The most commonly used oily water treatment systems use gravity to separate water from oil and solids. They are based on the principle of coalescence. Coalescers bind smaller and minuscule droplets of oil into oil droplets, which then rise faster in accordance with Stokes‘ law. Coalescing elements, on the surface of which the finest oil droplets settle, promote the coalescence of smaller droplets and ensure that the oil-water emulsion separates into coherent phases more quickly and completely. As a result, the lighter oil collects on the surface, while the cleaned water remains in the lower part of the oil separator tank, where it can be drained off and pumped through a second oil separator stage for fine filtration. In this second filter stage, emulsions are separated by activated carbon filters and hydrocarbons still present in the water are bound. Through this process, concentrations well below 5 ppm can be achieved. The particles adhere to the filter cartridges. Over a period of time, depending on the degree of contamination, the activated carbon filters become saturated.
Before discharge overboard, a sensor measures whether the pre-set maximum concentration of e.g. 15 ppm residual oil content has been reached by this treatment. If it is still higher than this, the mixture is usually pumped back into the bilge water tank. The OWS-COM is equipped with an oil content measuring unit, which takes measurements before and after the second oil separation stage.
If the first stage of the coalescence process has already reached the desired target, the treated water is discharged directly from the ship without passing through the second filter stage. This approach extends the service life of the activated carbon filter cartridges, and reduces the energy used.
Key Features & Benefits
- Suction type separator: Less turbulence results in more efficient oil-water separation compared to other technologies
- Extremely compact: suitable for newsbuilds and retrofit
- Easy to install and maintain
- Extremely economical: regular water checks ensure that a second stage of separation is bypassed whenever possible
Extremely safe: Oil Monitoring device activates recirculation mode if required