There are a vast number of stormwater separators on the market which can make it challenging when selecting the ideal solution for each project.  Hydrodynamic separators and oil/water separators are often used interchangeably in the industry but each system is unique and one may be better suited for the overall treatment goals of the project.   So what is the difference between a hydrodynamic separator and an oil water separator and how can you determine which one is best suited for your project?

A hydrodynamic separator (HDS) such as the CDS, Vortechs or VortSentry is a system that incorporates internal components that promote swirling of the stormwater.  By swirling the stormwater within the system you are able to concentrate solids into a low velocity vortex and enhance particle settling.  Many systems also incorporate oil baffles and/or screens which allow for effective oil, trash and debris removal.  When it comes to oil removal though, an HDS system will be limited on the capacity of storage as the oil storage volume is restricted to the volume of the oil baffle within the system. 

An oil/water separator such as the VortClarex is a system that utilizes coalescing media to efficiently remove freely dispersed oil and other liquid pollutants from urban runoff and industrial discharges.  It specifically targets oil and grease and is designed for sites where these pollutants is of the greatest concern or where oil and grease effluent targets are specified.  Many oil/water separators can also meet Spill Prevention, Control and Counter Measure (SPCC) requirements.  You’ll also see several Oil/Water separators that incorporate a solids baffle wall which allows for some sediment capture within the system.

If HDS systems and Oil/Water separators capture the same types of pollutants, how can you determine which is ideal for your project goals?   It’s true that both systems can capture the same pollutants, but each system is going to be more efficient at capturing one than the other.  For instance, if your main goal is to capture solids and/or trash and you would also like to provide removal of the small volume of oil and grease that may be present in the stormwater, a Hydrodynamic Separator is the better choice.  If the main pollutant of concern is oil and grease or petroleum products such as gasoline, diesel and jet fuel, an oil water separator is likely the better choice.