RO - Advanced Water Treatment
Here
Today, Here Tomorrow
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Summary: This article
discusses several reasons for the current boom in advanced water
treatment. In the forefront of this necessity will be a great need
for water treatment professionals and their various skills. One
thing is for sure -- the trend will continue into the distant
future. |
Waterborne diseases are still responsible for a great number of human
deaths on the planet. A March 2003 press release from the Water Supply &
Sanitation Collaborative Council, established in 1990 under a mandate of
the United Nations, states that lack of "hygiene, sanitation, and a safe
water supply .. causes some three million deaths every year... and that
some 1.1 billion people are without access to safe water supply." Most
of the deaths are women and children in developing countries.
Developed countries, including the United States, have essentially
eliminated the biggest waterborne diseases such as cholera, typhoid and
dysentery. This has been the result of adequate sewage treatment and
treating drinking water by using conventional water treatment
technologies--clarification, filtration and disinfection with chlorine.
During the last century, our understanding of chemistry has grown
dramatically. We've been able to create hundreds of thousands of new
organic compounds such as solvents, detergents, pesticides, herbicides,
pharmaceutical drugs, plastics and many more.
Concurrent
with the creation of new compounds in the origin of waste products
disposed in wastewater. Many industrial and municipal waste products
travel in wastewater steams to the local sewage treatment plant. In they
aren't removed in the sewage treatment process, they typically enter a
surface water used downstream by others as a source water supply for the
production of drinking water. There are a variety of toxic substances in
source water that can cause human health problems. We now have an
additional concern - the deliberate contamination of drinking water to
cause disease and death. This is commonly called "bioterrorism".
Fortunately, the U.S. Environmental Protection Agency (USEPA), along
with drinking water professional everywhere, realize disease-causing
contaminants must be removed from our drinking water resources.
Increasingly, removal of pollutants requires advanced water treatment
technologies. Commonly used advanced water treatment technologies
include microfiltration (MF), ultrafiltration (UF), nanofiltration (NF),
reverse osmosis (RO), electrodialysis, electrodeionization (EDI),
ionexchange, ultraviolet irradiation and ozonation.
Many of U.S. military personnel around the world
primarily drink water that has been processed by advanced water
treatment technologies. The U.S. Army, Navy, Air Force, and Marines all
have high-tech water purification units. The Army has mobile RO Water
purification units that can operate in nuclear, chemical and biological
warfare conditions.
High-tech water treatment is able to remove
essentially all unhealthy substances from naturally occurring, disease
causing microorganisms to bioterrorism agents. Even contaminated
seawater can be purified into drinking water. Our continued creation of
contaminants drives an increasing need for advanced water treatment both
with drinking water and wastewater. The use of microfiltration and
ultrafiltration technologies is growing at a fast pace on the drinking
water treatment side and use of membrane bioreactors is growing on the
wastewater treatment side.
| Table 1.
Membrane materials demand |
| |
Millions of dollars |
Annual growth (%) |
| Item |
1998 |
2003 |
2008 |
03/98 |
08/03 |
| Membrane demand |
1,190 |
1,785 |
2,678 |
8.4 |
8.4 |
| Microfiltration |
626 |
860 |
1,175 |
6.6 |
6.4 |
| Ultrafiltration |
197 |
329 |
530 |
10.8 |
10.0 |
| Reverse Osmosis |
234 |
390 |
620 |
10.8 |
9.7 |
| Pervaporation |
24 |
52 |
81 |
16.7 |
9.3 |
| Other |
109 |
154 |
269 |
7.2 |
11.8 |
Membrane water treatment
As quality river, lake and well water resources are depleted,
less-desirable water sources must be purified for use as drinking water
and industrial water needs. In California and Florida, as well as in
many other coastal U.S. areas, the ocean has become the next water
resource.
The Tampa Bay Desalination Plant in Florida became
operational last year and produces 25 million gallons per day(17,400
gallons per minute), and was the first large seawater RO plant in the
United States. California is looking into several plants with a capacity
of up to over 100 million gallons per day.
People don't just want drinking water, however. People
want many things that are manufactured, and manufacturing processes
increasingly require high purity water. Almost all industries now
require high-tech water treatment. An example from a few industries
include:
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Food (juice concentration)
-
Dairy (cheese production)
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Beverage (beer, wine and soda production)
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Health & beauty (hypoallergenic skin products)
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Pharmaceutical (injected drugs)
-
Power generation (boiler feed water)
-
Semiconductor (microchip rinse water)
Power generation plants with high-pressure boilers require water that's
over a thousand times purer than drinking water. Without extremely pure
water going into high pressure boiler tubes scale and melt due to the
high temperature of the heat source (over 1,000°F)
and the lack of cooling once scaling occurs.
Semiconductor manufacturing plants require water over a
million times purer than drinking water. The circuitry on the most
advanced microchips today is so small that nearly 500 microchip "wires"
could be placed on the cut end of a human hair. If there are any
contaminants present in the ultrapure rinse water during manufacture,
the circuitry will electrically short. The purest water on Earth is
found in a microchip manufacturing plant.
MF and UF membrane products are increasingly being used in drinking
water treatment for the removal of Cryptosporidium oocysts and Giardia
lamblia cysts from surface waters. Within the industry, MF and UF
membranes are used to clarify or concentrate many different process
streams and waste streams.
NF membrane are increasingly used for the production of drinking water
from well water sources. The NF technology is used in an NF/RO
sequential treatment for making drinking water from seawater in Saudi
Arabia. There's a current pilot study in the United States to determine
the feasibility of NF/NF processing of seawater to drinking water.
RO membrane are
used wherever high purity water is required. RO units followed by EDI
units are common. Double-pass RO units followed by EDI units and
mixed-bed ion exchange units are also common. Semiconductor rinse water
production plants may have over 20 advanced water treatment steps
including several membrane water treatment steps to produce ultrapure
water.
Conclusion
Membrane water
treatment is booming. It will likely continue to boom due to the
expansion in the human population, the increased level of contaminants
in source waters because of waste products generated by the increasing
population, and the decreased availability of fresh water. The future is
bright for water treatment companies and individuals with the knowledge,
skills, and ability to meet the challenges and opportunities of the 21st
century.
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