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.
Operating Requirements, Pressure, Temperature for Reverse Osmosis Systems
Reade Question: what is the water tank height needed for a reverse osmosis system installation?
(June 6, 2015) HARI KRISHNA PODARALLA said:
What shall be the minimum height at which a water tank shall be placed, the tank from which a RO + UV water filter,draws water.
Reply: not height but feedwater operating pressures for RO systems are important
Hari I have not seen such a requirement; water is delivered to the filter by building water pressure; as long as the RO system you're installing is receiving adequate building water pressure it'll work.
A reverse osmosis system, to work, does need good water pressure.
Typical home reverse osmosis water filter systems are designed to function
between 30 psi and 100 psi of supply water pressure and
at temperatures between 40° and 90° F.
- "Referse Osmosis Membrane Operating Conditions and Performance Data", ESP Water Products
2460 McIver Lane, #200
Carrollton, TX 75006, Tel: 877-377-9876, Email,: firstname.lastname@example.org, retrieved 11/9/2015 original source https://www.espwaterproducts.com/reverse-osmosis-membrane-operating-conditions/
Best would be water pressure around 60 psi - a figure high enough to overcome the osmotic pressure and to cause the reverse-osmotic flow of water. This pressure (60 psi) is within the operating range of some but not all well pump systems. Note that I'm talking about RO system operating pressure (referred to by the RO people as "feedwater pressure") for a typical residential referse osmosis system. The actual pressure requirements for your system may also depend on the filter type your RO system uses (Cellulosic, aromatic polyamide, or thin film composite).
RO System Water Hardness Operating Range
The water hardness handled by RO systems is typically 0 to 350 mg/L or under 20 grains of hardness per gallon (gpg) - ESP Op.Cit.
RO System Water Supply Iron, Manganese, Hydrogen Sulfide, and Chlorine Content Operating Range
RO systems whose specifications we reviewed operate at the following chemical level ranges, that is, will work accepting water with these levels of chemicals:
Chlorine - zero (i.e. none needed)
Hydrogen Sulfide (H2S) "sulphur odors" - 0.1 to 10.0 mg/L
Manganese (Mn) - 0.00 mg/L (some systems may offer a different numbrer - Ed).
Iron (Fe) - 0 to 0.05 mg/L - ESP Op.Cit.
RO System Ph Operating Range
Depending on the system type and water source (community, private well and other codes that may apply) RO systems operate in the pH Range of 3.0 to 11.0. Note that the specifications for operation of any RO system depend also on the filter type that is in use. - ESP Op.Cit.
RO System Operating Pressures for Desalination of Water for Drinking
An RO system used for salt water de-salination operates at much higher pressures, ranging from 250-400 psi for grackish water to 800-1000 psi for the desalination of seawater. - "Desalination by referse osmosis", Organization of American States, OAS, retrieved 11/9/2015 original source: https://www.oas.org/dsd/publications/Unit/oea59e/ch20.htm
RO System Supply Water Turbidty Operating Range
RO systems whose specifications we reviewed operate at any turbidity level under 1.0 Net Turbidty (NTU) - an expression of the maximum level of total dissolved solids (TDS) in the water supply.
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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Handbook of Disinfectants and Antiseptics, Joseph M. Ascenzi (Editor), CRC, 1995, ISBN-10: 0824795245 ISBN-13: 978-0824795245 "The evaluation of chemical germicides predates the golden age of microbiology..." -
This well-focused, up-to-date reference details the current medical uses of antiseptics and disinfectants -- particularly in the control of hospital-acquired infections -- presenting methods for evaluating products to obtain regulatory approval and examining chemical, physical, and microbiological properties as well as the toxicology of the most widely used commercial chemicals.
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Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
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The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
Special Offer: For a 10% discount on any number of copies of the Home Referen
ce Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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