Bubble Diffuser Differences
Choosing between fine bubble diffusers and coarse bubble diffusers has often been difficult because each holds distinct benefits over the other. Fine pores typically release bubbles with a diameter between 0 – 3 mm, while coarse bubble diffusers release bubbles with a diameter ranging from 3 – 50 mm.
Diffusers versus Holey Pipes
There are several reasons why you should use diffusers instead of simply drilling holes in a length of pipe:
While drilling holes in pipes seems like a simple, pragmatic option, diffusers are designed to help keep the contents of your tank from entering your air supply lines and prevent clogging when the blower is not operating. The membranes on coarse and fine bubble diffusers contract and serve as a check valve when air pressure is not applied internally.
AIR FLOW CONTROL
Diffusers help balance air flow because the airflow from an engineered diffuser is both predictable and consistent from one to the next. Calculating actual airflow from a length of pipe with drilled holes would be a wild guess at best, and equalizing air discharge over the full length cannot be assured.
Large numbers of small bubbles will transfer far more oxygen than a small number of large bubbles due to the increase in total bubble surface area. Diffusers generate smaller bubbles than those coming from holes drilled in pipe. Therefore, when using diffusers you can achieve a desired amount of oxygen transfer with less air (less energy demand). This means lower blower operating speeds and lower energy costs. This is especially true if you incorporate smaller bubble diffusers into your system.
Fine Bubble vs Coarse Bubble Diffusers
When comparing fine and coarse bubble diffusers, the majority fail to withstand specific challenges. Besides not lasting beyond 1 or 2 years, most will clog, blow off or crack. Any bubble diffuser that eliminates these problems would deliver a huge cost-savings, not only in product replacement costs, but in system downtime needed for their cleaning or exchange.
Fine Bubble Diffusers
Fine bubble diffusion introduces very small bubbles into a wastewater treatment process. The main principle behind using fine bubble diffusers versus coarse bubble diffusers is that smaller bubbles result in more bubble surface area per unit volume and greater oxygen transfer exchange. Fine bubble sizes range from 0 to 3 mm.
Advantages and Disadvantages of Fine Bubble Diffusers
FINE BUBBLE ADVANTAGES
- High aeration efficiency
- High oxygen transfer efficiency
- Require less energy to run (compared to coarse bubble diffusers)
- Easily adapt to existing basins (for replacements or upgrades)
- Lower volatile organic compound emissions (compared to coarse diffusers or mechanical aeration devices)
- Satisfy high oxygen demands
FINE BUBBLE DISADVANTAGES
- Susceptible to chemical or biological fouling — leading to impaired oxygen transfer / aeration inefficiency)*
- * More expensive — fine pore diffusers require more routine cleaning and replacement (plus additional costs of maintenance and downtime)
- Energy cost challenges — when fine pores become clogged, the diffusers may require more energy to operate (than coarse diffusers)
- Air Flow distribution is critical for fine diffuser performance. This requires proper selection of Air Flow Control Systems to ensure fine pore diffusers function at peak efficiency levels
- Conflicting air flow requirements — Aeration tanks may have conflicting needs of air flow: mixing versus oxygen transfer
Coarse Bubble Diffusers
Coarse bubble diffusers offer affordable and durable mixing and aeration. They are ideal for situations that combine airflow mixing and oxygen introduction, and especially in wastewater with high-solids content. Coarse bubble sizes range from 3 to 50 mm*.
Advantages and Disadvantages of Coarse Bubble Diffusers
COARSE BUBBLE ADVANTAGES
- Less prone to plugging due to air mass coming from the larger hole openings
- Optimal mixing capacity in tanks with thicker mass and sediments
- Ideal solution for secondary treatment phase. (If fine bubble diffusers were used in this secondary phase, floc, sediment and carbonate build-up would narrow or plug its smaller air holes.)
COARSE BUBBLE DISADVANTAGES
- Consume more energy to operate
- Less efficient oxygen transfer
- Less contact time — because larger bubbles will ascend more quickly through the wastewater than smaller bubbles
* WHAT IF… there was a diffuser that offered the advantages of both the Fine Bubble and Coarse Bubble diffusers?
Well, there is such a diffuser. The Flexcap Coarse Bubble Diffuser can make these claims because it releases bubbles in a “medium size” range: 3 – 5 mm. Learn about Flexcap Diffuser.