Reverse Osmosis Treatment Systems
for Contaminated Drinking Water
REVERSE OSMOSIS WATER TREATMENT - CONTENTS: Water treatment by using an RO or "reverse osmosis" water treatment system to remove bacteria, sulphur, odors. Water treatment equipment choices, pros and cons of each water purification method. Water treatment methods for contamination, bacteria, lead, minerals, etc. Water treatment choices for odors, smells, sediment, cloudiness. Water treatment methods for hardness & mineral content. Choices of types of water treatment equipment
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Revere osmosis treatment systems, RO systems for water purification:
Here we explain how to install, use, & repair or maintain drinking water reverse osmosis systems or RO systems as an option for high mineral content, odors, or for correcting unsanitary or unsatisfactory drinking water.
Reverse osmosis can remove most water contaminants including parasitges (Cyrptosporidium & Giardia), heavy metals including cadmium,, copper, lead, mercury, and other common water contaminants sometimes found in the water supply itself such as arsenic, barium, high levels of nitrates or nitrites, perchlorate, and selenium.
Definition of Reverse Osmosis or RO for water treatment
Reverse osmosis as used in water treatment systems is a purification process through which water molecules pass through a porous membrane while leaving other molecules, presumably of contaminants, behind.
Water pressure on the input side or supply side of the RO system is maintained at a higher force than that for "natural osmosis" which otherwise would allow water to flow in either direction across the membrane. Output from the RO system is taken from the "water only" side of the membrane and directed to drinking water faucets or other points of use.
Water on the supply side of the RO membrane along with contaminants accumulating there are flushed from the supply side of the RO membrane into the building's drain system.
How does reverse osmosis water treatment actually work?
Reverse osmosis (RO) systems take advantage of the ability of water molecules to pass through a filter cellulose acetate semi-permeable membrane which
at the same time keeps out many other (non-dissolved non-chemical) contaminants.
"Semi permeable" means that the membrane is in effect an ultra fine filter whose openings pass water at a molecular level, leaving other larger molecules behind.
Water pressure (usually at 40 psi or more) forces water molecules through the membrane, leaving behind certain water contaminants including bacteria and sediment. Water on the output side of the filter has been treated or purified, depending on the capacity of the particular RO system.
Our photo ( left) shows a small point of use (POU) reverse osmosis water purifier installed below a kitchen sink. (Also notice that the corroded trap needs to be replaced.)
What contaminants do reverse osmosis water treatment systems remove?
Reverse Osmosis " filters" like the compact RO system show at left themselves do not remove aesthetic contaminants such as dissolved chemicals, odors or bad tastes in the water supply.
For this reason some reverse osmosis water treatment systems include additional stages of pre or post filtering to remove bacteria, chemicals, odors, tastes.
Reverse Osmosis Water Treatment System Clogging
Watch out for water high in bacterial contamination. Reverse osmosis systems are not usually recommended for water supplies that are high in bacterial contamination because bacteria build-up on the input side of the RO filter tend to block and clog the system.
Watch out: also for water supplies high in sediment, debris, chemicals, odors, or bad tastes.
To avoid clogging the RO system a pre-filter to remove sediment may be needed, and to avoid chemical, taste, or odor complaints, a post-processing charcoal filter system may also be needed.
Reverse osmosis (RO) water purifiers (see sketch at below left) will remove nearly all water contaminants and also remove minerals from water leaving it soft and purified.
Reverse Osmosis Purifiers as Water Softeners
Unlike a conventional salt-based water softener, RO systems do not discharge salt into
the drain system, though they do discharge four gallons of waste water for every gallon of purified water produced.
Because the design and capacity of various RO systems varies, only if a reverse osmosis system is registered and listed as a water purifier, can it be relied on to handle bacterial contamination in the water supply.
Disposal of Reverse Osmosis Water Purifier Concentrate
As it becomes high in contaminants, water on the input side of the RO filter is flushed to a disposal location.
OPINION: this method works well for some contaminants, as a point-of-use system. RO wastes quite a bit of water and does not address some chemical contaminants.
We don't know (yet) which uses more discharge water - a water salt-based
water softener or an RO system. That's because the quantity of water "wasted" by a reverse osmosis system depends on the quantity of water that is demanded from its output side.
Reverse Osmosis Water Treatment Effectiveness Research
Beall, Gary W. "The use of organo-clays in water treatment." Applied Clay Science 24, no. 1 (2003): 11-20.
Childress, Amy E., and Menachem Elimelech. "Effect of solution chemistry on the surface charge of polymeric reverse osmosis and nanofiltration membranes." Journal of Membrane Science 119, no. 2 (1996): 253-268.
Davison, A. M., H. Oli, G. S. Walker, and A. M. Lewins. "Water supply aluminium concentration, dialysis dementia, and effect of reverse-osmosis water treatment." The Lancet 320, no. 8302 (1982): 785-787.
Drewes, Jörg E., Martin Reinhard, and Peter Fox. "Comparing microfiltration-reverse osmosis and soil-aquifer treatment for indirect potable reuse of water." Water Research 37, no. 15 (2003): 3612-3621.
Duranceau, Steven J. "Membrane practices for water treatment." (2001).
Fritzmann, C., J. Löwenberg, T. Wintgens, and T. Melin. "State-of-the-art of reverse osmosis desalination." Desalination 216, no. 1 (2007): 1-76.
Greenlee, Lauren F., Desmond F. Lawler, Benny D. Freeman, Benoit Marrot, and Philippe Moulin. "Reverse osmosis desalination: water sources, technology, and today's challenges." Water research 43, no. 9 (2009): 2317-2348.
Kang, Guo-dong, and Yi-ming Cao. "Development of antifouling reverse osmosis membranes for water treatment: a review." Water research 46, no. 3 (2012): 584-600.
Li, Xiao-yan, and Hiu Ping Chu. "Membrane bioreactor for the drinking water treatment of polluted surface water supplies." Water Research 37, no. 19 (2003): 4781-4791.
Malaeb, Lilian, and George M. Ayoub. "Reverse osmosis technology for water treatment: state of the art review." Desalination 267, no. 1 (2011): 1-8.
Mondal, S., and S. Ranil Wickramasinghe. "Produced water treatment by nanofiltration and reverse osmosis membranes." Journal of Membrane Science 322, no. 1 (2008): 162-170.
Nicolaisen, Bjarne. "Developments in membrane technology for water treatment." Desalination 153, no. 1 (2003): 355-360.
Ning, Robert Y. "Arsenic removal by reverse osmosis." Desalination 143, no. 3 (2002): 237-241.
Petersen, Robert J. "Composite reverse osmosis and nanofiltration membranes." Journal of membrane science 83, no. 1 (1993): 81-150.
Radjenović, J., M. Petrović, F. Ventura, and D. Barceló. "Rejection of pharmaceuticals in nanofiltration and reverse osmosis membrane drinking water treatment." Water Research 42, no. 14 (2008): 3601-3610.
Rautenbach, R., and Th Linn. "High-pressure reverse osmosis and nanofiltration, a “zero discharge” process combination for the treatment of waste water with severe fouling/scaling potential." Desalination 105, no. 1 (1996): 63-70.
Reynolds, Kelly A., Kristina D. Mena, and Charles P. Gerba. "Risk of waterborne illness via drinking water in the United States." Reviews of environmental contamination and toxicology. Springer New York, 2008. 117-158.
Tran, Thuy, Brian Bolto, Stephen Gray, Manh Hoang, and Eddy Ostarcevic. "An autopsy study of a fouled reverse osmosis membrane element used in a brackish water treatment plant." Water research 41, no. 17 (2007): 3915-3923.
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