Separating Emulsified Oils in Water
Oil can become emulsified in water by mechanical agitation and by chemical emulsification or both.
Mechanical Emulsification of Oil in Water
Centrifugal pumps often will cause mechanical emulsification. Also, any influent piping that is elevated above the surface of the oily water that is splashing into the tank will also cause emulsification and possible foaming. Oil that is mechanically emulsified will usually separate given enough time. Oil coalescing grids will also assist in separating the emulsified oils.
Chemical Emulsification of Oil in Water
Degreasers and soaps can chemically emulsify oil in water. Most degreasers and industrial cleaners are high in alkalinity and will raise the pH. pH can be as high as 12 when using High Alkaline cleaners. When the pH is over 8.5 the oil in the waste water will be chemically emulsified. Gravity separation will not work at pH levels above 8.5. The pH will need to be adjusted back down to around 6.8 to 7.0. Bench scale testing is recommended to determine the best pH for removing oil that is emulsified as each waste water is going to be different. Treatment by coagulation and flocculation should also be considered.