How to Construct an Oil Water Separator

Understanding that most petroleum oils and fat and grease are less dense than water is the starting point for designing an oil water separator (OWS) or its cousin, the FOG (Food- Oil- Grease) separator. By leveraging this principle, these effective water treatment devices can effectively separate oil and grease from wastewater, ensuring that the water discharged back into the environment is clean and safe.

Basic Principles of Oil Water Separation

The initial inflow of water and contaminants enters a chamber that is positioned relatively high and is vented to the atmosphere. This chamber includes a solid downstream baffle that seals around the top and sides but remains open at the bottom. The important aspect of this design is that the bottom opening allows the heavier and more dense water to pass through while the lighter and less dense oil and grease materials remain floating on top.

The chambers are intentionally sized to facilitate cleaning, either through physical access or to ensure low water velocity. Low water velocity enables natural separation with minimal turbulence, allowing pollutants to rise to the top. The chambers are often equipped with a test and observation port, as well as an instrumentation port for installing sensors to monitor the presence of hydrocarbons. Many OWS are designed to protect against unlikely gasoline or oil spills in areas like parking lots or garages, while others are built to handle regular FOG from food preparation.

Enhanced Separation through Multichamber Design

For situations requiring a higher degree of cleaning, additional chambers can be added after the initial one. Each subsequent chamber performs the same function of separating contaminants from the water. These chambers also have removable access ports for cleaning the accumulated contaminants. They are vented separately to seal against sewer gases and to allow outflow by breaking any vacuum created by the outflow.

The final chamber ensures that the outflow is low, maintaining a sufficient volume of water to keep the contaminants floating. This design can effectively treat wastewater, making it suitable for various applications in both industrial and commercial settings.

Manufacturing and Standards Compliance

These devices are manufactured by several companies and are rated by various standards agencies and governmental approvals depending on their jurisdiction of final use. While it is possible to design your own separator, there is little benefit to doing so unless there is a specific need that is not met by existing manufactured options. Understanding the principles behind these devices is crucial for making informed decisions and ensuring compliance.

Disclaimer: The information provided above is a general response to the nature of the question and no specific application details should be implied or inferred from this response. The information does not constitute legal or professional engineering advice, and seeking the advice of a qualified professional specific to your application is always recommended.