Abstract

Wastewater treatment has been a challenge throughout the
world in line to the variable influent characteristics and strict regulations
of effluents. In response to this problem, a reliable and cost effective process
has been developed. A coupled of coagulation -flocculation method has been
applied for the treatment from different type of wastewater bearing with a high
concentrations of organic and hazardous pollutants. Wastewater will be treated
using coagulation-flocculation to remove high concentration organic pollutant
and heavy metals in wastewater. Inorganic coagulants are commonly used in the
process due to its low cost and ease of use. However, the application constrained
with low flocculating efficiency therefore organic polymeric flocculants is
added to increase the flocculate efficiency with low dosage of coagulant use. The effect of coagulant dosages and pH on the
coagulation-flocculation efficiency process was studied and conditions were
enhanced corresponding to the best removal of turbidity, total suspended solid
(TSS), total dissolved solid (TDS), biological oxygen demand (BOD), and chemical
oxygen demand (COD). However, the effect of combined coagulation-flocculation
treatment with carbon nanomaterials is more efficient than the conventional
coagulation-flocculation process. Advanced science and technology introduced
the combined adsorption in the process by using carbon based nanomaterials.
Carbon based nanomaterials is highly effective with great capacity to absorb a
wide range of contaminants, fast kinetic, and large specific surface area. It
also has lower production cost and accessibility compared to other
nanomaterials. This paper gives an overview on coagulation-flocculation and
combined coagulation-adsorption with carbon nanomaterialsfor the treatment of
wastewater.

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Keywords: Wastewater,
Coagulation, Flocculation, TSS, TDS, Turbidity, BOD, and COD, Removal, Carbon
Nanomaterials, Adsorption

 

1.0       Introduction

The water supply is
the fundamental requirements for human life. Without water, life cannot be
sustained beyond a few days and the lack of access to adequate water supplies
leads to the spread of disease (Guy Howard et al, 2003).The wastewater
treatment is involved in order to protect the quality of life and limited freshwater
resources. Discharging wastewater without treatment into surface water resource
can affect aquatic life negatively (Fuat et al, 2011).Wastewater highly
composed of suspended particles, dissolved organic and inorganic matter as well
as several biological organisms such as algae, bacteria and viruses. This
material has to be removed since water quality will be deteriorated. The very
important step in water and in wastewater treatment is the coagulation – flocculation
which is considered as one of the most important and widely used treatment
processes due to its simplicity and effectiveness. (N.D Tzoupanos, 2008).

Coagulation-flocculation
is a chemical water treatment methods applied in various wastewaters prior to
the sedimentation and filtration techniques to enhance the ability of a
treatment process in order to remove suspended particles from the wastewater.Most
suspended solids in wastewater takes a negative charge and they consequently
repel each other. This repulsion prevents the particle from agglomerating
causing them to remain in suspension. The process of coagulation-flocculation
takes place in different steps intended to overcome the forces stabilizing the
suspended particles and letting the particle collision and development of
flocs, which can be settled and filtered out of the water. This process
technique is comparatively simple and cost effective as long as those chemicals
are highly available and the dosage is adapted to the water composition.

In spite of the great
number of wastewater treatment heavy metal has become the most environmental
problem now a days. Therefore employing adsorption process by using nanomaterialsin
wastewater treatment has become the promising techniquein the recent yearsdue
to the adsorption properties and efficiency.  Carbon nanotubes (CNT’s) have been proven
effectively for removing heavy metals ions such as lead, chromium, copper and
nickel from wastewater(Haijiao et al. 2016).

 

1.1.       
Wastewater
Characterization

 

Wastewater is the
mixture of liquid and transported water wastes from communities in homes,
commercial buildings, and industrial facilities, along with any groundwater
infiltration and surface and storm water inflow that may enter the sewer system.
Understanding the characteristics of wastewater is very important since this
understand the reaction and interactions with the inorganic and organic
characteristics of compounds. The wastewater is also called sewage is mostly
water by mass (99%) and solids (0.1%) shown in Fig 1.0. (Michael et al.)The
contaminants in wastewater include the biodegradable organic compounds, suspended
solids, inorganic compounds, nutrients, metals and pathogenic microorganism.

Fig 1.0 Composition of Domestic
Wastewater

 

2.0 Coagulation-Flocculation
Method

 

Treatment
for surface water sources involves chemical and physical removal of particulate
matter by coagulation, flocculation, sedimentation, and filtration processes,
along with disinfection to inactivate any remaining pathogenic microorganisms. Coagulation-flocculation
is known as conventional method for wastewater treatment where the cationic
inorganic salts are used as coagulants and anionic polymers are used as
flocculants as shown in Figure 2.0 (TorOve L, 2009). Coagulation destabilizes
the particle’s charges with the help of the coagulants. The coagulants with
charges opposite to those of the suspended solids are added to the water to
neutralize negative charges and form a jellylike mass to bridge particles as a
result forming a large mass enough to settle or trapped in the filter (Johnson
PD, et al. 2008). On the other hand, flocculation is a process of whereby
stabilized particles, or particles formed as a consequence of destabilization,
are induced to come together, make contact, and thereby form large(r)
agglomerates (Bratby, 2006). The factors that influence the efficiency of
treatments are type and dosage of coagulant-flocculant, temperature, pH, mixing
time, speed and retention time.

 

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