Aeration Technology (Right Sizing of Equipment)

In wastewater system, the role and development of Aeration Technology is to work on to increase contact of air and water, aimed primarily towards increasing oxygen content dissolved in water. Apart from that, another goal of aeration can also be applied towards removal of undesirable gases present in wastewater such as methane and also CO2. Aeration processes can be a simple setup but it can also be combined with other unit of operations whether it is biological or chemical in nature, but limited to our scope of discussion here on wastewater system, we will focus on aeration involving biochemical oxidation which is mainly to assist in COD reduction.

Aeration techniques available for wastewater treatment will require aerator units capable of handling huge capacities and at the same time, higher efficiencies are obtained. In order to achieve this, the technologies are developed with consideration focused on using the least amount of energy to achieve the same desired results. The most commonly used type of equipment are mainly centered around diffused aerators (also known as submerged aerator) and surface aerators whereby both units are equally functional. To differentiate between those two, a surface aerator is actually made up of a motor driven impeller usually placed right beneath the basin surface and recently newly introduced design will actually pump up large volumes of water and disperse it so that this will increase contact of water to atmosphere.

Sometimes a more efficient system can also make use of both types of setup by combining submerged and surface aeration device together. Since it employs both techniques to achieve maximum air and water contact, this system is more preferred and is usually selected for use in deep aeration basin that handles huge volume of wastewater per day. As an engineer involved directly with running of operation, it is imperative that sizing of aeration equipment should also be done properly. To understand the overall concept, any aeration requirement can be defined as degree of oxygen deficiency in the wastewater and also the reactions happening in the system. However, in the context of treatment processes, it can also be interpreted as functions of BOD loading and measurement on the extent of sludge oxidation.

As a reference, you can always use the below equation to calculate horsepower requirements.

hp= Q x d x L /24 x q

Q = flow, gallons per day
d = density of liquid, lb/gal
L= BOD, ppm or mg/L
q = oxygen transfer rate in lb O2/hp-h

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