Page 81 - Industrial Wastewater Treatment, Recycling and Reuse

58 Industrial Wastewater Treatment, Recycling, and Reuse

3. Treatment of excess sludge
4. Release/recycling of treated wastewater
5. Sludge disposal.
The preliminary treatment generally requires a combination of various
methods such as coagulation, sedimentation, and filtration. The choice of
biological method depends on various factors. The conventional activated
process was highly popular, especially before 2000. However, increased
awareness of the cost of operations has made use of the anaerobic process
more attractive in recent years. The organic load in food industry wastewa-
ters is usually very high, thereby making wastewater more suitable for anaer-
obic processes for generation of energy. The high volume of sludge
generated during conventional ASP is also driving industries to adopt
new changes such as the MBR and specific modifications for near zero-
sludge generation. A polishing treatment in the form of adsorption is typi-
cally used for meeting stringent standards for effluent discharge.

1.6 INDUSTRIAL WASTEWATER TREATMENT PROCESS
ENGINEERING

Industrial and sewage wastewater treatment essentially falls in the category of
dilute separations wherein ppm concentrations of pollutants are involved.
The wastewaters can be further divided into subclasses:
1. Wastewaters requiring removal of ionic species from aqueous streams. This
would include salts and inorganics such as metal ions in the wastewaters.
2. Wastewater streams requiring removal of organic pollutants from aque-
ous streams.
Identification of wastewaters containing components of high value for
removal and recovery is an important aspect that needs attention prior to
the treatment of the streams. The separation operations for removal and
recovery of high-value materials mainly involve adsorption, ion exchange,
and membrane separations (UF/NF/RO). Although these operations are
used currently in the industry, there are a number of limitations, and
applications in most cases can be said to be underdeveloped in terms of avail-
ability of suitable material, capacity, selectivity, chemical and thermal stabil-
ity, effective regeneration, and proper understanding of the phenomena.
In general, for the removal of suspended solids (TSS), sedimentation,
MF, filtration, and coagulation processes are most suitable and commonly
employed. Multimedia filtration, coagulation, and UF are also useful for