13.8.2 pH Value
pH value plays a vital role in the coagulation/flocculation process as, at optimum pH
only, the coagulant gets hydrolysed and the coagulation takes place. pH also affects
the charge of NOM functional group and dissolved organic matter, the charge of
dissolved-phase coagulant species and the surface charge of colloids and floc
particles (Letterman 1999). In dye wastewater, the optimum pH is highly
recommended for decolourization of the dyes as pH may change the charge of
dissolved organics.
13.8.3 Coagulant Dose
The amount of coagulant addition is an essential factor, and the effectiveness of
colloidal destabilization is highly correlated. An optimum dose is required for
specific water chemistry. A lower dose of coagulant may cause insufficient destabilization of colloidal particles leading to cloudy sample with no flocs, while an
overdose of coagulant results into re-stabilization of colloidal particles as the
concentration of counter ions increases (Melia 1990; Elimelech and Melia 1990).
Thus, an optimum dose of the coagulant is required to produce good flocs, and this
can be determined by using the jar test apparatus.
13.8.4 Turbidity
The higher concentration of colloidal particles provides an ample chance for contact
and building of good flocs and vice versa will occur if the colloidal concentration is
low. For both cases, an optimum dose, pH and coagulant aid should be determined
(Peavy et al. 1985).
13.8.5 Zeta Potential
The zeta potential measures the net charge of colloidal particles and is used to assess
the stability of the suspension. The more negative the charge, the higher the zeta
potential. As zeta potential increases, the repulsive forces between colloidal particles
increase, and the colloidal suspension becomes more stable (Wang et al. 2005).
While as the zeta potential approaches zero, the charge on the surface becomes so
low that attractive forces overcome the repulsive force and destabilization take
places. The magnitude of the zeta potential is measured by electrophoretic measurement of particles mobility in an electric field.
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S. Sonal and B. K. Mishra
pH value plays a vital role in the coagulation/flocculation process as, at optimum pH
only, the coagulant gets hydrolysed and the coagulation takes place. pH also affects
the charge of NOM functional group and dissolved organic matter, the charge of
dissolved-phase coagulant species and the surface charge of colloids and floc
particles (Letterman 1999). In dye wastewater, the optimum pH is highly
recommended for decolourization of the dyes as pH may change the charge of
dissolved organics.
13.8.3 Coagulant Dose
The amount of coagulant addition is an essential factor, and the effectiveness of
colloidal destabilization is highly correlated. An optimum dose is required for
specific water chemistry. A lower dose of coagulant may cause insufficient destabilization of colloidal particles leading to cloudy sample with no flocs, while an
overdose of coagulant results into re-stabilization of colloidal particles as the
concentration of counter ions increases (Melia 1990; Elimelech and Melia 1990).
Thus, an optimum dose of the coagulant is required to produce good flocs, and this
can be determined by using the jar test apparatus.
13.8.4 Turbidity
The higher concentration of colloidal particles provides an ample chance for contact
and building of good flocs and vice versa will occur if the colloidal concentration is
low. For both cases, an optimum dose, pH and coagulant aid should be determined
(Peavy et al. 1985).
13.8.5 Zeta Potential
The zeta potential measures the net charge of colloidal particles and is used to assess
the stability of the suspension. The more negative the charge, the higher the zeta
potential. As zeta potential increases, the repulsive forces between colloidal particles
increase, and the colloidal suspension becomes more stable (Wang et al. 2005).
While as the zeta potential approaches zero, the charge on the surface becomes so
low that attractive forces overcome the repulsive force and destabilization take
places. The magnitude of the zeta potential is measured by electrophoretic measurement of particles mobility in an electric field.
322
S. Sonal and B. K. Mishra