Page 144 - Industrial Wastewater Treatment, Recycling and Reuse

118 Industrial Wastewater Treatment, Recycling, and Reuse

reliability. MBRs have been used to treat a wide range of municipal and
industrial wastewaters, and currently they are believed to be installed at
more than 1000 sites in Asia, Europe, and North America (Kumar and
Roy, 2008). Enough reliable equipment and technological support are
commercially available to meet existing and developing demand.

2.4.1.2 Membranes in Wastewater Treatment: Future Needs
The application of membrane separations in wastewater treatment today
requires development of low-cost membranes with high surface area to vol-
ume; and development of high-temperature membranes (ceramic, metal),
nanocomposites, chemically inert membrane material, material suitable
for hydrophilic compounds in dilute streams, and mixed organic/inorganic
membranes. Designing or selecting the most appropriate membrane material
for a particular application is a crucial step since the choice of material can
change the efficiency of a process by several orders of magnitude. Not many
theoretical tools are available yet in this regard, and computer-aided mem-
brane design is still an emerging field. It is recommended that a database
search along with mathematical modeling and simulation can help in the
selection process. Mechanical robustness of the membranes is important
since any physical damage to the membrane element can create serious prob-
lems in the operation, requiring replacement of the membrane. It is also
required that commercialization of processes using membranes be demon-
strated for different industrial effluents to address scale-up issues. Further, it is
felt that the integration of membrane separation with other physico-
chemical methods can provide a satisfactory solution in many wastewater
treatment applications.

2.4.2 Advanced Oxidation Processes

Advanced oxidation processes (AOPs) have been commercially used in
wastewater treatment, especially for the removal of refractory pollutants.
They are preferably considered in the category of tertiary treatment pro-
cesses. When used as a secondary treatment step, the role of an AOP is to
degrade toxic pollutants and convert them into forms that can be treated
by other methods, such as biological treatment. The goals here differ
completely from conventional goals where complete degradation of organic
compounds is sought rather than partial degradation of compounds amena-
ble for treatment. AOPs are less preferred as technology if other methods are
applicable due to technology and cost reasons.