Treatment pond

A treatment pond treats water fouled by anaerobic bacteria. It is used mainly by tree nurseries, dairy farms and other agricultural companies near horse or cattle sheds or barns. The pond treats polluted stormwater and animal wastewater so that it may be returned to the environment as fertilizer and irrigation water.

Uses of treatment ponds

An ecological swimming pond

A treatment pond may be used in combination with a rainwater reservoir to form an ecological, self-purifying irrigation reservoir or swimming pond.^[1][2] A pond may dispose or treat industrial liquid wastes. An example is the Martinez, California treatment ponds developed by IT Corporation. Small-scale treatment can be done in small ponds if the effluent is given time to break into harmless nutrients. However, smaller ponds may need to be divided in much the same manner as septic tanks.

Set-up

Constructed wetlands

Urban areas

Three reedbed flow configurations are commonly in use. Each is being used in commercial systems (usually together with septic tanks).^[3] They are:

• Surface flow (SF) reedbeds
• Subsurface Flow (SSF) reedbeds
• Vertical Flow (VF) reedbeds

Different flow configurations for reedbed treatment.

All three are placed in a closed basin with a substrate. For most commercial purposes (e.g., agriculture) ponds are lined with rubber to ensure being watertight (essential in urban areas). The substrate can be gravel, sand or lavastone.

Design characteristics

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

Surface flow reedbeds use a horizontal flow of waste water between plant roots. They are no longer much used, as they need considerable space (A person requires 20 m² to purify the water they use.) They have increased smell and poorer purification in winter.^[4]

With subsurface flow reedbeds, the flow of waste water is between plant roots, but not at the water surface. This is more efficient, less smelly and less sensitive to winter conditions. The soil to purify water is 5–10 m² per person. Intakes, which can clog easily, are a potential problem.^[4]

Vertical flow reedbeds are similar to subsurface flow reedbeds (subsurface wastewater flow is present here as well). Therefore they have similar efficiency and winter hardiness. Wastewater flow is somewhat different though, as it is vertical. The water is distributed through a set of perforated distribution pipes in the top layer of gravel. The wastewater then passes a layer of fine sand mixed with iron and chalk and there it is purified by bacteria that live on the sand grains and in higher concentrations near the plant roots. The purified water is then collected in drainage pipes that are embedded in the bottom layer of gravel. Other than the two previous systems, this system almost makes exclusive use of fine sand to increase bacteria counts. Intake of oxygen into the water is better. Pumping is done in pulses to reduce obstructions with the intakes. Only 3 m² is needed to purify the water for one person.^[4]

Organisms

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.^[5]

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.^[6] At the time of implantation to water-purifying ponds, de-nutrified soil is used to prevent growth of algae and other unwanted organisms

Finishing

These systems, for example, aerate the water after the final reedbed using cascades such as flowforms before holding the water in a shallow pond.^[7] Primary treatments such as septic tanks, and pumps such as grinder pumps may be added.^[8]

Rooftop treatment ponds

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)^[9] or with plant-based ponds (as is being done by WaterWorks UK Grow System).^[10] Waterzuiveren.be^[11] Plants used include calamus, Menyanthes trifoliata, Mentha aquatica, ...^[12]

See also

• Detention pond
• Retention pond
• Settling pond

External links

• Pictures of a treatment pond
• SuSaNa treatment pond schematics

References

v t e 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 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