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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 |89]]|
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pic=Vertical_flow_constructed_wetland.png|
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Input1=Blackwater|Input2=Greywater |Input3= Brownwater | Input4= Effluent |Input5=|Output1= Effluent | Output2= Biomass | Output3= | Output4= | Output5=
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|[[Image:Vertical_flow_constructed_wetland.png |right|500px]]
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[[Image:Icon_vertical_flow_constructed_wetland.png |right|80px]]
'''A Vertical Flow Constructed Wetland vertical flow constructed wetland is a planted filter bed that is planted with aquatic plantsdrained at the bottom. Wastewater is poured or dosed onto the wetland surface from above using a mechanical dosing system. The water flows vertically down through the filter matrixto the bottom of the basin where it is collected in a drainage pipe. The important difference between a vertical and horizontal wetland is not simply the direction of the flow path, but rather the aerobic conditions.'''
<br>By intermittently dosing the wetland intermittently (four 4 to ten 10 times a day), the filter goes through stages of being saturated and unsaturated, and , accordingly, different phases of aerobic and anaerobic conditions. The frequency of dosing should be timed such that During a flush phase, the previous dose of wastewater has time to percolate percolates down through the filter unsaturated bed. As the bed so that drains, air is drawn into it and the oxygen has time to diffuse through the porous media. The filter media acts as a filter for removing solids, a fixed surface upon which bacteria can attach and a base for the vegetation. The top layer is planted and the vegetation is allowed to develop deep, wide roots, which permeate the filter media . The vegetation transfers a small amount of oxygen to the root zone so that aerobic bacteria can colonize the area and degrade organics. However, the primary role of vegetation is to maintain permeability in the filter and fill provide habitat for microorganisms. Nutrients and organic material are absorbed and degraded by the void spacesdense microbial populations. By forcing the organisms into a starvation phase between dosing phases, excessive biomass growth can be decreased and porosity increased.
===Design Considerations=== The Vertical Flow Constructed Wetland vertical flow constructed wetland can be designed as a shallow excavation or as an above ground construction. Clogging is a common problem. Therefore, the influent should be well settled in a primary treatment stage before flowing into the wetland. The design and size of the wetland is dependent on hydraulic and organic loads. Generally, a surface area of about 1 to 3 m2 per person equivalent is required. Each filter should have an impermeable liner and an effluent collection system. Vertical Flow Constructed Wetlands are most commonly designed A ventilation pipe connected to the drainage system can contribute to treat wastewater that has undergone primary treatmentaerobic conditions in the filter. Structurally, there is a layer of gravel for drainage (a minimum of 20cm20 cm), followed by layers of either sand and gravel (for settled effluent) or sand and fine gravel (for raw wastewater). 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. The top layer is planted and the vegetation is allowed to develop deep, wide roots which permeate the filter media. Depending on the climate, Phragmites australis(reed), Typha sp. (cattails ) or Echinochloa Pyramidalis pyramidalis are common plant options. The vegetation transfers a small amount of oxygen Testing may be required to determine the root zone so that aerobic bacteria can colonize the area and degrade organics. However, the primary role suitability of vegetation is to maintain permeability in the filter and provide habitat for microorganisms. During a flush phase, locally available plants with the specific wastewater percolates down through the unsaturated bed and is filtered by the sand/gravel matrix. Nutrients and organic material are absorbed and degraded by the dense microbial populations attached to the surface of the filter media and the roots. By forcing the organisms into a starvation phase between dosing phases, excessive biomass growth can be decreased and porosity increased. A drainage network at the base collects the effluent. The design and size of the wetland is dependent on hydraulic and organic loads. Pathogen removal is accomplished by natural decay, predation by higher organisms, and sedimentation.
Due to good oxygen transfer, vertical flow wetlands have the ability to nitrify, but denitrification is limited. In order to create a nitrification-denitrification treatment train, this technology can be combined with a [[Free-Water Surface Constructed Wetland|Free-Water Surface]] or [[Horizontal Subsurface Flow Constructed Wetland|Horizontal Flow Wetland]] (T.7 and T.8).
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{{procontable | pro=
- High reduction of BOD, suspended solids and pathogens <br>- Ability to nitrify due to good oxygen transfer <br>- Does not have the mosquito problems of the [[Free-Water Surface Constructed Wetland|Free-Water Surface Constructed Wetland]]. <br> - Less clogging than in a [[Horizontal Subsurface Flow Constructed Wetland|Horizontal Subsurface Flow Constructed Wetland]]. <br> - Requires less space than a Free-Water Surface Constructed or Horizontal Flow Wetland. <br> - High reduction in BODLow operating costs | con=- Requires expert design and construction, particularly, suspended solids and pathogens. the dosing system <br> - Construction can provide short-term employment to local labourers. | con=Requires more frequent maintenance than a Horizontal Subsurface Flow Constructed Wetland <br>- Constant A constant source of electrical energy may be required. <br> - Long startup time to work at full capacity <br>- Not all parts and materials may be locally available locally. <br> - Requires expert design and supervision. <br> - Moderate capital cost depending on land, liner, etc.; low operating costs. <br> - Pre-treatment is required to prevent clogging. <br> - Dosing system requires more complex engineering.
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===Appropriateness===
The vertical flow constructed wetland 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. Because of the mechanical dosing system, this technology is most appropriate where trained maintenance staff, constant power supply, and spare parts are available. Since vertical flow constructed wetlands are able to nitrify, they can be an appropriate technology in the treatment process for wastewater with high ammonium concentrations. Vertical flow constructed wetlands are best suited to warm climates, but can be designed to tolerate some freezing and periods of low biological activity.
==Adequacy=Health Aspects/Acceptance=== Clogging Pathogen removal is a common problem. Thereforeaccomplished by natural decay, 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). This is a good treatment for communities that have primary treatment (e.g. [[Septic Tank|Septic Tanks]] or [[Waste Stabilization Pond|WSPs]] but are looking to achieve a predation by higher quality effluent. This is a good option where land is cheap and available, although the wetland will require maintenance for the duration of its life. There are many complex processes at workorganisms, and accordingly, there is a significant reduction in BOD, solids and pathogensfiltration. In many cases, the effluent will be adequate for discharge without further treatment. Because of the mechanical dosing system, this technology is most appropriate for communities with trained maintenance staff, constant power supply, and spare parts. 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.
===Operation & Maintenance===
During the first growing season, it is important to remove weeds that can compete with the planted wetland vegetation. Distribution pipes should be cleaned once a year to remove sludge and biofilm that might block the holes. With time, the gravel will become clogged by accumulated solids and bacterial film. Resting intervals may restore the hydraulic conductivity of the bed. If this does not help, the accumulated material has to be removed and clogged parts of the filter material replaced. 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===
* Elizabeth Tilley etBrix, H. and Arias, C. A.al (20082005). [http://wwwocfpathplanning.eawag.chorg/organisationgraywater/abteilungen/sandec/publikationen/publications_sesp/downloads_sesp/compendium_highBrixDanishGWguidelines.pdf Compendium The Use of Vertical Flow Constructed Wetlands for on-Site Treatment of Sanitation Systems and Technologies] ([httpDomestic Wastewater://www.eawag.ch/organisation/abteilungen/sandec/publikationen/publications_sesp/downloads_sesp/compendium_low.pdf low res versionNew Danish Guidelines]). Department of Water and Sanitation in Development Countries Ecological Engineering 25 ([http5)://www.sandec.ch/ Sandec]) at the Swiss Federal Institute of Aquatic Science and Technology (Eawag). (Provides a full overview of sanitation systems491-500.)
* Crites, R. and Tchobanoglous, G. (1998). Small and Decentralized Wastewater Management Systems. WCB and /McGraw-Hill, New York, USAUS. pp 599–609. 599-609. (Book; Comprehensive summary chapter including solved problems.)
* 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.pdf Treatment Wetlands, 2nd Ed]. LondonCRC Press, Taylor & Francis Group, EarthscanBoca Raton, pp 85–187US.
* 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 IIof Municipal Wastewaters]. EPA/625/R-99/010. U.S. Environmental Protection Agency, Washington, Natural Systems for Wastewater ManagementD. Lecture NotesC. IHE Delft, The Netherlands. Chapter 6US.