Generalities
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 The desired level of treatment efficiency required.
 The cost and energy requirements of harvesting the biomass produced and valorizing
it (Al-Jabri et al., 2021).
• The Necessity of Pretreatment of Wastewater
Pretreatment is an essential step before introducing microalgae, as the presence of
certain compounds at high concentrations in wastewater can inhibit microalgal growth
(Tyagi & Couillard, 1988), Similary the turbidity and pH of wastewater could inhibit
this growth (Das et al., 2018). Growing microalgal biomass in wastewater that has
undergone pretreatment could reduce residual nutrients and turbidity in treated
wastewater, and improve microalgal growing conditions (Chen et al., 2016).
Among the most widely used pretreatment methods in wastewater, treatment is
electrocoagulation (Bellebia et al., 2012), This method has proven its effectiveness by
removing various chemical additives, turbidity and pathogens from wastewater
(Symonds et al., 2015).
• Biomass harvesting
Harvesting microalgae biomass from wastewater presents a number of technical and
operational challenges:
 Fouling and clogging: microalgae harvesting systems can be prone to fouling and
clogging due to the presence of organic matter, mineral deposits or other particles in the
wastewater, which can reduce harvesting efficiency and lead to the need for frequent
cleaning operations.
 Variability in microalgae characteristics: such as size, shape and density. This
variability can make harvesting more complex.
 High-energy costs: many microalgae harvesting methods, such as centrifugation,
require the use of energy-intensive equipment.
1.2.2.1.4.2. Mechanism of Treating Wastewater
 Nutrient uptake
Microalgae could use sunlight, soluble inorganic carbon dioxide, nitrogen
and other nutrients to increase their cell numbers while treating wastewater (Manickam, 2015
in Triantafyllidis, 2018).