[Wastewater treatment] Other air diffusers advertised as “clog-free” are anything but

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WARNING: Beware of the following when choosing an air diffuser—

Most air diffusers advertised as "non-clogging" will clog

All air diffusers encounter activated sludge counterflow

So why do air diffusers clog in the first place? Reasons include:

  1. When air is discharged into water, the high water pressure causes sludge to counterflow back into the air discharge opening(s), irrespective of the design of the air diffuser and method of diffusion. Sludge counterflow does not equal clogging.
  2. Having more than one air discharge opening causes sludge to accumulate inside, narrowing the openings and preventing sludge from flowing back out into the water.
  3. Air from the air blower (hot due to the heat of compression) dries the accumulated sludge to the point of irremovability.

As a result, air diffusers clog.

The OHR AERATOR does not clog thanks to it single large opening, which prevents sludge from accumulating by allowing it to flow readily back out into the water.

Is there a rational basis for saying ‘non-clogging air diffuser’?

While most air diffuser manufacturers advertise their products as "non-clogging", they provide neither reasons for their claim nor photos of their diffusers after an extended period of use. In particular, manufacturers of rubber porous air diffusers claim that the rubber shrinks to prevent counterflow of activated sludge. Reasonable though it may appear, this is entirely untrue; these diffusers invariably clog within a few years. For a detailed explanation of why porous air diffusers clog, please see page 16 of our air diffuser selection guide.
Air diffuser selection guide (PDF)

A single large air discharge opening is necessary to prevent clogging

There are now many vertical air diffusers on the market that feature large air discharge openings and internal structures.
Some of these diffusers have multiple openings, which causes the air to flow in branches before it is discharged. This results in uneven air distribution and sludge accumulation in narrow passageways. Hot air (exceeding 80°C in summer) then dries this sludge, clogging the unit in the same way as rubber porous air diffusers. Hence a single air discharge opening is an absolute necessity.
There are also vertical air diffusers that have dense, complicated internal structures. Unlike rubber porous air diffusers, vertical air diffusers draw in and trap matter such as MBBR bio-carriers and debris (e.g. fallen leaves or pieces of plastic). They will therefore clog if the internal structure is excessively complex.

The simple reason that the OHR AERATOR does not clog

The OHR AERATOR combines a single large air discharge opening with a simple, yet highly effective, internal structure. For more details on why and how this prevents clogging, please see page 17 of our air diffuser selection guide.
Air diffuser selection guide (PDF)

Selecting the wrong air diffuser will lead to it clogging and requiring periodic replacement. This negatively impacts wastewater treatment and lowers factory productivity. While rubber porous air diffusers are infamous for clogging, it is less well known that vertical air diffusers can also clog as they are relatively new. Please be mindful of this.