Industrial Waste Water Treatment – Phase 1

The industrial waste water treatment is separated into 3 main phases, each phase being more or less advanced and complex depending on the nature of the effluent to be treated and the discharge standard in force.

Phase 1 is the physicochemical process with its filtration and sedimentation steps, the solid and oil removal if needed.

Similar to drinking water preparation the waste water would go through settling and filtration:


– Fine screening: the water is filtered first through a screen to catch the biggest particles, then through a fine-mesh sieve to trap smaller ones.

– Flocculation and settling: a coagulant (chemical product) is mixed with the water to cause the remaining waste—dust, dirt particles, etc.—to clump together. These flocculates sink to the bottom of the settling tank. Around 90% of suspended solids (SS) are removed during this operation.


Depending on the nature of the effluent and the amount of oil in the wastewater one of two technologies can be used:

Dissolved Air Flotation Separator

A Dissolved Air Flotation (DAF) separator is an oil/water separator, which is used for the removal of suspended solids and emulsified oil from liquids. To remove the emulsified oil, the emulsion is first broken by the addition of chemicals. For this, the additional flash mixer and flocculation units are provided upstream of the dissolved air flotation tank. Flotation of solids is achieved by the introduction of millions of microscopic bubbles into the process water.

Source: Water Treatment Plant

American Petroleum Institute Separator

An API Separator is a gravity separation device, which is used to separate oil and water. The equipment is designed using Stokes Law to define the rise velocity of oil droplets based on their size and density. API separators are frequently used for the treatment of refinery wastewater, which has been contaminated by oil and oil-bearing sludge. These oil/water separators are based on the difference in specific gravity to allow heavier liquids to settle below the lighter liquids.

Source: Water Treatment Plant