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How to Choose between Mechanical Surface Aeration vs. Diffuser Aeration

The two most common biological treatment methods for inserting oxygen into wastewater are mechanical surface aerators and fixed-to-the-floor fine bubble diffusers. 

Surface aerators throw the water into the air, the travelling droplets that are in contact with the atmospheric air typically oxygenate to at least half- saturation. As soon as they land back in the water they mix with the water bulk, producing a typical DO (dissolved oxygen) pattern.

The advantages of mechanical surface aerators include easy installation, and as they float, they can aerate any type of basin. But there are many downsides to this technology. Because the operating principle of surface aerators is a mechanical engine that spins a rotor inside of the wastewater, it tends to breakdown, needing frequent maintenance. In order to conduct maintenance, the operator needs to enter the wastewater – a huge health & safety risk. In addition, surface aerators are not the most efficient method to aerate wastewater. When comparing aeration efficiency, the parameter used is called SAE (Standard Aeration Efficiency). SAE measures the amount of oxygen per hour per kW, or in other words, how much oxygen is achieved per each kW expenditure. The typical SAE for surface aerators is between 1.5-2 kgO2/ hr kW. In contrast to this, with Fine Bubble diffusers the SAE tends to be 3.5-4 kgO2/hr kW.

Most Fine Bubble diffusers are fixed to the floor, therefore, they require an empty aeration basin for installation and maintenance. They are also mostly only suitable for reactors with a levelled floor. Mapal Aeration Solutions has developed floating Fine Bubble diffusers, that combine the advantages of surface aerators with the aeration efficiency of Fine Bubble aeration. Our system is easily installed with a mobile crane in full, active, aeration basins.  Installation is conducted directly into the wastewater, with no need to drain the facility, and no people in the water – an enormous Health & Safety advantage .

As the units float, they are suitable for any aeration reactor, tank, or lagoon. The units can work alongside or above any other existing aeration, for supplemental oxygen during peak season, or to support malfunctioning equipment. We can also provide a full aeration solution for new builds, with the advantage of easy maintenance, keeping aeration efficiency throughout the product lifecycle.

The aeration units are constructed from stainless steel, making them extremely robust. Therefore, they can be removed from the wastewater for maintenance with a mobile crane, without breaking or sagging, and following treatment be returned to the wastewater.