Using Air Flow Meters on Aeration Diffusers Improves Wastewater Treatment Efficiency - Steve Craig

Wastewater treatment plants (Fig 1 and 2) use different treatment processes to eliminate organic pollutants in the wastewater. One of the most common processes is the activated sludge method, which biologically treats the wastewater through the use of large aeration basins. This process requires the pumping of compressed air into the aeration basins where a diffuser system ensures the air is distributed evenly for optimum treatment.

The activated sludge method introduces microorganisms into the aeration basins that biologically decompose the organics in the wastewater. These microorganisms require air to survive and depend on the aeration systemto provide the right amount of air necessary for themto thrive and consume the organics in the wastewater. Eventually, over a period of time, they flocculate into a mass and settle to the bottom of the basin along with the non-biodegradable solids.

Compressed air is typically used to provide the air to the aeration basins. Controlling the proper amount of air that is released into the aeration basins is essential because it controls the growth of microorganisms that treat the wastewater. Flow meters are typically installed in the aeration system piping to measure the amount of air flow and the meters’ analog or digital outputs run to the control system.

Operators of both industrial plants and wastewater facilities find that compressed air is one of the highest energy expenses. The cost of energy to produce compressed air continues to rise along with fuel costs. So, optimising the aeration process by measuring and controlling the aeration system’s air flow with a suitable flow meter reduces energy costs.

In plants with multiple aeration basins, each one is configured with several diffuser systems. Typically a wastewater treatment plant hasmultiple aeration basins and each is configured with several diffuser systems. Individual air flowmonitoring and independent control is generally required for each diffuser system. The compressor system must run 24-x-7 to maintain the optimum amount of air flowing to the diffuser systems, but demand for air changes throughout the day to accommodate a
variety of variables that affect the efficiency of the microorganisms.

Best practices for evaluating and selecting flow meters for both aeration processes and wastewater treatment applications include five key considerations:

•Flow Sensor Technology
•Accuracy and Flow Range
•Operating Environment
•Ease of Installation
•Maintenance and Life