There are many industrial and commercial processes that create foam, either by mechanical agitation or through a chemically influenced mechanism. This foam can cause significant problems if left untreated. There are two main methods used to treat the build-up of foam: antifoams and defoamers.
In this article, we explore what foam is, how it occurs and the issues it can cause, before highlighting how antifoams and defoamers are used.
This is the third article in our series about the roles different wastewater treatment chemicals play in the industrial water treatment process; make sure to read our other articles about the role of flocculants and the role of coagulants to learn more about these important chemicals.
What is foam?
Foam is a mass of bubbles that’s created when certain types of gas are dispersed into a liquid, which then stabilise. Foam cannot be formed in pure water, even with strong aeration, as there is nothing present in the water to stabilise it. Water must contain certain additional components, either soluble or insoluble, to form stable foam.
Types of foam
There are two main types of foam, biological foam and surfactant foam:
- Biological foam is caused by the activity of microorganisms as they metabolise and break down organic matter in wastewater. Bio-foam is comprised of very small circular bubbles, and is extremely stable and can appear dry.
- Surfactant foam is caused by the introduction of surface-active agents like soaps and detergents, or by reactions between caustics and oil or grease, and other chemical discharge.
How do these foams occur?
Biological foams can be caused by protein materials not biodegrading, by certain filamentous bacteria producing extracellular polymer (ECP) substances that are active on the surface, or in long sludge age systems that are operating on high nitrogen raw wastewaters without sufficient denitrification facilities.
Surfactants contain a water repelling (hydrophobic) section and a water attracting (hydrophilic) section. These surfactant molecules form a thin film (a.k.a. a monomolecular layer) on the surface of the water, where it meets the air. This layer is the essential precondition for the formation of stable foams; it surrounds bubbles to create a stable foam lamella, which will continue to grow while gas is escaping into the liquid, or it is counteracted.
What issues can foam cause?
Foam can cause problems with industrial equipment and processes, and impact overall plant efficiency; reducing throughput and causing overspills. These overspills can become a slip hazard on commercial sites, which could lead to personal injury and other accidents; and cleaning up said spills can be time-consuming and labour intensive.
What are antifoams?
Antifoams are chemical agents designed to control the wasteful formation of foam during industrial processes. They come in many different forms including mineral oil, silicone, natural organic and synthetic organic, and the appropriate kinds will depend on the type of foam that needs to be prevented.
What is the difference between antifoams and defoamers?
While the terms antifoam and defoamer are often used interchangeably, they actually perform different functions. Antifoaming agents are added before foam starts to form, ideally at a stage just beforehand, like before the addition of surfactants; and they actively prevent the build-up of foam. Defoamers, on the other hand, are added to liquids with foam that’s already formed, and they break down the foam to prevent tanks or containers overflowing.
How do antifoams work?
Antifoams work by changing the characteristics of the liquid to prevent foam building up. Antifoams displace the surfactant molecules in the foam lamella, meaning the monomolecular layers are less elastic ad break down more easily. Combined antifoam and defoaming agents may also contain solid particles like waxes, paraffin or silicas, which disperse onto the foam lamella and cause the bubbles to burst, allowing the trapped air to escape and preventing the continued build-up of the foam.
Operating temperatures of the foaming solution:
The operating temperature of the foaming solution is a key consideration. Cloud point is the temperature above which an aqueous solution of a water-soluble surfactant becomes turbid. Knowing the cloud point is very important. Foam control products applied at operating temperatures outside the cloud point of the product can actually worsen the situation by causing more foam. The cloud point of the product should be just below the application temperature. For example, if the cloud point of a foam control product is 23°C, the defoamer should be used around 25-28°C for maximum efficacy.
Foam can cause disruption to many industrial and commercial operations, and if left untreated, could cause dangerous overspills that may lead to an accident on-site, as well as significant downtime while the spill is cleaned up. Enva are experts in chemical products for wastewater treatment, so you can rely on our expert team to help you keep your wastewater foam-free. To find out more about how Enva can help with foam prevention and treatment, or any other element of waste water treatment, visit our website.
To discuss your needs in more detail, please contact Enva today, our team of experts will be happy to help tailor a solution to your specific requirements.
