Page 118 - Industrial Wastewater Treatment, Recycling and Reuse

92 Industrial Wastewater Treatment, Recycling, and Reuse

PSAFC would improve performance over PAC under certain conditions. All
these variations have profound impact on the performance behavior in the
coagulation process and manufacturers usually specify which product suits
which wastewater treatment application. These improvisations directly
impact the process efficiency, and with improved performance, reduced dos-
age, and wider pH applicability along with better economics, these products
are finding increased acceptability over conventional coagulants.
Further advancement in the coagulation process can be achieved through
the use of additives that are responsible, by and large, for improving floccu-
lation and thereby easy, speedy separation with compact sludge volume.
These additives can be inorganic or organic. In fact, most organic polymers
perform the role of flocculant more than as coagulant.
Apart from the development of newer coagulants, a more common
approach in recent years is to integrate advantages of inorganic and organic
coagulants in the form of coagulant formulation (through physical blending
or chemical/functional modifications). This substantially improves cost
effectiveness apart from process performance. In general, inorganic coagu-
lants produce smaller and lighter flocs that require more time to settle.
Sludge volume is always greater with inorganic coagulants. Most inorganic
coagulants are pH sensitive and therefore work only in a narrow pH range.
Some of the disadvantages of common inorganic coagulants can be elimi-
nated with the use of organic coagulants or formulations of both inorganic
and organic coagulants. Any two or more coagulants can be combined to
enhance the effect of coagulation. It makes sense to combine inorganic
and organic coagulants to exploit the advantages of both types.
Although many new coagulants and formulations have been recently
developed for a variety of industrial wastewater treatment applications, there
is still a huge potential for further modifying the performance of existing
materials/methods and developing newer hybrid materials in the form of
coagulant formulations.

2.2.3.1 Electro-coagulation and Cavigulation
There are some new developments in the area of conventional chemical
coagulation processes. Electro-coagulation, although conceptually not
new, gained attention in recent years due to lower costs (mainly through
reduced power consumption), better efficiencies, and compact reactor
configurations. It belongs to a class of electrochemical processes wherein
the electrical source is used to generate coagulating species. The principle
is similar to chemical coagulation, except that in place of chemicals, here