The difference between water treatment defoamers and polyether defoamers

1. Different Core Components and Mechanisms of Action

Polyether Defoamers: The main component is a block copolymer of ethylene oxide (EO) and propylene oxide (PO). It utilizes the penetration and spreading of polyether segments on the foam film to reduce surface tension, causing the foam to break down. 

Its characteristic is strong foam suppression ability (it can prevent foam regeneration for a long time).

Other Water Treatment Defoamers (usually referring to silicone-based defoamers): The main components are polydimethylsiloxane (silicone oil) and hydrophobic silica. It rapidly destroys existing foam through extremely low surface tension. 

Its characteristic is a fast defoaming speed, but short foam suppression time.

2. Comparison Table: Polyether vs. Silicone Defoamers

3. Typical Application Scenarios in Water Treatment

3.1 Scenarios where polyether defoamers are preferred:

• MBR (Membrane Bioreactor): This is the most critical difference. Polyethers must be used because silicones will permanently foul the membrane, causing significant losses.

• Aerobic Aeration Tanks/Biochemical Systems: Polyethers are microbial-friendly and have strong, sustained foam-suppressing ability, preventing repeated foam generation.High-Temperature or Strongly Acidic/Alkaline Wastewater: Such as wastewater from dyeing, chemical, and steel mills.

• High Requirements for Effluent Quality: Polyether residues will not cause oil floating (silicone spots) in the water.

3.2 Scenarios where silicone defoamers are preferred:

• Rapidly Eliminating Large Amounts of Foam: Such as when a large amount of foam instantly accumulates on the surface of a sedimentation tank, requiring immediate suppression.

• Pretreatment or Physicochemical Stages of Membrane-Free Processes: Such as equalization tanks, coagulation tanks, and dissolved air flotation tanks (non-membrane post-treatment).

• Extremely Cost-Sensitive: Silicones are typically 20-40% cheaper than polyethers.

4. Summary: One-sentence advice:

• If you are using MBR technology or have a biological treatment tank or membrane system, you must choose a polyether defoamer. Silicone-based defoamers will have disastrous consequences.

• If it is just ordinary physical and chemical treatment (without a membrane), and the foam volume is extremely high and needs to be eliminated quickly: silicone defoamers are more efficient and cheaper.

• If the wastewater temperature is high (>60℃) or the pH is extreme (<4 or >10): polyether is the preferred choice.

In actual water treatment, many compound products contain both polyether and a small amount of organosilicon to achieve both rapid defoaming and long-lasting foam suppression. However, the composition must be carefully confirmed before using a membrane system.