Fine bubble diffusers are a

pollution control Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...

technology used to aerate wastewater for

sewage treatment Sewage treatment (or domestic wastewater treatment, municipal wastewater treatment) is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable for discharge to the surrounding envir ...

Description

Fine bubble diffusers 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 Sewage (or domestic sewage, domestic wastewater, municipal wastewater) is a type of wastewater that is produced by a community of people. It is typically transported through a sewer system. Sewage consists of wastewater discharged from residenc ...

, 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. A fine bubble diffuser is commonly manufactured in various forms: tube, disc, plate, and dome.

Bubble size

The subject of bubble size is important because the aeration system in a wastewater or sewage treatment plant consumes an average of 50 to 70 percent of the energy of the entire plant. Increasing the oxygen transfer efficiency decreases the power the plant requires to provide the same quality of

effluent Effluent is wastewater from sewers or industrial outfalls that flows directly into surface waters either untreated or after being treated at a facility. The term has slightly different meanings in certain contexts, and may contain various pollut ...

water. Furthermore, fine bubble diffusers evenly spread out (often referred to as a 'grid arrangement') on the floor of a tank, provide the operator of the plant a great deal of operational flexibility. This can be used to create zones with high oxygen concentrations (oxic or

aerobic Aerobic means "requiring air," in which "air" usually means oxygen. Aerobic may also refer to * Aerobic exercise, prolonged exercise of moderate intensity * Aerobics, a form of aerobic exercise * Aerobic respiration, the aerobic process of cellu ...

), zones with minimal oxygen concentration (

anoxic The term anoxia means a total depletion in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms anoxia and hypoxia are used in various contexts: * Anoxic waters, sea water, fresh water or groundwater that are depleted of diss ...

) and zones with no oxygen (anaerobic). This allows for more precise targeting and removal of specific contaminants. 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. Average bubble diameters of 0.9 mm are possible nowadays, using special polyurethane (PUR) or special recently developed EPDM membranes. Fine bubble diffusers have largely replaced

coarse bubble diffusers Coarse bubble diffusers are a pollution control technology used to aerate and or mix wastewater for sewage treatment. Description Coarse bubble diffusers produce 1/4 to 1/2 inch (6.4 to 13 mm) bubbles which rise rapidly from the floor ...

and mechanical aerators in most of the developed world and in much of the developing world. The exception would be in secondary treatment phases, such as activated sludge processing tanks, where 85 to 90 percent of any remaining solid materials (floating on the surface) are removed through settling or biological processes. The biological process uses air to encourage bacterial growth that would consume many of these waste materials, such as phosphorus and nitrogen that are dissolved in the wastewater. The larger air release openings of a coarse bubble diffuser helps to facilitate a higher oxygen transfer rate and bacterial growth. One disadvantage of using fine bubble diffusers in activated sludge tanks is the tendency of floc (particle) clogging the small air release holes.

References

{{DEFAULTSORT:Fine Bubble Diffusers Sewerage Water treatment Environmental engineering Water technology

Description

Bubble size

See also

References