Fine bubble diffusers

Fine bubble diffusers are a pollution control technology. They produce a plethora of very small air bubbles which rise slowly from the floor of a wastewater treatment plant or sewage treatment plant aeration tank and provide substantial and efficient mass transfer of oxygen to the water. The oxygen, combined with the food source,sewage, allows the bacteria to produce enzymes which help break down the waste so that it can settle in the secondary clarifiers or be filtered by membranes.

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The importance of achieving ever smaller bubble sizes has been a hotly debated subject in the industry as ultra fine bubbles (micrometre size) are generally perceived to rise too slowly and provide too little "pumpage" to provide adequate mixing of sewage in an aeration tank. On the other hand, the industry standard "fine bubble" with a typical discharge diameter of 2 mm is probably larger than it needs to be for many plants.

The subject of bubble size is important because the aeration system in a wastewater or sewage treatment plant consumes at least 50% and more typically 70% of the energy of the entire plant. And the more efficient the oxygen transfer, the less power the plant requires to provide the same quality of effluent water.

Furthermore, fine bubble diffusers which are evenly spread out on the floor of a tank provide the operator of the plant a great deal of flexibility in running the plant. He can create zones with high oxygen concentrations (oxic or aerobic), zones with minimal oxygen concentration (anaerobic) and zones with no oxygen (anoxic). There are different types of pollutants in wastewater, and different bacteria who thrive in different environments, so more precise targeting and removal of these is possible with the operational control that fine bubble diffusers provide, particularly with membrane diffusers.

Fine bubble diffusers have largely replaced coarse bubble diffusers and mechanical aerators in most of the developed world and in much of the developing world.

Source

• [SSI Aeration http://www.stamfordscientific.com]