All fuel stations, workshops and industrial yards in the UAE dump their polluted water somewhere. That water is responsible for transporting oil, grease and sediment directly to the drainage system and eventually into the environment without treatment. Precast concrete oil separators are designed to prevent this. If you need one for a project here, here’s the guide to what it does, the standards it follows, and what to look for before you select a manufacturer.
An Oil Separator’s Function
An oil separator, also known as an oil interceptor, is a precast concrete tank that is placed in the drainage line before discharge of the wastewater enters the main sewer or stormwater system. It is simply designed to remove oil, petrol and other light liquids from water before it flows downstream.
The separation is based on the physics of separation. The oil floats since it is less dense than water, and as the contaminated water slowly passes through the chamber, the oil rises to the top and is collected, while heavier sediment and grit settle to the bottom of the chamber. The clean water separates from the top layer and the oil is left behind and the sludge is collected in the bottom.
In What Ways Are These Used?
Oil separators are found wherever water may come into contact with fuel, oil, or grease prior to entering a drainage system. That includes fuel outlets receiving deliveries of fuel by tanker and forecourt runoff, vehicle parking and workshop areas where vehicles leak onto the floor, which then gets washed away, industrial plants that process fluids that might contaminate the wastewater, and vehicle wash bays where oil and sediment washes off all the time.
The flows, contamination levels and characteristics of each of these applications vary and that’s precisely why the sizing of separators isn’t a one-size-fits-all affair.
Class 2 vs Class 1: Why This Separation Is Important
Not all oil separators are created with the same capacity and that’s where many buyers go wrong. Separators are classified into two classes of performance under the European standard EN 858, that covers light liquids, such as oil and petrol.
Class 1 separators are engineered to get below 5 mg/l of oil, at standard test conditions. They are normally needed wherever treated water is discharged to surface water drains or the natural environment because they are a more stringent limit that helps protect water bodies from being contaminated.
Class 2 separators can be used to discharge into a lower concentration and typically are used for less sensitive discharges, such as connection to a municipal sewer system instead of open water. Where is the treated water going to end up after treatment should have an impact on the type of separator you choose on day one, not after installation.
Full Retention vs Bypass Separators Precast Concrete Oil Separator Manufacturer in UAE
Separators vary not just by class rating, but also in their management of flow volume. Full retention separators process all of the flow that is sent through the drainage system, even small amounts of water.
Bypass separators are different. They enable a higher flow than the maximum allowable flow to pass through the treatment chamber completely when there is heavy flow so that the system treats the peak flow that it was designed for. The right option is determined by your site’s drainage capacity, the amount of rain your site is exposed to and the frequency of high flows.
The Most Important Design Elements to Be Familiar With
A well designed precast concrete oil separator is comprised of a number of parts and understanding the parts involved helps you to more readily assess the product from a manufacturer than just by taking their word on a brochure.
- Sludge trap. The majority of separator systems have a separate sludge trap or sediment bucket that is designed to catch any heavier solids that do not interfere with the oil separation process. This component requires regular cleaning and therefore access is as important as capacity.
- Coalescing media. Coalescing plates or media are sometimes incorporated into some separator designs to facilitate the removal of smaller oil droplets into larger ones, which accelerates separator separation and overall treatment efficiency. Retrofitting or including this as an option in the manufacturer’s product line, depending on changes in regulations later, means more long-term flexibility for the buyer.
- Automatic closure devices. Some separator designs feature a built in shut-off system which stops flow when oil storage capacity is reached, to prevent untreated oil from entering the drain system. This feature may or may not be necessary for a particular application and may or may not be a local regulatory requirement.
- Access covers. Access covers must be installed correctly and be rated for the traffic loads above them, and should be inspected and cleaned regularly. Heavy duty covers are necessary for the separators used in vehicle traffic areas; a regular cover underneath a driveway is a bad idea that will be evident the next time a truck runs over it.
- Watertight construction. The requirement for watertightness of components comes into play throughout the design process with regard to the separator, because its purpose is lost if it leaks.
Why Precast Concrete Is the Standard Material Choice
While it’s technically possible to create an oil separator from a number of materials, no other material is used so widely as precast concrete. It provides structural strength to withstand loads placed on it when buried and above ground, it is immune to the corrosive effects of oil and hydrocarbon exposure over time, and it comes ready to install (no formwork and curing needed on site).
In the UAE the concern of buoyancy and burden of burial becomes a real engineering problem, particularly when separators are located near coastal areas or in high groundwater regions. Well-designed precast tank takes these conditions directly into its structural specification and does not treat them as an ‘after-thought’.
When Purchasing an Oil Separator, It Is Important to Ask the Manufacturer Specific Questions
A few direct questions lie between a manufacturer that truly engineers these systems and a manufacturer that is just selling off the shelf tanks.
- What is their product classified under in EN 858? Request a specific class rating and preferably documentation that the product has been tested to that rating. If the answer is too vague here, it’s a red flag.
- Do they have both full retention as well as bypass options? The type that fits depends on the drainage of your site. If a manufacturer only has one configuration, they might be directing you to sell what they have on hand instead of what you require.
- Do they have the ability to design the separator for your specific flow? This is not a matter of just picking a separator size from a size chart; rather, the capacity of the separator should be determined by the flow and contamination load at your site.
- Do they include sludge traps and coalescing media as standard, or as an add-on? It saves you from unpleasant surprises down the road when you don’t use the features that come with the purchase of the product.
- Do they have access covers that can be supplied for installations under driveways or parking areas, for traffic? This detail will make a difference if your separator is located anywhere even close to vehicle traffic and this is no longer an afterthought.
- How have they fared in projects that are installed on the high ground or coastal locations? The conditions in the UAE are quite different from place to place and the buoyancy protection of buried tanks in high-ground water areas is different and cannot be a standard design for all areas.
Most Errors Are Common to All Precast Concrete Oil Separator Manufacturer in UAE
There are some common problems on the oil separator project throughout the region. A Class 2 separator is a major compliance blunder at a facility that has openings in an open water body, and can result in rework expenses if regulators catch it. A common mistake is to install a standard duty access cover under an area that will be used for vehicles after a short period of time, resulting in cracked covers after a short while.
The most common error is sizing the separator on estimate rather than calculation and the outcome is a separator that may overflow during its peak use or may be unnecessarily large for a site with never required such a large amount of capacity.
Bringing It Together Precast Concrete Oil Separator Manufacturer in UAE
Precast concrete oil separators are extremely quiet components of environmental infrastructure, and if they are installed properly, they will benefit your compliance record and the environment. Consider the manufacturer’s ability to explain EN 858 class ratings regarding size, your site conditions, and the ability to provide real structural and watertightness explanations, but not a sales pitch. If it is done properly, the separator will do its job silently for years, which is a good thing for infrastructure.
