Generalities
23
De-oiling and degreasing
De-oiling removes floating oils from the surface of the wastewater (liquid-liquid separation)
using the dissolved air flotation method, while degreasing removes fats and grease suspended
or dissolved in the wastewater (solid-liquid separation) by adding certain chemical agents. The
aim of these two processes is to eliminate oils and greases that can hinder the effectiveness of
the biological treatment that follows (Metahri, 2012 in Mechref & Mahfouf, 2016).
1.2.2.1.2. Primary treatment (Physico-chemical treatments)
Primary treatment in the strict sense is a physico-chemical treatment that aims to eliminate a
large proportion of suspended mineral or organic matter by decantation or flotation (physicochemical sludge) (Moulin et al., 2013).
Settling performance can be improved by adding chemicals (ferric chloride, alumina sulfate...)
that will neutralize charged particles, thus increasing the probability of collision between
particles: coagulation and flocculation, (Figure 11), as well as the formation of flocs that are
subsequently easily settleable (Mecheref & Mahfouf, 2016).
Figure 11:Ilustration of Coagulation and floculation process to remove colloidal poluants
(Adewale 2014).
23
De-oiling and degreasing
De-oiling removes floating oils from the surface of the wastewater (liquid-liquid separation)
using the dissolved air flotation method, while degreasing removes fats and grease suspended
or dissolved in the wastewater (solid-liquid separation) by adding certain chemical agents. The
aim of these two processes is to eliminate oils and greases that can hinder the effectiveness of
the biological treatment that follows (Metahri, 2012 in Mechref & Mahfouf, 2016).
1.2.2.1.2. Primary treatment (Physico-chemical treatments)
Primary treatment in the strict sense is a physico-chemical treatment that aims to eliminate a
large proportion of suspended mineral or organic matter by decantation or flotation (physicochemical sludge) (Moulin et al., 2013).
Settling performance can be improved by adding chemicals (ferric chloride, alumina sulfate...)
that will neutralize charged particles, thus increasing the probability of collision between
particles: coagulation and flocculation, (Figure 11), as well as the formation of flocs that are
subsequently easily settleable (Mecheref & Mahfouf, 2016).
Figure 11:Ilustration of Coagulation and floculation process to remove colloidal poluants
(Adewale 2014).