Aeration systems installed at wastewater treatment works include an intricate labyrinth of pipes and diffusers, hidden metres below the ground. The diffusers create tiny bubbles that rise to the surface of the water, breaking down solids and oxygenating the sludge. But everything has a shelf life.
Both diffuser membranes and couplings have an efficient lifespan of between 8 and 10 years – but some systems are still running after 20 years. However, they will not be working efficiently. You would expect a return on your investment after eight years through energy savings by replacing the diffuser membranes thus bringing them back to an ‘as new’ condition.
The first sign of diffusers deteriorating can be witnessed in an increase in energy. This is because aged membranes create bigger bubbles which are less effective. That’s the ‘canary’ that something is wrong – but unless energy consumption levels are being monitored closely and regularly this early warning sign often goes unnoticed.
The number of diffusers will depend on the dimensions of the plant, but eventually the rubber will perish over time. This increases the pressure within the system which in turn increases energy use.
In a fully working aeration tank, you would expect to see bubbles breaking out gently on the surface of the water, but on a failing system you might see one or more large bubbles erupting violently on the surface.
I have worked in this industry for almost 20 years, and speaking from experience, the higher energy consumption and erupting bubbles are normally overlooked until the equipment fails and physically stops working. Thankfully, most of the common problems linked to a failing aeration system don’t stop the process from working. It will simply limp on until something has to be done.
If the membranes or couplings have split, water and sewage will make their way inside the air pipes and block the diffusers from the inside causing the plant to cease functioning.
It is imperative to have a succession plan for each plant, planning and budgeting for upgrades at necessary intervals to minimise downtime.
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