chemical processes applied for the removal of contaminants suffer from several
limitations due to higher cost, energy requirements, basic properties alteration, and
its residual byproducts (Crini and Lichtfouse 2019). For resolving such challenges,
several types of green and sustainable approaches are developed by perceiving them
as an ecofriendly approach. These techniques require less energy cost-effective,
reliable, efficient, and highly accepted by the public. The different kinds of
approaches used for removing the contaminants from wastewater are discussed as
below:
6.5.1 Physicochemical Approach
Researchers are using different types of the physicochemical methods such as
gravity sedimentation process, coagulation, ion exchange, chemical precipitation,
adsorption through abiotic materials, catalytic removal and nanotechnology, etc., to
remove the toxic pollutants from the wastewater since many years.
6.5.1.1 Gravity Sedimentation Process
Sedimentation is a physical wastewater treatment process as well as also a part of
primary wastewater treatment process, in which gravity plays an important role in
the removal of suspended solids from the wastewater. Settlement ponds are used for
the removal of higher weight suspended particles from wastewater with the help of
sedimentation process. Clarifiers are built with mechanical means for consistent
removal of suspended solids from the wastewater. In sedimentation process, removal
of suspended solids is affected by its size and specific gravity (Demirbas et al. 2017).
6.5.1.2 Coagulation
In wastewater treatment, suspended materials of wastewater can be removed simply
through settling process, but for the removal of smaller particles especially for
colloidal particles, coagulation process plays an important role. Coagulation is a
chemical process and it is achieved through the use of different coagulants, e.g.,
aluminum chloride (AlCl 3 .6H 2 O), sodium aluminates (NaAlO 2 ), alum, ferrous sulfate, etc. Due to the use of coagulants, aggregation of destabilize particles, and
sedimentation substances form a larger particle called “Floc” and the process is
called flocculation. The advantage of these flocs due to higher weight can easily be
removed by sedimentation and filtration (Ebeling et al. 2003). Farhan (2019) analyzed the efficiency of different coagulants such as alum, ferrous sulfate and ferric
chloride, etc., with the addition of different organic coagulants, e.g., polyethylene
glycol, polyacrylamide, and inorganic, e.g., bentonite for removing higher and lower
turbidity of the wastewater. Optimal dose of coagulants is also determined for higher
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limitations due to higher cost, energy requirements, basic properties alteration, and
its residual byproducts (Crini and Lichtfouse 2019). For resolving such challenges,
several types of green and sustainable approaches are developed by perceiving them
as an ecofriendly approach. These techniques require less energy cost-effective,
reliable, efficient, and highly accepted by the public. The different kinds of
approaches used for removing the contaminants from wastewater are discussed as
below:
6.5.1 Physicochemical Approach
Researchers are using different types of the physicochemical methods such as
gravity sedimentation process, coagulation, ion exchange, chemical precipitation,
adsorption through abiotic materials, catalytic removal and nanotechnology, etc., to
remove the toxic pollutants from the wastewater since many years.
6.5.1.1 Gravity Sedimentation Process
Sedimentation is a physical wastewater treatment process as well as also a part of
primary wastewater treatment process, in which gravity plays an important role in
the removal of suspended solids from the wastewater. Settlement ponds are used for
the removal of higher weight suspended particles from wastewater with the help of
sedimentation process. Clarifiers are built with mechanical means for consistent
removal of suspended solids from the wastewater. In sedimentation process, removal
of suspended solids is affected by its size and specific gravity (Demirbas et al. 2017).
6.5.1.2 Coagulation
In wastewater treatment, suspended materials of wastewater can be removed simply
through settling process, but for the removal of smaller particles especially for
colloidal particles, coagulation process plays an important role. Coagulation is a
chemical process and it is achieved through the use of different coagulants, e.g.,
aluminum chloride (AlCl 3 .6H 2 O), sodium aluminates (NaAlO 2 ), alum, ferrous sulfate, etc. Due to the use of coagulants, aggregation of destabilize particles, and
sedimentation substances form a larger particle called “Floc” and the process is
called flocculation. The advantage of these flocs due to higher weight can easily be
removed by sedimentation and filtration (Ebeling et al. 2003). Farhan (2019) analyzed the efficiency of different coagulants such as alum, ferrous sulfate and ferric
chloride, etc., with the addition of different organic coagulants, e.g., polyethylene
glycol, polyacrylamide, and inorganic, e.g., bentonite for removing higher and lower
turbidity of the wastewater. Optimal dose of coagulants is also determined for higher
132
P. K. Singh and R. K. Sharma