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A treatment pond is a type of pond which is constructed to treat lightly polluted water or wastewater. A treatment pond may be used in combination with a rainwater reservoir to form an ecological, self-purifying irrigation reservoir or swimming pond (natural pools). Rooftop water purifying ponds are being used on rooftops. These green roofs can be built from a simple substrate (as is being done in Dongtan)〔(Dongtan green roofs filter water )〕 or with plant-based ponds (as is being done by WaterWorks UK Grow System). Waterzuiveren.be Plants used include calamus, Menyanthes trifoliata, Mentha aquatica, ... ==Design== Usually, common reed or Phragmites australis are used in treatment ponds (e.g., in greywater treatment systems to purify wastewater). In self-purifying water reservoirs (used to purify rainwater), other plants are used as well. These reservoirs need to be filled with 1/4 lavastones and water-purifying plants. Treatment ponds use a wide variety of plants, depending on the local climate and other conditions. Plants are generally chosen which are indigenous, for environmental reasons and optimum performance. In addition to water purifying (de-nutrifying) plants, plants that supply oxygen, and shade are added in ecological water catchments, ponds. This allows a complete ecosystem. Local bacteria and non-predatory fish may be added to eliminate pests. The bacteria are usually grown by submerging straw in water and allowing bacteria from the surrounding air to form on it. Plants are divided in four water depth-zones: # A water depth from 0–20 cm. Iris pseudacorus, Sparganium erectum may be placed here (temperate climates). # A water depth from 40–60 cm. Stratiotes aloides, Hydrocharis morsus-ranae may be placed here (temperate climates). # A water depth from 60–120 cm. Nymphea alba, may be placed here (temperate climates). # A submerged water depth. Myriophyllum spicatum may be placed here (temperate climates). 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: Leuciscus leuciscus, Leuciscus idus, and Scardinius erythrophthalmus * Middle-swimmers: Rutilus rutilus * Bottom-swimming fish: Tinca tinca The plants are usually grown on coconut fibre.〔(Coconut growing medium used for water purifying plants )〕 At the time of implantation to water-purifying ponds, de-nutrified soil is used to prevent growth of algae and other unwanted organisms. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Treatment pond」の詳細全文を読む スポンサード リンク
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