Photo of a home water softener systemReverse Osmosis Treatment Systems
Using RO 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
  • POST a QUESTION or READ FAQs about choosing, installing, maintaining & repairing RO (reverse osmosis) water purifiers and water treatment systems
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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.

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Reverse Osmosis Systems for Water Purification

Reverse Osmosis POU System (C) Daniel Friedman

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.)

Watch out: if you are planning to purchase a revers-osmosis or "RO" water treatment system, confirm that it has been certified to comply with NSF / ANSI Standard 58 Reduction Claims for Reverse Osmosis Drinking Water Treatment Systems.

What contaminants do reverse osmosis water treatment systems remove?

Compact reverse osmosis RO system - InspectApedia

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.

Photo of a home water softener system

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.

See REVERSE OSMOSIS CONCENTRATE WASTE DISPOSAL for a discussion of the effects of disposing of reverse osmosis water treatment equipment wastewater - RO concentrate - into septic tanks and drainfields.

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.

This question was posted originally at WATER FILTERS, HOME USE

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

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:

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:

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


Continue reading at REVERSE OSMOSIS CONCENTRATE WASTE DISPOSAL or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.


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