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A '''treatment pond''' | A '''treatment pond''' is a simple [[bioreactor]] for treating [[wastewater]]. It is simply a pond with [[bacteria]] and other [[microorganisms]] from the environment and the wastewater performing the treatment. The bacterial concentration is low compared to other biological treatment processes such as [[activated sludge]], and the treatment time is also longer. | ||
The wastewater may contain organic toxins, sediment, and/or [[anaerobic]] [[bacteria]]. The organic components of the wastewater are converted by the microorganisms (mainly bacteria), producing solids, [[carbon dioxide]] and [[water]]. Solids (including bacterial solids) settle out due to the very slow flow and the shallowness of the water. | |||
== | == Role of treatment ponds == | ||
Treatment ponds are used for [[agricultural waste]], and sometimes as part of the processing of waste from [[food production]]. Industrial liquid wastes may be suitable, if there is organic content, but at a low concentration where other forms of biological treatment are inefficient. | |||
{{ | |||
They may also treat polluted [[stormwater]]. | |||
Depending on the quality of the output, it may be suitable as [[fertilizer]] and [[irrigation]] water. | |||
A treatment pond may be used in combination with a [[rainwater]] reservoir to form a self-purifying irrigation reservoir or swimming pond.<ref>[http://www.oieau.fr/ciedd/contributions/atriob/contribution/russian.htm Ecologic water basins used for agriculture/irrigation]</ref><ref>[http://www.swimpond.com/pools_or_ponds.html reservoirs made self-purifying through addition of treatment pond]</ref> Small-scale treatment can be done in small pond if the [[Glossary_of_sustainability_terms#E|effluent]] is given adequate time to break down the wastewater. Smaller ponds may need to be divided in a similar way to [[septic tank]]s. | |||
==Constructed wetlands== | |||
{{main|Constructed wetlands}} | |||
A '''constructed wetland''' is a kind of treatment pond with an emphasis on supporting a complex ecosystem within and around the ponds. | |||
== Design == | |||
=== Three types of reedbed === | |||
[[File:Treatment-pond-raster.png|thumb|right|150px|The 3 treatment set-ups mostly employed]] | [[File:Treatment-pond-raster.png|thumb|right|150px|The 3 treatment set-ups mostly employed]] | ||
There are three kinds of [[reedbed]] setups. They can be used in commercial systems (usually with septic tanks).<ref>[http://www.certipro.be/docs/Certificering%20van%20plantenwaterzuiveringssystemen.pdf reedbed descriptions]</ref> They are: | |||
* Surface flow (SF) reedbeds | * Surface flow (SF) reedbeds | ||
* Subsurface Flow (SSF) reedbeds | * Subsurface Flow (SSF) reedbeds | ||
* Vertical Flow (VF) reedbeds | * Vertical Flow (VF) reedbeds | ||
The reedbeds grow in a closed basin with a substrate medium. For most commercial purposes, ponds are lined in order to be watertight. Rubber can be used. Preventing leakage is essential in urban areas or close to residences. Substrate medium can be [[gravel]], [[sand]] and/or [[lavastone]]. | |||
[[Image:Lavafilter.jpg|thumb|right|250px|A treatment pond aligned next to a [[irrigation]] reservoir, forming a self-purifying reservoir]] | [[Image:Lavafilter.jpg|thumb|right|250px|A treatment pond aligned next to a [[irrigation]] reservoir, forming a self-purifying reservoir]] | ||
In '''surface flow reedbeds''' a horizontal flow carries waste water between the plant roots. They are used much less in recent years, as they need a large area area, around 20 m<sup>2</sup> per person for domestic wastewater. In cold weather smell and poorer purification are problems.<ref name="reedbed secriptions">[http://www.certipro.be/docs/Certificering%20van%20plantenwaterzuiveringssystemen.pdf reedbed secriptions]</ref> | |||
In '''subsurface flow reedbeds''', wastewater flows between plant roots ''below'' the water surface. This is more efficient, requiring 5–10 m<sup>2</sup> per person. There is less smell and less sensitivity to cold or winter conditions. Clogging intakes are a potential problem.<ref name="reedbed secriptions"/> | |||
'''Vertical flow reedbeds''' are similar to subsurface flow reedbeds, and they have similar advantages in efficiency (only 3 m<sup>2</sup> is needed per person.<ref name="reedbed secriptions"/>) and cold-weather tolerance. Wastewater flow is vertical, aided by a [[pump]] from the bottom.{{fact}} Vertical reedbeds generally use a fine [[sand]] to allow greater bacterial concentration. Oxygenation of the water is better.{{fact}} Pulsed pumping reduces obstructions in the intakes. | |||
=== Organisms === | |||
Common reed ([[Phragmites]]{{w|Phragmites}}) are widely used in treatment ponds (e.g., in [[greywater treatment]] systems to purify wastewater). | |||
In self-purifying water [[reservoirs]] (for purifying rainwater prior to distribution), other plants (ie Iris pseudacorus,... )are also used. One approach is to fill the reservoirs with 1/4 lavastones and water-purifying plants.<ref>[http://www.stowa-selectedtechnologies.nl/Sheets/Sheets/Lava.Filters.html Overview of lavafilters]</ref>{{expand}} | |||
A wide variety of plants are used, and these depending on the local conditions, including climate. Indigenous plants may be preferred for environmental reasons and suitability to the local environment. Plants that supply oxygen and shade are valuable, creating an [[ecosystem]] (=submerged plants). [[Bacteria]] and suitable fish may be added to help eliminate pests. Bacteria may be grown by placing [[straw]] in water and allowing bacteria from the ambient air to grow on it. Plants are divided in four water depth-zones: | |||
# A water depth from | # A water depth from 0–20cm. | ||
# A water depth from | # A water depth from 40–60cm. | ||
# A water depth from | # A water depth from 60–120cm. | ||
# | # Deeper water | ||
Three non-predatory fish (surface, bottom and ground-swimmers) are chosen. This ensures the fish 'get along'. Examples for temperate climates are: | Three non-predatory fish (surface, bottom and ground-swimmers) are chosen. This ensures the fish 'get along'. Examples for temperate climates are: | ||
* Surface swimming fish | * Surface swimming fish | ||
* Middle-swimmers | * Middle-swimmers | ||
* Bottom-swimming fish | * Bottom-swimming fish | ||
[[Coconut]] fibre.<ref>[http://www.lukmertens.be/kwekerij.html Coconut growing medium used for water purifying plants]</ref> can be used as a growing medium for propagating the plants. | |||
The | The use of de-nutrified soil can prevent growth of [[algae]] and other unwanted [[organisms]] | ||
==Finishing== | :''See also [[Wikipedia:Organisms used in water purification]] | ||
=== Finishing === | |||
A final, shallow "polishing pond" is often used. Aeration can be carried out with cascades before passing into the final pond, or with mechanical aerators within the ponds.<ref>[http://www.sheepdrove.com/article.asp?art_id=115] reedbed and flowform cascade polishing, Sheepdrove Organic Farm, England</ref> | |||
=== Combined systems === | |||
Primary treatments such as [[anaerobic digesters]] or [[septic tanks]] may be used for the initial stages of treatment where [[biochemical oxygen demand]] is sufficiently high. [[Grinder pumps]] may be used before treating a lumpy effluent, to create a slurry which is more easily processed by the bacteria. | |||
==Rooftop treatment ponds== | ==Rooftop treatment ponds== | ||
Rooftop water purifying ponds can be built using a simple substrate, as is being done in the Dongtan eco-city.<ref>[http://www.eukn.org/eukn/themes/Urban_Policy/Urban_environment/Environmental_sustainability/dongtan-eco-city_1348.html Dongtan green roofs filter water]</ref> | |||
== | Plant-based ponds have also been designed for roofs,<ref>[http://www.toontoelen.be/index.php?option=com_content&task=view&id=684&Itemid=58 Description of plants used in water-purifying rooftop ponds]</ref> e.g. WaterWorks UK Grow System)<ref>[http://www.wwuk.co.uk/grow.htm WWUK rooftop water purification with plants]</ref> and Waterzuiveren of Belgium{{fact}}<ref>[http://www.waterzuiveren.be/concepten/dakvijvers Waterzuiveren.be building water-purifying roofponds]</ref> | ||
* [[ | == See also == | ||
*[[AT CAD Team/AT settlement water distribution system|AT settlement water distribution system]] | |||
*[[Greywater treatment]] | |||
*[[Constructed wetlands]] | |||
== Gallery == | |||
<gallery> | |||
File:AT_Vertical_Flow_reedbed.png|A simple reed bed | |||
</gallery> | |||
== External links == | == External links == | ||
* [[Wikipedia:Treatment pond]] | |||
* [http://www.facstaff.bucknell.edu/kirby/4ponds.html Pictures of a treatment pond] | * [http://www.facstaff.bucknell.edu/kirby/4ponds.html Pictures of a treatment pond] | ||
==References== | ==References== | ||
{{Reflist}} | {{Reflist}} | ||
[[Category:Anaerobic digestion]] | [[Category:Anaerobic digestion]] | ||
[[Category:Sewerage infrastructure]] | [[Category:Sewerage infrastructure]] | ||
[[Category:Water treatment]] | [[Category:Water treatment]] |
Revision as of 10:14, 16 July 2013
A treatment pond is a simple bioreactor for treating wastewater. It is simply a pond with bacteria and other microorganisms from the environment and the wastewater performing the treatment. The bacterial concentration is low compared to other biological treatment processes such as activated sludge, and the treatment time is also longer.
The wastewater may contain organic toxins, sediment, and/or anaerobic bacteria. The organic components of the wastewater are converted by the microorganisms (mainly bacteria), producing solids, carbon dioxide and water. Solids (including bacterial solids) settle out due to the very slow flow and the shallowness of the water.
Role of treatment ponds
Treatment ponds are used for agricultural waste, and sometimes as part of the processing of waste from food production. Industrial liquid wastes may be suitable, if there is organic content, but at a low concentration where other forms of biological treatment are inefficient.
They may also treat polluted stormwater.
Depending on the quality of the output, it may be suitable as fertilizer and irrigation water. A treatment pond may be used in combination with a rainwater reservoir to form a self-purifying irrigation reservoir or swimming pond.[1][2] Small-scale treatment can be done in small pond if the effluent is given adequate time to break down the wastewater. Smaller ponds may need to be divided in a similar way to septic tanks.
Constructed wetlands
A constructed wetland is a kind of treatment pond with an emphasis on supporting a complex ecosystem within and around the ponds.
Design
Three types of reedbed
There are three kinds of reedbed setups. They can be used in commercial systems (usually with septic tanks).[3] They are:
- Surface flow (SF) reedbeds
- Subsurface Flow (SSF) reedbeds
- Vertical Flow (VF) reedbeds
The reedbeds grow in a closed basin with a substrate medium. For most commercial purposes, ponds are lined in order to be watertight. Rubber can be used. Preventing leakage is essential in urban areas or close to residences. Substrate medium can be gravel, sand and/or lavastone.
In surface flow reedbeds a horizontal flow carries waste water between the plant roots. They are used much less in recent years, as they need a large area area, around 20 m2 per person for domestic wastewater. In cold weather smell and poorer purification are problems.[4]
In subsurface flow reedbeds, wastewater flows between plant roots below the water surface. This is more efficient, requiring 5–10 m2 per person. There is less smell and less sensitivity to cold or winter conditions. Clogging intakes are a potential problem.[4]
Vertical flow reedbeds are similar to subsurface flow reedbeds, and they have similar advantages in efficiency (only 3 m2 is needed per person.[4]) and cold-weather tolerance. Wastewater flow is vertical, aided by a pump from the bottom.[verification needed] Vertical reedbeds generally use a fine sand to allow greater bacterial concentration. Oxygenation of the water is better.[verification needed] Pulsed pumping reduces obstructions in the intakes.
Organisms
Common reed (PhragmitesW) are widely used in treatment ponds (e.g., in greywater treatment systems to purify wastewater).
In self-purifying water reservoirs (for purifying rainwater prior to distribution), other plants (ie Iris pseudacorus,... )are also used. One approach is to fill the reservoirs with 1/4 lavastones and water-purifying plants.[5]
A wide variety of plants are used, and these depending on the local conditions, including climate. Indigenous plants may be preferred for environmental reasons and suitability to the local environment. Plants that supply oxygen and shade are valuable, creating an ecosystem (=submerged plants). Bacteria and suitable fish may be added to help eliminate pests. Bacteria may be grown by placing straw in water and allowing bacteria from the ambient air to grow on it. Plants are divided in four water depth-zones:
- A water depth from 0–20cm.
- A water depth from 40–60cm.
- A water depth from 60–120cm.
- Deeper water
Three non-predatory fish (surface, bottom and ground-swimmers) are chosen. This ensures the fish 'get along'. Examples for temperate climates are:
- Surface swimming fish
- Middle-swimmers
- Bottom-swimming fish
Coconut fibre.[6] can be used as a growing medium for propagating the plants.
The use of de-nutrified soil can prevent growth of algae and other unwanted organisms
Finishing
A final, shallow "polishing pond" is often used. Aeration can be carried out with cascades before passing into the final pond, or with mechanical aerators within the ponds.[7]
Combined systems
Primary treatments such as anaerobic digesters or septic tanks may be used for the initial stages of treatment where biochemical oxygen demand is sufficiently high. Grinder pumps may be used before treating a lumpy effluent, to create a slurry which is more easily processed by the bacteria.
Rooftop treatment ponds
Rooftop water purifying ponds can be built using a simple substrate, as is being done in the Dongtan eco-city.[8]
Plant-based ponds have also been designed for roofs,[9] e.g. WaterWorks UK Grow System)[10] and Waterzuiveren of Belgium[verification needed][11]
See also
Gallery
-
A simple reed bed
External links
References
- ↑ Ecologic water basins used for agriculture/irrigation
- ↑ reservoirs made self-purifying through addition of treatment pond
- ↑ reedbed descriptions
- ↑ 4.0 4.1 4.2 reedbed secriptions
- ↑ Overview of lavafilters
- ↑ Coconut growing medium used for water purifying plants
- ↑ [1] reedbed and flowform cascade polishing, Sheepdrove Organic Farm, England
- ↑ Dongtan green roofs filter water
- ↑ Description of plants used in water-purifying rooftop ponds
- ↑ WWUK rooftop water purification with plants
- ↑ Waterzuiveren.be building water-purifying roofponds