Treating Oily Wastewater

Treaty Oily Wastewater

Types of oily wastewater

Many types of wastewater contain oil. Water based coolants, compressor condensate, as well as any wash waters that were used to rinse oily items are a few examples. Although a typical wastewater evaporator cannot process oil itself, as oil evaporates at a much higher temperature, this type of waste stream can be easily and effectively handled with an ENCON evaporation system.

The oil is typically found as either a free oil (a distinct oil layer) or as emulsified oil (suspended homogeneously in solution).


  • Free oil
    Typical examples of this type of waste stream include water-based coolants, die cast solutions and compressor condensate. In most cases, the oil layer floats on top of the wastewater, although in rare instances it sinks below the wastewater. The typical way to handle this type of waste stream is to feed the evaporator from below the floating oil layer in the holding tank (or above in cases of sinking oil). This is done to minimize the amount of free oil in the evaporator and therefore the frequency of decanting.

    Although ENCON Evaporators can accept limited amounts of free oil, it is not beneficial to heat the free oil. This is because oil generally evaporates at higher temperatures than water and at  higher temperature than the evaporator is designed for.  Heating oil in an evaporator is a waste of energy.

    If enough free oil builds up in the evaporator, the boiling temperature will elevate rapidly, which will cause the evaporator to shut down prematurely. At this point the free oil needs to be decanted from the evaporator. The oil can either be decanted manually or with the optional auto decant system.

    ...this type of waste stream can be easily and effectively handled with an ENCON evaporation system...
  • Emulsified oils
    Water-based coolants and parts wash waters are typical examples of waste streams with emulsified oils. Both of these examples can have emulsified and free floating oils simultaneously.

    The emulsified oils will typically "break" from the wastewater solution once the temperature rises sufficiently, generally around 160F.  Since there is a vigorous boil in the evaporator tank, the oil will appear to stay in solution. Upon cooling however, the now free oil will float to the surface and will need to be decanted periodically from the system.

Decanting oil from a Thermal Evaporator

If over 2" of free oil float on top of the wastewater in the evaporator tank, it is time to decant the oil from the evaporator. This process can be done manually or with the auto decant option.

How can I tell if my wastewater is a good candidate for evaporation?

The centerpiece of our consultative approach is the wastewater qualification process. Not all waste streams are good candidates for evaporation. We believe it’s better to find that out in our laboratory than on your factory floor.

This free analysis determines how appropriate the waste stream is for evaporation and how it will function in the ENCON evaporator. This analysis also helps determine materials of construction and allows us to determine operating procedure recommendations. If more detailed analysis of specific parameters is needed, ENCON can prepare appropriate samples and send them for outside lab analysis for a nominal cost (prices for analytical tests vary).

Once the analysis is complete, your Sales Engineer will deliver a report detailing the results to you. This report includes material of construction and pH adjustment recommendations, if needed. This allows you to make an informed decision if an ENCON evaporator is right for you.

I'd like to find out more. What is the next step?

Use the quick question form on the left, or call us at (603) 624-5110.

It all starts with your initial conversation with an ENCON Sales Engineer. These experts take the time to truly understand your needs and your own unique wastewater challenges. Their thorough knowledge of the wastewater industry in general and evaporation technology in particular allows them to manage ENCON’s resources toward addressing your unique wastewater disposal project.

They’ll get to know the processes in your plant that generate wastewater. How you currently deal with it. Even what processes you might implement in the future that may affect the volume and quality of your wastewater. This allows them to help you select the right evaporator for today and tomorrow.