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Tech Showcase | Oil/Liquid separators

Optional polluted puddle 1

Marsh Industries technical sales director Stephen Le Tissier questions whether the current testing regime within European Standard BS EN 858 still provides an acceptable level of pollutant after separation.

The most common form of separation technology is a vessel designed to separate contaminants by gravity to a specific standard of discharge.

 These systems are typically used in surface water drainage systems for car parks, petrol station forecourts and other “at risk” locations.

Vessel design is calculated from the volume, flow rate of combined water, and the contaminant to ensure sufficient retention time for gravity separation to occur. “Forced flow” separation can also be achieved by adding a coalescing device within the vessel.

Between 1970 and 2000, separator technology evolved from three chamber designs to include bypass flow designs with additional components such as coalescing filters, automatic closure devices, alarms as well as contaminant  recovery/removal systems allowing for recycling of light liquids.

Current EN standard

The European Standard, BS EN 858 parts 1&2, was introduced in 2002 to normalise design and regulate testing of products across Europe. This standard settled on a two tier quality level – class 1 and class 2.

  • Class 1 – designed to achieve a discharge concentration of less than 5mg/l of oil in the discharge
  • Class 2 – designed to achieve a discharge concentration of less than 100mg/l of oil in the discharge

Once testing is complete and approval achieved, manufacturers are free to bring their products to market.

The effects of current standards

A good starting point for any product is to set out relevant standards and levels of quality in product build and product performance. However, since the introduction of BS EN 858 in 2002, product development in gravity oil/liquid separation has remained static.

Screen shot 2018 09 20 at 14.39.50

Screen shot 2018 09 20 at 14.39.50

Manufacturers are only required to meet the testing standards to sell product. There has been no natural drive to improve product performance.

The current class 1 standard of less than 5mg/l of light liquid is only determined by test conditions. Marsh Industries’ experience in this field indicates that this standard is rarely met once a product is installed.

The reality of current standards

With the current level of 5mg/l for a Class 1 discharge – the question is: “Are Class 1 separators the very best that manufacturers can offer?”

Studies have shown that the majority of hydrocarbon pollutants entering the water system stems from urban developments.

Leaving aside the toxic effects of contaminants on human and aquatic life, when a hydrocarbon molecule spreads to one molecule thick and given enough surface area to spread, five litres of oil would be more than enough to contaminate five football pitches.

Screen shot 2018 09 20 at 14.41.24

Screen shot 2018 09 20 at 14.41.24

In addition, most hydrocarbon molecules are attached to silt particles; where Stokes law proves that these particles will sink rather than float as conventional separators require.

When mixed with other elements in real life scenarios, such as glycol, standard gravity separators become less efficient at contaminate removal.

Marsh Industries believes that the current testing standards covering products within the gravity separator market are outmoded and fail to protect the environment as they should. They do not reflect or address any “real-life” scenario where hydrocarbon pollution is prevalent.

The solution

Marsh Industries has developed the Portapura,  an innovative separator system that breaks the constraints of the current standards.

The Portapura takes advantage of nanofiltration technology to produce discharge that is 50 times better than the EN standard; that is less than 0.1mg/l – the standard only requires less than 5mg/l for a “class 1 discharge”.

Testing was analysed for hydrocarbon content using infrared spectroscopy at Geotaix Umwelttechnologie.


Screen shot 2018 09 20 at 14.46.48

Screen shot 2018 09 20 at 14.46.48

During the sampling period, five samples of 500ml were taken via the sampling point.

The quality of discharge from the Portapura exceeded the measurable level of the test equipment not to mention the current EN standard.

Full testing is now complete for the entire Portapura separator range and the products are undergoing their “release to sale” process.

  • Produced in association with Marsh Industries

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