Water aeration
Aeration techniques are commonly used in pond, lake, and reservoir management to address low oxygen levels or algal blooms.
Not only do fish and most other aquatic animals need oxygen, aerobic bacteria help decompose organic matter.
When oxygen concentrations become low, anoxic conditions may develop which can decrease the ability of the water body to support life.
[4] The effectiveness of a surface aerator is limited to a small area as they are unable to add circulation or oxygen to much more than a 3-metre radius.
Paddlewheel aerators also utilize air-to-water contact to transfer oxygen from the air in the atmosphere to the water body.
Electricity forces the paddles to turn, churning the water and allowing oxygen transfer through air-water contact.
Subsurface aeration seeks to release bubbles at the bottom of the water body and allow them to rise by the force of buoyancy.
The unit expels coarse bubbles (more than 2mm in diameter),[7] which release oxygen when they come into contact with the water, which also contributes to a mixing of the lake's stratified layers.
These diffusers come in the shape of discs, plates, tubes or hoses constructed from glass-bonded silica, porous ceramic plastic, PVC or perforated membranes made from EPDM (ethylene propylene diene Monomer) rubber.
As a general rule, smaller bubbles and a deeper release point will generate a greater oxygen transfer rate.
[9] One of the drawbacks to fine bubble aeration is that the membranes of ceramic diffusers can sometimes clog and must be cleaned in order to keep them working at their optimum efficiency.
Natural resource and environmental managers have long been challenged by problems caused by thermal stratification of lakes.
[11] One commonly-used tool to reduce the severity of these lake management problems is to eliminate or lessen thermal stratification through aeration.
[10] During heavy rain, London's sewage storm pipes overflow into the River Thames, sending dissolved oxygen levels plummeting and threatening the species it supports.
[15] Two dedicated McTay Marine vessels, oxygenation barges Thames Bubbler and Thames Vitality are used to replenish oxygen levels, as part of an ongoing battle to clean up the river, which now supports 115 species of fish and hundreds more invertebrates, plants and birds.
Liquid oxygen is passed through an electrically heated vapouriser and the gas is injected into a stream of water which is pumped from, and returned to, the bay.
[16] Similar options have been proposed to help rehabilitate the Chesapeake Bay where the principal problem is lack of filter-feeding organisms such as oysters responsible for keeping the water clean.
Water that was once clear for meters is now so turbid and sediment-ridden that a wader may lose sight of their feet before their knees are wet.
[citation needed] Oxygen is normally supplied by submerged aquatic vegetation via photosynthesis but pollution and sediments have reduced the plant populations , resulting in a reduction of dissolved oxygen levels, rendering areas of the bay unsuitable for aerobic aquatic life.
Aeration of hypoxic water-bodies seems an appealing solution and it has been tried successfully many times on freshwater ponds and small lakes.
