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Reed beds are a natural habitat that is found in floodplains, waterlogged depressions and estuaries. Reed beds are part of a succession from young reed colonising open water or wet ground through a graduation of increasingly dry ground. As reed beds age, they build up a considerable litter layer which eventually rises above the water level, and ultimately provides opportunities for scrub or woodland invasion.

Most European reed beds are composed mainly of common reed (Phragmites australis), but also include other tall monocotyledons adapted to growing in water, including sedges (species of Carex, Scirpus Schoenoplectus and related genera).

Reed beds vary in the species they can support, depending on water levels within the wetland system, and the nutrient status and salinity of the water. Those that normally have 20 cm or more of surface water during the summer are referred to as ‘reed swamp’. These often have high invertebrate and bird species use. Reed beds with water levels at or below the surface during the summer are often more complex botanically and are known as ‘reed fen’.

Although common reed is characteristic of reed beds, not all vegetation dominated by this species is reed bed. It also commonly occurs in damp grassland which is unmanaged, and as an understorey in certain types of damp woodland.

Constructed wetlands

Constructed wetlands are artificial reed beds (sometimes called reed fields) which are used as a part of small-scale sewage treatment systems: water trickling through the reed bed is cleaned by the root system and its associated microorganisms utilising the sewage for growth nutrients, resulting in a clean effluent. The process is very similar to the normal aerobic conventional sewage treatment, as the same organisms are used, except that conventional treatment systems (often using an activated sludge process) require artificial aeration.

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 {{Copyedit|date=October 2007}}
 [[Image:Phragmites australis1.jpg|thumb|300px|A reed bed in summer]]
-'''Reed beds''' are a natural habitat that are found in [[floodplain]]s, waterlogged depressions and [[estuary|estuaries]]. Reed beds are part of a [[succession]] from young reed colonising open water or wet ground through a gradation of increasingly dry ground. As reed beds age, they build up a considerable litter layer which eventually rises above ground or water level, and ultimately provides opportunities for [[scrubland|scrub]] or woodland invasion.
+'''Reed beds''' are a natural habitat that is found in [[floodplain]]s, waterlogged depressions and [[estuary|estuaries]]. Reed beds are part of a [[succession]] from young reed colonising open water or wet ground through a graduation of increasingly dry ground. As reed beds age, they build up a considerable litter layer which eventually rises above the water level, and ultimately provides opportunities for [[scrubland|scrub]] or woodland invasion.
+Most European reed beds are composed mainly of common reed (''[[Phragmites australis]]''), but also include other tall [[monocotyledons]] adapted to growing in water, including sedges ([[species]] of ''[[Carex]]'', ''[[Scirpus]]'' ''[[Schoenoplectus]]'' and related [[Genus|genera]]).
-Most European reed bed [[species]] incorporated in [[genus|genera]] ''[[Phragmites]]'' and ''[[Scirpus]]''.
-Reed beds vary in the species they can support, depending on water levels within the wetland system. Those that normally have 20 cm or more of surface water during the summer are referred to as ‘reed swamp’. These often have high invertebrate and bird species use. Reed beds with water levels at or below the surface during the summer are often more complex botanically and are known as ‘reed fen’.
+Reed beds vary in the species they can support, depending on water levels within the wetland system, and the nutrient status and salinity of the water. Those that normally have 20 cm or more of surface water during the summer are referred to as ‘reed swamp’. These often have high invertebrate and bird species use. Reed beds with water levels at or below the surface during the summer are often more complex botanically and are known as ‘reed fen’.
+Although common reed is characteristic of reed beds, not all vegetation dominated by this species is reed bed.  It also commonly occurs in damp [[grassland]] which is unmanaged, and as an [[understorey]] in certain types of damp [[woodland]].
-[[Image:Reedbeach edit1.JPG|thumb|left|600 px| A previously sandy beach invaded by reeds forming a reed bed.]]
+[[Image:Reedbeach edit1.JPG|thumb|right|600 px| A previously sandy beach invaded by reeds forming a reed bed.]]
-==Sewage treatment==
+==Constructed wetlands==
-[[Constructed wetland]]s are artificial reed beds (sometimes called "reed fields") which are used as a part of small-scale [[sewage]] treatment systems: [[water]] trickling through the reed bed is cleaned by the root system and its associated [[microorganism]]s utilising the sewage for growth [[nutrient]]s, resulting in a clean [[effluent]]. The process is very similar to the normal aerobic conventional sewage treatment as the same organisms are used here too, except that conventional treatment system (often an activated sludge process) requires artificial aeration.
+{{Main article|Constructed wetlands}}
+[[Constructed wetland]]s are artificial reed beds (sometimes called ''reed fields'') which are used as a part of small-scale [[sewage]] treatment systems: [[water]] trickling through the reed bed is cleaned by the root system and its associated [[microorganism]]s utilising the sewage for growth [[nutrient]]s, resulting in a clean [[effluent]]. The process is very similar to the normal aerobic conventional sewage treatment, as the same organisms are used, except that conventional treatment systems (often using an activated sludge process) require artificial aeration.
-The reed bed sewage treatment systems does not require any power, chemical, manpower to operate and is generally do not need any maintenance/monitoring and often produces better quality water than the well operated conventional treatment systems. The flop side of the technology is that it consumes much more area than the conventional systems - almost 5 times. But with intelligent planning, the initial tanks can be constructed underground and the rootzone systems can be developed as a green belt and even as a garden.
-Slowly, but surely, people are thinking in this line. The recently commissioned sewage reclamation system in Madras Club, Chennai, India is a case in point. The Club saves two tanker loads of water every day by recovering clean water from sewage using the treatment plant and use it for gardening. The picture attached shows the plant. The Chennai based Indo-German Company Schemco Consult Private Ltd (SCPL) was responsible for the design and commissioning of the system.
-The plant consists of a collection tank, hybrid anaerobic digestor and reed beds and occupies approximately 300 m2 area for a treatment capacity of 25000 litres per day. The reeds grown are Phragmites Australlis, a special reed capable of providing the best treatment among the wetland plants.
-Another case is of Aravind Eye Hospital, Pondicherry and none of the visitors to the Hospital for the last 18 months ever suspected that the beautiful garden they are passing through is in fact a waste water treatment plant! The hospital uses the recovered water for washings, irrigation etc., which on one hand reduced the water requirement for the hospital and on the other, solved the problem of sewage treatment and disposal. BORDA, Germany provided technical assistance to this project.
-Unfortunately, designing something simple to operate is not simple at all and the rootzone systems are no exception. The effectiveness of the system depends much on the efficacy of distribution mechanism and the design and construction need the services of an experienced hydraulic engineer.
-There are vertical and horizontal flow reed beds. While the efficiency of the vertical flow systems are higher than the other, it is more prone to clogging and hence most tropical installations (where the bacterial growth can be quite intense due to favourable temperature), a horizontal flow installation is preferred.
-'''Design'''
-Vertical reed beds could be planned with an area requirement of  2 m²/PE (Population Equivalents). Horizontal reed beds could be planned with an area requirement of  4   m²/PE.  Population Equivalents are most commonly expressed in terms of BOD5. An average value of 0.077 kg, 5-day, 20°C BOD per person per day is used for determination of the PE.
-For design of reed bed, it is assumed that the oxygen supply to the rootzone is 40 g/m2 and normal BOD loading rates to the CWL is 15-40 g BOD/m2/d
-Reaction rates
-r<sub>T</sub> = -k<sub>d</sub> x X
-rT = 	reaction rate at T °C
-kd depends on the Temperature.
-r<sub>T</sub> = r <sub>20</sub> x θ<sup> (T-20) </sup>
-rT = 	reaction rate at T °C
-r20 = 	reaction rate at 20 °C
-θ = 	Temperature coefficient
-T = 	Temperature [°C]
-Typical values for θ scan be found in the following table.
-Process                       Range               Average
-Activated Sludge              1,00 - 1,04        1,04
-Aerated Lagoons               1,04 - 1,10        1,08
-Reed Beds                     1,02 - 1,08        1,035
-For a permanent bottom sealing of the reed bed, following methods could be considered.
-   Clay sealing (compacted soil sealing)
-   Polymer Foils/Geo textiles
-   Concrete sealing
-The geotextiles are cheaper than concrete sealings but geotextiles are still costlier than clay sealings. Irrespective of the type of sealings, the bottom of the reed bed should be made impervious to prevent percolation of untreated water.
-The substrate (media of the reed bed) is still subject among the experts in the field. The choices are:
-Pebbles, coarse sand and gravel  (no fine sand components are present)
-Soil with a high degree of fine sand.
-Many chose river sand with an uniformity coefficient of Uc = 3.1 and a theoretical diameter of d = 0,6 mm. The percolation calculated  permeability is Kf = 2 x 10<sup>-3</sup> m/s
-[[Category:Appropriate technology]]
 [[Category:Ecology]]
-[[Category:Sewerage]]
-[[Category:Waste treatment technology]]
 [[fr:Roselière]]