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Case Studies

The Importance of Coalescing Oil Separators: Why Oil and Water Should Never Mix

October 1 2018

Oil can get stubbornly combined with water, and without the right equipment, it is difficult to separate.

Apart from the major environmental issues that need to be addressed if oily water is discharged into the groundwater or stormwater systems, it is also illegal.

The Unauthorised Discharge Regulations 2004 of the Environmental Protection Act 1986 make it illegal to discharge substances, such as hydrocarbons, to groundwater or the stormwater system. (Pollutant Control Section 6.2 Hydrocarbon Management)

However, there is an easy way to extract oil from water and that is through the use of coalescing oil separators.


Coalescing Oil Separators use oil attracting media packs which are fixed inside the treatment chamber. The surface area on the media attracts suspended oil droplets in the wastewater and forces them to collide and form larger oil droplets.

There are significant advantages to using a coalescing oil separator. They are a simple and functional solution to remove oil and treat wastewater. It is an ideal way for small to medium enterprises to achieve water authority and environmental compliance.


Allied pumps oil-water separators (pre-treatment Products) is approved for use by the Water Corporation. These are:


The Allied Pumps’ Coalescing Plate Separator Mine Spec package combines a moulded polyethylene, fibreglass or stainless-steel chamber and high efficiency coalescing plate pack with a range of positive displacement KWIKFLO diaphragm pumps and heavy duty automotive controls.

The Allied Pumps’ CPS is an enhanced gravity separator capable of removing oils and fine solids. Typical installations would include a large silt trap or ‘bogout’ prior to the separator to handle heavy silt loadings.

The unique patented plate construction and plate material serves to multiply its efficiency in comparison with other gravity based devices. Oily water influent is either pumped or flows into the inlet chamber under gravity. The heavy solids then settle out and the 100% oil slugs rise immediately to the surface. The remaining oily water mixture flows through the plates and both the smaller oil droplets and fine solids are progressively separated. Downstream a baffle or oil dam prevents the collected oil from entering the outlet weir. Maintenance of the CPS separator is simple and can be carried out ‘in-house’.


The SPEL Puraceptor is a full retention separator that treats all flows. It is to be sized to contain more than the anticipated maximum oil spillage — enabling it to be fully operational in treating stormwater runoff at all times. It has two chambers, a coalescer and is fitted with an automatic closure device specifically designed to contain major oil spills, thereby making it suitable for high-risk applications. It achieves a water discharge quality of less than 5mg light liquids per litre, complying with European Standard BS EN 858.1. 2006. Treatable flow rates range from 2LPS to 200LPS. Pipe sizes range from 100mm to 450mm (larger sizes on request).


  • Light vehicle and heavy vehicle workshops
  • Wash bay and wash down facilities
  • Refuelling Stations
  • Any area where there is a potential for the hydrocarbons to be released into the environment

When selecting a pump for your project it is important to choose a low shear pump. These are gentle on the liquid ensuring the oil drops are bound together, rather than churned or chopped which makes the droplets smaller.

The larger the oil droplet is, the easier it is to remove.

There are a range of pumps known as ‘low shear’ pumps that are suitable for oily water. These are:

Headquarted in Western Australia with extensive stock holdings, Allied Pumps has the capacity and capability to meet all your oily water separation needs. For more information or to discuss your next project, contact a member of the team today.

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