Oil in Water Emulsions When technologies for the treatment of oily waters are selected, the nature of the water to be treated must be taken into account, and not only observe the typical parameters such as oil concentration, degrees API, specific gravity, temperature, etc. The lighter a hydrocarbon is, we might tend to think that it is easier to separate it from water, however this is not always the case. Light hydrocarbons such as gasoline have lower viscosities and surface tensions than a light crude, so they are more sensitive to formation of mechanical or chemical emulsions in the presence of an emulsifying agent. Treatment techniques should be carefully evaluated, and tested in the field, since the oil removal efficiency of a separation equipment will depend on the stability of the oil droplet in the presence of a turbulent medium. When configuring an oily water treatment system, special attention should be given to the way in which we store and transfer oily contaminated water. Physical-Chemical treatment plays a key role in the treatment of emulsions but sometimes might result too expensive. It is important to incorporate an evaluation of CAPEX/OPEX and NPV comparing different options when making such kind of investments.