At wastewater treatment plants an air flow meter may be used to measure airflow to deliver optimum flow which saves money in the process of breaking down sewage.

Aeration Air Flow Meters

The first step in the breakdown of raw sewage occurs in the aeration basin. Blowers are used to inject aeration air through headers at the bottom of the basin. The amount of air injected is based on obtaining a desired level of dissolved oxygen that is determined by a dissolved oxygen meter (DO meter);  using the signal from the air flow meters as a trim in the control circuit.

Wastewater Treatment Aeration Basin

Wastewater treatment plants commonly operate the blowers at a steady rate that provides a DO level higher than the desired value. These facilities are finding that by controlling the blower air flow the overall power consumption can be greatly reduced. A Sage Thermal Mass Flow Meter is ideal for measuring the flow into the aeration basin; the instrument is easy to install, provides a mass flow measurement and does not create any pressure drop.

Aeration Flow

The typical plant will have multiple blowers flowing into a common header then flowing into multiple aeration basins. Each basin may have multiple lines supplying air to the headers at the bottom of the aeration basins. In addition to using thermal mass flow meters for the overall air flow rate, thermal flow meters are used to measure the flow rate to each basin to ensure equal distribution of the air flow. In some instances the flow in each drop to the diffusers is measured, which makes sure equal amounts of air are sent to the basins and verifies that the air is distributed evenly throughout the basin.