Page 110 - Industrial Wastewater Treatment, Recycling and Reuse

84 Industrial Wastewater Treatment, Recycling, and Reuse

2.1.2 Devising a Solution for Industrial Wastewater Treatment
A systematic approach to wastewater treatment with a specific emphasis on
water recycling and reuse along with the recovery of valuable chemicals is
very important, especially for fine and specialty chemical and water-
intensive industries. This involves the basic characterization of the wastewa-
ter and understanding volumes and variations in the pollutant levels or
concentrations. A detailed approach in this regard has already been discussed
in Chapter 1.
A schematic flowchart of the main elements in the decision process for the
selection of an appropriate technology is presented in Figure 2.2. It is impor-
tanttodefinetheproblemandgoalsinlightoftheavailabledataontheprocess
and effluent. The next step is to list all the methods that are technically feasible
totreattheeffluent.Ifrecoveryisimportant,thespecificmethodsforrecovery
must be identified and prioritized. Once this selection is done, the next step is
toidentifysuitablemethods,materials,andprocesses,followedbydistributing
the pollutant removal load among primary, secondary, and tertiary methods
of treatment. It is essential that the interrelationships between these methods
beunderstoodinordertomaximizetheefficiencyoftheoveralleffluenttreat-
ment process. With this evaluation, the technologies for primary, secondary,
and tertiary (if required) treatment are identified; then a techno-economic
feasibility analysis needs to be carried out. At this stage, process integration
options should also be considered. Because these alter the entire treatment
strategy, the process of selecting appropriate methods/materials again has
to be restarted and needs iterations until the most effective and techno-
economically feasible solution is reached.
The physico-chemical methods of treatment that can be considered are
the following:
1. Coagulation
2. Adsorption
3. Ion exchange
4. Extraction
5. Membrane separations
6. Oxidation
7. Cavitation.
Usually a combination of one or more processes is required to attain the
goals of the effluent treatment process. Further, many of the physico-
chemical methods can be aptly integrated with biological methods of treat-
ment; this aspect also requires careful consideration.