Oil-water separators play a crucial role in compressed air systems that use oil-injected compressors. In the process of generating compressed air, these compressors also produce a condensate that contains trace amounts of oil. In order to protect the environment, the condensate must be treated – and the oil removed – before it can be disposed of.
That is where the oil-water separator comes in. Like the name says, it separates the compressor condensate’s water and oil to prevent the latter from getting into the wastewater.
Why must oil and water be separated?
This is a very important job. Most people are probably familiar with the experiment that shows how one droplet of oil quickly spreads across a large water surface. In fact, one liter of motor oil can contaminate one million liters of groundwater. An oil slick that places itself on top of a body of water can prevent oxygen from reaching the plants and animals that live in it. The oil can also harm animals by impacting the insulating characteristics of fur-bearing animals and the water-repelling properties of a bird’s feathers.
There is a second important reason why oil-containing compressor condensate must be treated: In many places, it’s the law. More and more countries and other jurisdictions are enacting increasingly stringent environmental regulations that prohibit the dumping of oil-containing water. Violating these rules may result in costly penalties.
Fortunately, as the experiment also demonstrates, oil and water don’t mix well and most of the oil will stay on the surface. Unfortunately, however, that doesn’t mean that the oil contained in compressor condensate can simply be skimmed off the top.
Instead, oil-water separation is an intricate process that leads to a cleaner environment. Let’s take a closer look at how it works.
So how does an oil-water separator work?
Naturally, there are differences between oil-water separator brands and types. However, most involve multi-stage filtration and the principle of adsorption. A first-stage filter will adsorb the free oil, while a second-stage filter will remove any remaining oil droplets and “polish” the condensate. The first filter typically consists of polypropylene fibers, which adsorb the oil, but not the water. This mean the oil will stick to the surface of the fibers. Second-stage filtration often relies on activated carbon (or organoclay for stronger emulsions) to purify the condensate.
At the end of this process, the remaining water is sufficiently free from contaminants and can be safely disposed of into the sewer system. The oil-water separator has done its job. And in the end, everybody benefits: The company that does the right thing and avoids fines and, most of all, the environment.
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