Oil and Water are two liquid phases that are difficult to combine. Normally contamination from Oil into Water results in a liquid oily phase that floats on the top of the water and with very small amounts can spread and looks unsightly. Whilst this type of phase separation looks unsightly it is not too difficult to separate. By far more difficult are water & oil emulsions, which nowadays are normally bound together with some form of polymer, and look like a milky liquid.
Cooling and lubrication oils are generally used to cool metal cutting equipment. Normally they are in a closed loop system with a strainer to collect the waste metals before recycling the oil. However, in most applications some oil is lost during production, or wash-down periods. In addition, these applications also generally tend to have water as a carrier, and assist in the cooling process. However, the water used in these applications should be treated, if not the natural water salts can react with the other mediums and cause oxidation within the process. This oxidation generally tends to express itself by accelerating wear on the machinery being used, it can also result in pitting on the metal, which in the final product will show itself as blotches on the metal surface.
Some other industries such as soaps, shaving gels & foams and the detergents industries, use oil based antifoams to suppress the foam that is generated during manufacture. Whilst very useful in this application the vegetable oil in the antifoam does carry through and will separate out in the wastewater treatment process. Therefore, the process would be to treat at source, so that the oil is taken out and the clean water can be recycled.
In the food industry, oils are used either as ingredients or in the preparation of food products. The oils from these processes, which are generally light vegetable oils, can pass through some physical treatment systems such as Dissolved Air Floatation systems (DAF) and end up in the wastewater treatment plant. In addition, in some food process’s emulsifiers are used to ensure the oil mixes into the water phase this then proves to be extremely difficult to remove in the wastewater treatment process.
United International Hydo Engineering is able to offer a range of systems to assist in the separation of oil in contaminated water, links to the processes are highlighted below.
However, it is important to remember that not just one system might be required in some sectors such as Food & Beverage a number of chemical and physical processes might be required, depending on the level and types of oil in the wastewater and the eventual requirement for the treated wastewater.
In certain cases, due to the calorific value of the oil, once separated and recovered there exists opportunities for this to be sold or used in areas such as Boiler Feedstock. Treated water from the separation can be reused in areas such as Cooling Towers and Boilers or with additional treatment back into production areas.
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