Wastewater Treatment Plants and Aeration Airflow

Wastewater Treatment Plants and Aeration Airflow

How aeration works

What is Aeration Flow?
At wastewater treatment facilities, aeration is used to introduce air into the wastewater to create an environment that promotes the growth of microorganisms to decompose the organic waste. The oxygen feeds or nourishes microorganisms within the basin, so the bacteria thrive and consume suspended particulates.

This may be achieved either through a mechanical agitation system or a subsurface air system. A mechanical system uses blades, propellers or brushes to agitate the wastewater to introduce air from the atmosphere. In a subsurface system, the air is introduced by blowers and diffusers submerged in the wastewater. Air blowers may feed the main header which serves multiple aeration basins. From the main header, the air flows to each aeration basin or each zone in an aeration basin. Depending on the design, flow meters may be used to measure the flow to each aeration basin or individual zones in each basin. The total amount of air flowing to the aeration basins is controlled by the dissolved oxygen (DO) meter in the basin.

In older systems there was little control over air flow, as it was assumed that the more air flow, the better the decomposition. This viewpoint, however, has changed given the high cost of energy. Thermal mass flow meters may be installed in the main header to measure the total air flow from the blower/compressor. In this case, there is no control of the air flow to each basin; the meter is merely monitoring air flow to check the performance of the blower. Optionally, a flow meter may be installed on each branch line leading to an individual basin where the flow meter is used for balancing the air flow between basins or, in some cases, controlling the flow to each aeration basin.