Horizontal Subsurface Flow Constructed Wetland is maintained at 5 to 15cm below the surface to ensure horizontal subsurface flowconstructed wetland depends on the treatment target and the amount and quality of the influent. The bed should be wide and shallow so that It includes decisions about the amount of parallel flow path paths and compartmentation. The removal efficiency of the water wetland is maximizeda function of the surface area (length multiplied by width), while the cross-sectional area (width multiplied by depth) determines the maximum possible flow. A wide inlet zone should be used Generally, a surface area ofabout 5 to evenly distribute the flow10 m2 per person equivalent is required. Pre-and primary treatment is essential to prevent clogging and ensure efficient treatment.The influent can be aerated by an inlet cascade to support oxygen-dependent processes, 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 in diameter) is most commonly used to fill the bed to a depth of 0.5 to 1m. To limit clogging, the gravel It should be clean wide and free shallow so that the flow path of fines. Sand the water in contact with vegetation roots is also acceptable, but is more prone to cloggingmaximized. In recent years, alternative filter materials such as PET have been successfully A wide inlet zone should be used. The removal efficiency of the wetland is a function of to evenly distribute the surface area (length multiplied by width), while the cross-sectional area (width multiplied by depth) determines the maximum possible flow. A well-designed inlet that allows for even distribution is important to prevent short-circuiting. The outlet should be variable so that the water surface can be adjusted to optimize treatment performance. The filter media acts as both a filter for removing solids, 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 well. The plant roots play an important role in maintaining the permeability of the filter. Any 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.
Small, round, evenly sized gravel (3 to 32 mm in diameter) is most commonly used to fill the bed to a depth of 0.5 to 1 m. To limit clogging, the gravel should be clean and free of fines. Sand is also acceptable, but is more prone to clogging than gravel. In recent years, alternative filter materials, such as PET, have been successfully used. The water level in the wetland is maintained at 5 to 15 cm below the surface 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.
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===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.
===Health Aspects/Acceptance===
Significant pathogen removal is accomplished by natural decay, predation by higher organisms, and filtration. As the water flows below the surface, any contact of pathogenic organisms with humans and wildlife is minimized. The risk of mosquito breeding is reduced since there is no standing water compared to the risk associated with [[Free-Water Surface Constructed Wetland|Free-Water Surface Constructed Wetlands]] (T.7). The wetland is aesthetically pleasing and can be integrated into wild areas or parklands.
==References=Operation & Maintenance=== During the first growing season, it is important to remove weeds that can compete with the planted wetland vegetation. With time, the gravel will become clogged with accumulated solids and 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 solids 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.
===References======References===* Elizabeth Tilley etCrites, R. and Tchobanoglous, G.al (20081998). [http://www.eawag.ch/organisation/abteilungen/sandec/publikationen/publications_sesp/downloads_sesp/compendium_high.pdf Compendium of Sanitation Small and Decentralized Wastewater Management Systems and Technologies] ([http://www.eawag.chWCB/organisation/abteilungen/sandec/publikationen/publications_sesp/downloads_sesp/compendium_lowMcGraw- Hill, New York, US.pdf low res version])pp. Department of Water and Sanitation in Development Countries ([http://www599-609.sandec.ch/ Sandec]) at the Swiss Federal Institute of Aquatic Science and Technology (Eawag). (Provides a full overview of sanitation systems.Book; Comprehensive summary chapter including solved problems)
* CritesHoffmann, RH., Platzer, C., Winker, M. and Tchobanoglousvon Münch, GE. (19982011). Small and Decentralized Wastewater Management Systems[https://www.susana. WCB org/en/knowledge-hub/resources-and McGraw-Hill, New York, USApublications/library/details/930 Technology Review of Constructed Wetlands. pp 599–609Subsurface Flow Constructed Wetlands for Greywater and Domestic Wastewater Treatment]. Gesellschaft für Internationale Zusammenarbeit (Comprehensive summary chapter including solved problemsGIZ) GmbH, Eschborn, DE.)
* MaraKadlec, DDR. H. and Wallace, S. D. (20032009). Domestic wastewater treatment in developing countries[https://sswm.info/sites/default/files/reference_attachments/KADLEC%20WALLACE%202009%20Treatment%20Wetlands%202nd%20Edition_0. Earthscanpdf Treatment Wetlands, London2nd Ed]. pp 85–187CRC Press, Taylor & Francis Group, Boca Raton, US.
* PohUN-Eng, L. and Polprasert, C. HABITAT (19982008). [https://unhabitat.org/constructed-wetlands-manual Constructed Wetlands Manual]. UN-HABITAT Water for Wastewater Treatment and Resource RecoveryAsian Cities Programme. Environmental Sanitation Information Center, AIT, BangkokKathmandu, ThailandNP.
* Polprasert, CU., et alS. EPA (20012000). Wastewater [https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=64144&Lab=NRMRL Constructed Wetlands Treatment II, Natural Systems for Wastewater Managementof Municipal Wastewaters]. EPA/625/R-99/010. U.S. Lectur NotesEnvironmental Protection Agency, IHE DelftWashington, The NetherlandsD.C. Chapter 6, US.