Environmental Engineering Reference
In-Depth Information
Increasing # of organic
contaminants
Decreasing availability of clean
water sources
Decreasing $$ for infrastructure
Decreasing tolerance for industry
and government excursions
EPA monitoring endocrine-
disrupting compounds
Increasing awareness of health
and process effects
“I am convinced that... we will run
out of water long before we run
out of fuel.”
Nestlé chairman Peter Brabeck-
Letmathe
“EPA announces monitoring of 169
endocrine-disrupting compounds.”
Nov 2010
Nonmunicipal point-of-use
water treatment required
FIGURE 24.4
Regulations, water quality, and water demand all push toward the growing use of decentralized, point source
water puriication systems.
24.4 Strengths/Limitations of Current Water Treatment Technologies
Since each water treatment is constructed of multiple processes and technologies, it is
important to understand the strengths and limitations of these technologies. The pro-
cesses available for disinfecting and detoxifying water include
• Chlorination: The process of adding chlorine, a strong oxidant, to water is effec-
tive and widely used to disinfect water and to provide a residual disinfectant that
disinfects pipes and containers. However, in the presence of natural organic mat-
ter in the water, undesirable by-products can be formed, and some pathogens are
chlorine resistant. The taste and smell associated with this process have hindered
adoption in developing countries.
• Ozonation: Ozone, another strong oxidant, is also used in water treatment, to pro-
vide disinfection and some chemical breakdown. The process has narrow process
windows and can also produce undesirable by-products.
• Distillation: The process of boiling water and condensing the vapor removes a
broad range of contaminants; however, this is an energy-intensive process. Some
dissolved organics are transferred to the distillate, especially those with boiling
points near or below that of water. Thermal distillation for desalination can be
practical when using waste heat from power generation at large scales.
• Filtration: Including granular activated carbon, ceramic, or polymer microporous
ilters removes a moderately wide range of contaminants, but requires monitoring
and ilter replacement to assure continuous performance, and saturated ilter ele-
ments require regeneration or disposal.
• RO: This process applies pressure to a membrane to remove ionic and high molec-
ular weight contaminants from solution. RO effectively removes inorganic min-
eral salts, but typically requires signiicant energy and generates a waste stream
that has greater volume than the puriied water stream. It also fails to remove
many soluble organic contaminants, including some pharmaceuticals, petroleum
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