13.9.2 Demerits of the Coagulation/Flocculation Process
1. Optimization of dose. For efficient C/F process, the dose of coagulant should be
optimized regularly. A lower dose of coagulant may cause insufficient destabilization, while an overdose of coagulant results into re-stabilization of colloidal
particles (Melia 1990; Elimelech and Melia 1990).
2. Regular monitoring on pH and metal solubility. The theoretical minimum solubility of different metals occurs at different pH. The solubility of metals must be
controlled in a mixture of metals. Also, pH may vary with the variation in dose
and characteristics of effluent. Thus, both of the parameters must be checked
regularly on fixed intervals.
3. Massive sludge generation. Many coagulants such as alum, ferric chloride, etc.
result in the generation of a tremendous amount of sludge that further requires
another treatment before disposal. Also, the dewatering of sludge and its digestion require additional space and cost.
4. Cost and availability of coagulants. The cost of the coagulant and its easy
availability are still a limiting factor on total treatment cost (Verma et al. 2011).
5. Residual impacts. If sulphide is present in the coagulant, scaling and corrosiveness will occur to the pipelines or tank accessories. Also, the concentration of
alum in the effluent or sludge will cause Alzheimer’s or other neurological
diseases to human beings (Banks et al. 2006, Polizzi et al. 2002). Similarly,
iron-based coagulant requires more skill as they are corrosive and deliquescent
(Li et al. 2008).
13.10 Compatibility of the Coagulation/Flocculation
Process with Other Treatment Options
To overcome the limitation of the coagulation/flocculation process for the treatment
of dye wastewater, a number of researchers have investigated the combination of two
different processes to reduce the demerits of the two processes and avail their
advantages. The dye released from textile industries is recalcitrant and resistant to
degradation; therefore, a single treatment process is not much reliable and economical to meet the regulatory discharge limits of the industries. Nowadays, combined or
hybrid system (Fig. 13.6) has been developed to efficiently curb the environmental
pollutants such as heavy metals or dyes (Su et al. 2016; Man et al. 2012; Lin and Lin
1993).
The combined treatment process includes sequential treatment method in which
one process ends and another process starts simultaneously. In this process, the
sequence of the treatment process is the same as written. Contrary to this, a hybrid
method is the process of fusion of two or more treatment process into a single
operation. Consequently, researchers have reported the performance and advantages
of the combined or hybrid treatment process for dye wastewater, as summarized in
Table 13.3.
13 Role of Coagulation/Flocculation Technology for the Treatment of Dye. . .
325
1. Optimization of dose. For efficient C/F process, the dose of coagulant should be
optimized regularly. A lower dose of coagulant may cause insufficient destabilization, while an overdose of coagulant results into re-stabilization of colloidal
particles (Melia 1990; Elimelech and Melia 1990).
2. Regular monitoring on pH and metal solubility. The theoretical minimum solubility of different metals occurs at different pH. The solubility of metals must be
controlled in a mixture of metals. Also, pH may vary with the variation in dose
and characteristics of effluent. Thus, both of the parameters must be checked
regularly on fixed intervals.
3. Massive sludge generation. Many coagulants such as alum, ferric chloride, etc.
result in the generation of a tremendous amount of sludge that further requires
another treatment before disposal. Also, the dewatering of sludge and its digestion require additional space and cost.
4. Cost and availability of coagulants. The cost of the coagulant and its easy
availability are still a limiting factor on total treatment cost (Verma et al. 2011).
5. Residual impacts. If sulphide is present in the coagulant, scaling and corrosiveness will occur to the pipelines or tank accessories. Also, the concentration of
alum in the effluent or sludge will cause Alzheimer’s or other neurological
diseases to human beings (Banks et al. 2006, Polizzi et al. 2002). Similarly,
iron-based coagulant requires more skill as they are corrosive and deliquescent
(Li et al. 2008).
13.10 Compatibility of the Coagulation/Flocculation
Process with Other Treatment Options
To overcome the limitation of the coagulation/flocculation process for the treatment
of dye wastewater, a number of researchers have investigated the combination of two
different processes to reduce the demerits of the two processes and avail their
advantages. The dye released from textile industries is recalcitrant and resistant to
degradation; therefore, a single treatment process is not much reliable and economical to meet the regulatory discharge limits of the industries. Nowadays, combined or
hybrid system (Fig. 13.6) has been developed to efficiently curb the environmental
pollutants such as heavy metals or dyes (Su et al. 2016; Man et al. 2012; Lin and Lin
1993).
The combined treatment process includes sequential treatment method in which
one process ends and another process starts simultaneously. In this process, the
sequence of the treatment process is the same as written. Contrary to this, a hybrid
method is the process of fusion of two or more treatment process into a single
operation. Consequently, researchers have reported the performance and advantages
of the combined or hybrid treatment process for dye wastewater, as summarized in
Table 13.3.
13 Role of Coagulation/Flocculation Technology for the Treatment of Dye. . .
325