Page 221 - Industrial Wastewater Treatment, Recycling and Reuse

Advanced Treatment Technology and Strategy 195

– Indian industries today face a severe shortage of skilled staffing, and
whatever is available has to be used for production and waste man-
agement. It requires lot of time to learn to operate biological systems,
especially when the characteristics are unpredictable.
A conventional system generates sludge/solid waste at different points, i.e.,
during primary treatment and from secondary treatment. Management and
disposal of the solid waste resulting from these stages is an issue because it
contains lot of active organic chemicals, bacteria, and other pollutants that
prevent its use as fertilizer and make it difficult to dispose of in landfills
because of the hazardous leachate generation.
Common effluent treatment plants (CETPs), which were established a
decade ago for treatment and management of wastewater from chemical
industries, have been ineffective in treating wastewaters using conventional
methods. The inability to treat wastewater has impacted industrial growth
and has adversely affected industrial expansion. There is an urgent need
to identify new commercially applicable technologies that can treat complex
industrial wastewaters.
Advanced oxidation technologies may resolve some of these issues. Key
aspects of advanced oxidation treatment are discussed in the following
section.

4.2 ADVANCED OXIDATION TREATMENT

The advanced oxidation process operates through different catalytic forms,
using oxidizing agents for degradation/mineralization of pollutants. The
Fenton process and the advanced electrochemical oxidation process are at
the foundation of advanced oxidation treatment processes. The principle
of the Fenton process is the catalytic cycle of the reaction between iron
(catalyst) and hydrogen peroxide (oxidant) to produce hydroxyl radicals.
The hydroxyl radical is produced according to the following reaction:
•

Fe 2+ +H 2 O 2 ! Fe 3+ +OH + OH
Although the Fenton reagent has been known for more than a century,
its application in an oxidizing process for destroying hazardous organics was
not realized until the late 1960s. The Fenton reagent is one of the most effec-
tive methods for oxidizing organic pollutants. The efficiency of the Fenton
2+
reaction depends mainly on H 2 O 2 concentration, the Fe /H 2 O 2 ratio, pH,
and reaction time. In addition, the initial concentration of the pollutant and