Treatment pond

A treatment pond next to an irrigation reservoir, forming a self-purifying reservoir

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).^[1][2]

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)^[3] or with plant-based ponds (as is being done by WaterWorks UK Grow System).^[4] Waterzuiveren.be^[5] Plants used include calamus, Menyanthes trifoliata, Mentha aquatica, ...^[6]

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.^[7]

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:

1. A water depth from 0–20 cm. Iris pseudacorus, Sparganium erectum may be placed here (temperate climates).
2. A water depth from 40–60 cm. Stratiotes aloides, Hydrocharis morsus-ranae may be placed here (temperate climates).
3. A water depth from 60–120 cm. Nymphea alba, may be placed here (temperate climates).
4. 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.^[8] At the time of implantation to water-purifying ponds, de-nutrified soil is used to prevent growth of algae and other unwanted organisms.

See also

• Constructed wetland
• Detention pond
• Green roof
• Natural pool
• Retention pond
• Settling pond

References

Ponds, pools and puddles Ponds Ash pond Balancing pond Ballast pond Beel Cooling pond Detention pond Dew pond Evaporation pond Facultative pond Garden pond Ice pond Immersion pond Kettle pond Log pond Melt pond Mill pond Raceway pond Retention pond Sag pond Salt evaporation pond Sediment pond Settling pond Solar pond Stabilization pond Stepwell Stew pond Stormwater management pond Polishing pond Tailings pond Tarn Treatment pond Waste pond Pools Anchialine pool Brine pool Natural pool Plunge pool Reflecting pool Spent fuel pool Stream pool Swimming pool Tide pool Vernal pool Puddles Bird bath Coffee ring effect Puddle Puddles on a surface Seep puddle Biota Beaver pond Common pond skater Common puddle frog Duck pond Fish pond Goldfish pond Koi pond Lotus Pond heron Pond lily Pond snail Pond turtle Pondweed Ecosystems Freshwater ecosystem Lake ecosystem Lentic ecosystem Pond ecosystem Related topics Aerated pond Bakki shower Big fish–little pond Body of water Full pond Hydric soil Phytotelma Water aeration Pond of Abundance Pond liner Ponding The Pond Puddle (M C Escher) Spring Swimming hole Water garden Water Lilies (Monet) Water well