Page 142 - Industrial Wastewater Treatment, Recycling and Reuse

116 Industrial Wastewater Treatment, Recycling, and Reuse

separation in plating wastewater treatment indicated a feasible industrial appli-
cation for heavy metal removal in the future (Zuo et al., 2008).
The application of membrane technology involves two main compo-
nents, membrane element and membrane housing (membrane module).
The basic membrane element comprises a single membrane or hybrid mem-
brane system and is characterized in terms of membrane material, membrane
porosity, and physical and chemical characteristics of the membrane. The
membrane is the heart of the membrane separation system and dictates
the separation behavior. The membrane material can be organic or inor-
ganic. The membrane module is important from the point of view of mem-
brane application in wastewater treatment; it can come in different formats
such as a flat sheet module or spiral wound or hollow fiber. Usually, in
wastewater treatment, organic membranes such as cellulose acetate, poly-
propylene, polyamides, acrylonitrile, and polytetrafluoroethylene are most
commonly employed. The versatility and functionality of membranes make
precise application of membrane technology most challenging, in spite of
the theoretical possibility for achieving pollution control goals. In many
applications, membrane processes have to compete directly with one or
more conventional physico-chemical processes. As compared to conven-
tional processes, membrane processes are often believed to be more energy
efficient and simpler to operate, and to yield higher quality products with
low impact on the environment, because no hazardous chemicals are used
that have to be discharged. However, this may not be true in all cases, and
there are many limitations even today, especially in industrial wastewater
treatment areas that severely restrict the application of membranes. The
important drawbacks of this technology are:
– In wastewater treatment processes, the long-term reliability has not
completely been proven.
– It may require excessive pretreatment due to sensitivity to concentration
polarization, chemical interaction with water constituents, and fouling.
– Mechanical robustness is an issue due to the possibility of easy damage by
a malfunction in the operation.
– Process cost is a critical issue, although membrane separations, in general,
are considered quite energy efficient. The need to account for the con-
tribution of all direct and indirect costs such as energy consumption,
investment in membranes and modules, the cost of other process equip-
ment, the useful life under operating conditions, and various pre- and
post-treatment process costs in the calculation of overall cost is important
and can lead to higher costs.