Air aeration is the process of increasing or maintaining water oxygen saturation in natural and artificial environments.
Video Water aeration
Water quality
Air aeration is often required in water bodies that suffer from hypoxia or anoxic conditions, often caused by upstream human activities such as sewerage, agricultural runoff, or over-baiting a fishing lake. Aeration can be achieved by infusion of air to the bottom of a lake, lagoon or pond or by the surface agitation of such fountains or sprays to allow the exchange of oxygen on the surface and the release of gases such as carbon dioxide, methane. or hydrogen sulfide.
Dissolved Oxygen (DO) is a major contributor to water quality. Not only fish and most other aquatic animals need it, but aerobic bacteria help to break down organic matter. When the oxygen concentration becomes low, anoxic conditions can develop that can decrease the body's ability to support life.
Maps Water aeration
Aeration method
Any procedure in which oxygen is added to water can be considered a type of water aeration. This being the only criterion, there are various ways to aerate the water. It falls into two broad areas - surface aeration and subsurface aeration . There are a number of techniques and technologies available for both approaches
Natural aeration
Natural aeration is a kind of sub-surface and surface aeration. This can happen through subsurface water plants. Through the natural process of photosynthesis, aquatic plants release oxygen into the water by providing the oxygen necessary for fish to live and aerobic bacteria to break down excess nutrients.
Oxygen can be moved into the water when the wind disrupts the surface of the body of water and natural aeration can occur through the movement of water caused by inflows, waterfalls, or even a strong flood.
In large bodies of water, the autumn shift can introduce oxygen-rich water into the oxygen-poor Hypolimnion.
Aeration surface
Low speed surface aircrafts
Low speed surface aerators are tools for high efficiency biological aeration. These devices are often in steel protected by an epoxy coating and produce high torque. The mixing of water volume is very good. The general strength will range from 1 to 250kw per unit with efficiency (SOE) of about 2 kgO2/kw. Low speed aerators are used mostly for aeration of biological plants for water purification. The higher the higher the SOE diameter and the mixing
Fountains
The fountain consists of a motor that drives a rotating impeller. The impeller pumps water from the first few meters of water and ejects it into the air. This process uses air-water contact to transfer oxygen. As water is pushed into the air, it breaks into tiny droplets. Collectively, these small droplets have large surface areas where oxygen can be transferred. Upon return, these droplets mix with the rest of the water and thus transfer their oxygen back to the ecosystem.
Fountains are a popular method of surface aerators because of the aesthetic appearance they offer. However, most fountains can not produce large amounts of oxygen water. Also, running electricity through water to a fountain can be a safety hazard.
Aerator floating surface
Floating surface aerators work in a similar way to fountains, but they do not offer the same aesthetic appearance. They take water from the first 1-2 meters of the water body and utilize the water-water contact to transfer oxygen. Instead of pushing water into the air, they disturb water on the surface of the water. Floating surface aerators are also powered by electricity on the coast. Aerator surfaces are confined to small areas because they can not add circulation or oxygen to more than 3 meters radius. This circulation and oxygenation is then limited to the first part of the water column, often leaving the underside unaffected. This is the most important in the world. Low-speed surface aircrafts can also be mounted on buoys.
Aerator paddlewheel
Paddlewheel aerators also utilize air contact to water to transfer oxygen from the atmosphere air to water bodies. They are most commonly used in aquaculture (raising aquatic animals or aquatic cultivation for food). Built from a hub with a mounted pedal, this aerator is usually driven by a power take-off tractor (PTO), a gas engine, or an electric motor. They tend to be mounted on buoys. Electricity forces the oars to spin, shake water and allow the transfer of oxygen through air-water contact. As each new part of the water flares, it absorbs oxygen from the air and then after it returns to the water, returns it to the water. In this case the paddlewheel aeration works very similar to the floating aerator surface.
Sub subsurface
Under the aeration the surface attempts to release the bubbles at the bottom of the body of water and allows them to rise with the force of buoyancy. The diffused aeration system utilizes bubbles to air and mix water. Substitution of water from bubble expulsion can cause mixing action to occur, and contact between water and bubbles will result in oxygen transfer.
Aeration jet
Under aeration surfaces can be achieved by using a jet aerator, which aspirates air, in the Venturi principle way, and injects air into the liquid.
Aeration of rough bubbles
Rough bubble aeration is a type of suburban aeration where air is pumped from air compressors in air. through the hose to the unit placed at the bottom of the water body. This unit releases a rough bubble (diameter greater than 2mm), which releases oxygen when they come in contact with water, which also contributes to the mixing of the laminated layer of the lake. With the release of large bubbles from the system, there is a turbulent displacement of water that results in the mixing of water. Compared with other aeration techniques, rough bubble aeration is very inefficient in the way oxygen transfers. This is due to the large diameter and relatively small collective surface area of ​​the bubbles
Aeration of fine bubbles
Aeration of fine bubbles is an efficient way to transfer oxygen to the body of water. A compressor on the beach pumps air through the hose, which is connected to an underwater aeration unit. Attached to the unit are a number of diffusers. These diffusers come in the form of discs, plates, tubes or hoses made of silica bonded glass, porous ceramic plastic, PVC or perforated membranes made of EPDM rubber (ethylene propylene diene monomer). The air pumped through the diffuser membrane is released into the water. This bubble is known as a fine bubble . The EPA defines a fine bubble as something smaller than 2mm in diameter. This type of aeration has a very high oxygen transfer efficiency (OTE), sometimes as high as 15 pounds of oxygen/(horsepower * hours) (9.1 kilograms oxygen/(kilowatt * hour)). On average, the aerated air aeration spreads about 2-4 cfm (air cubic feet per minute) (56.6-113.3 liters of air per minute), but some operate at levels as low as 1 cfm (28.3 L/min) or as high as 10 cfm (283 L/min).
Aerated diffused bubbles are able to maximize the bubble surface area and thereby transfer more oxygen to the water per bubble. In addition, smaller bubbles take longer to reach the surface so that not only the maximized surface area but also the number of seconds each bubble is spent in the water, resulting in more time to transfer oxygen to the water. As a general rule, smaller bubbles and deeper release points will result in greater oxygen transfer rates.
However, almost all of the oxygen dissolved into the water from the air bubbles occurs when the bubbles are being formed. Only a negligible amount occurs during the transit bubble to the water surface. This is why the aeration process that makes a lot of small bubbles is better than the ones that make the little smaller. The breakup of larger bubbles into smaller bubbles also repeats this formation and transfer process.
One disadvantage for fine aeration bubbles is that ceramic diffusers membranes can sometimes clog and must be cleaned to keep them working at optimum efficiency. In addition, they lack the ability to mix as well as other aeration techniques, such as rough bubble aeration.
Lake Destruction
Circulators are usually used to mix ponds or lakes and thereby reduce thermal stratification. Once the water supply reaches the surface, the air-water interface facilitates the transfer of oxygen to the lake water.
Natural resource and environmental managers have long been challenged by problems caused by the thermal stratification of lakes. Dead-off fish have been directly linked to thermal gradients, stagnation, and ice cover. Excessive plankton growth can limit the use of lake recreation and commercial lake water use. With severe thermal stratification in the lake, the quality of drinking water can also be affected. For fisheries managers, the spatial distribution of fish in the lake is often influenced by thermal stratification and in some cases may indirectly lead to major fish mortality which is very important.
One common tool used to reduce the severity of the lake management problem is to eliminate or reduce thermal stratification through aeration. Many types of aeration equipment have been used to reduce or eliminate thermal stratification. Aeration has met with some success, although it rarely proves to be a panacea.
Oxygenation barge
During heavy rains, London waste storm pipes overflowed into the Thames River, sending dissolved oxygen levels down and threatening the species it supports. Two special McTay Marine vessels, the thermal oxygenation bar Thames Bubbler and Thames Vitality are used to fill the oxygen level, as part of a continuous battle to clear the river, which now supports 115 fish species and hundreds more invertebrates, plants and birds.
The concentration of dissolved oxygen in Cardiff Bay is maintained at or above 5 mg/L. Compressed air is pumped, from five locations around the Bay, through a series of steel-reinforced steel pipes, which are laid on the bed of the Bay and the Taff and Ely Rivers. It connects to about 800 diffusers. Sometimes this is not enough and the Port Authority uses a mobile oxygenation barge built by McTay Marine with liquid oxygen stored in the tank. Liquid oxygen is passed through an electrically heated vapouriser and gas is injected into the pumped water stream from, and back to, the bay. The barge is capable of dissolving up to 5 tons of oxygen in 24 hours.
Similar options have been proposed to help rehabilitate Chesapeake Bay where the main problem is the lack of filtering organisms such as oysters responsible for keeping the water clean. Historically the Bay oyster population is in the tens of billions, and they circulate the entire Gulf volume in a matter of days. Due to pollution, disease and excessive harvest their population is a fraction of their historical level. Water that was once clean for meters is now so turbid and sediment builds up that a wader may lose sight of their feet before their knees are wet. Oxygen is usually supplied by "Submerged Aquatic Vegetation" (SAV) through photosynthesis but pollution and sediment have reduced plant populations as well. Resulting in decreased dissolved oxygen levels that make the bay area unsuitable for aquatic life. In symbiotic relationships, plants provide the oxygen needed for underwater organisms to proliferate, instead filter feeders maintain water hygiene and clear enough for plants to have adequate access to sunlight. Researchers have proposed that oxygenation through artificial means as a solution to help improve water quality. Aeration of hypoxic water bodies seems an interesting solution and has been successful many times in freshwater ponds and small lakes. But no one is doing aeration project as wide as the estuary.
Water treatment aeration
Many water treatment processes use various forms of aeration to support biological oxidative processes. A typical example is the activated sludge which can use either aerated bubbles or rough or mechanical aeration cones which make up the liquor mixture from the bottom of the processing tank and remove it through the air where oxygen is introduced into the liquor.
See also
- Aeration lagoon
- Lake ecosystem
- Limnology
References
Source of the article : Wikipedia
0 Comments