Page 42 - Industrial Wastewater Treatment, Recycling and Reuse

Industrial Wastewater Treatment, Recycling, and Reuse: An Overview 25

Adsorption
Biological
Oxidation
Zone-I Membrane
Coagulation
Ion exchange
1000
Extraction
Cavitation
No. of Publications 100 Zone-II

10

1
1970 1980 1990 2000 2010
Year
Figure 1.10 Trends in separation processes for wastewater treatment.

Zone II: Corresponds to processes such as extraction and cavitation,
which are less commonly employed in the industrial wastewater treatment.
For extraction, typical applications remove pollutants such as phenol and
such acids/organics from the wastewaters. The important drawback of
the extraction processes lies in the fact that the selection of an extractant
is very crucial, and the major cost is in the recovery of extractant, apart from
the cost of extractant itself. Further, loss of an extractant in the wastewater
can pose further pollution problems. As far as the cavitation process is con-
cerned, it is evident that up to 2000, there were a very few publications con-
cerning wastewater treatment, and there has been a marked increase in
interest after 2000. However, in terms of industrial applications in wastewa-
ter treatment, there is still a very long way to go.
There has been huge interest in membrane separations in wastewater
treatment with a number of modifications in the form of membranes and
technology (Figure 1.11). MF applications outnumber several other pro-
cesses, mainly due to the fact that these are required for removal of sus-
pended solids and for removal of larger molecules. After MF, there has
been a lot of attention to RO, which is again crucial in water recycling
and reuse. In comparison, research in the area of other membranes, espe-
cially NF, is far from being well developed.
Similarly, in the area of biological separations in wastewater treatment,
there is marked interest in the area of anaerobic treatment as compared to