Purpose of Aeration

What is the purpose of aeration. In this post, we will discuss the various objectives of water aeration:

Removal of organic matters

This is the main objective of aeration in wastewater treatment. It uses microorganism and oxygen to convert the disolved organic matters to carbon dioxide, water and sludge (dead microorganism).

Removal of Volatile Organic Compounds

Aeration can strip volatile organic compounds from water, the effectiveness of which depend on their solubility and their volatility. Laboratory studies have shown that aeration can be an extremely effective way of removing chlorinated organics from water.

Iron Removal

For domestic drinking water, iron is not an acceptable constituent. It imparts a bitter, metallic taste and stain wash basins, toilets, urinals, bath tubs, showers, tiled floors and walls, cloths, in fact, everything it comes in contact with. Iron concentration exceeding 0.2 to 0.3 mg/l may be objectionable even though its presence is not objectionable from the hygienic point of view.

Aeration is also used for oxidation of iron in the water into compounds which are subsequently removed by filtration. Iron filtration operate on the principal of oxidizing the iron to convert it from a ferrous (dissolved or soluble) state to a ferric or undissolved state. Once in the ferric state, the insoluble iron compounds can be filtered out. For best results, the pH of the water should be between 6.5 and 10.0. The higher the pH, the faster the dissolved ferrous state can be converted to the insoluble ferric state.

Sulfur Removal

Hydrogen Sulfite or H₂S, while not a health hazard, cause the rotten egg smell in water which people find offensive. It can be partially removed by aeration. Sulfur dioxide or SO₂ and other gasses are more soluble in air than water so are transferred to the rising air bubbles

Reduce Algae

Aeration removes nitrogen, ammonia and soluble phosphate which are food for algae. The deprivation of food reduces algae growth. Aeration also helps aerobic bacteria, which have a very robost appetite for organic matters, to thrive. Aerobic bacteria are more efficient consumer of nutrients and thus their consumption by the aerobic bacteria lead to food starvation by the algae.