1:5:10:365 EcoTip Blog

July 11, 2008

:193 Reverse Osmosis

Welcome to today’s 1:5:10:365 Tip for becoming a better steward for our home and planet environment.

1:5:10:193 EcoTip: Reverse osmosis is a method for reducing the amount of dissolved solids in drinking water. It works best in combination with other water purification methods since it will not remove volatile organic compounds.

RO involves forcing water through a semipermeable membrane with extremely fine pores.

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 Additional Information:

Suggested Review: :190, :191, :192

The following information is quoted from the third edition (released in May 2008 ) of Prescriptions for a Healthy House: A Practical Guide for Architects, Builders & Homeowners:

RO systems will remove a variety of ions and metals as well as some bacterial contaminants (cysts), but not coliform bacteria. RO systems will remove some arsenic (arsenic V but not the more toxic arsenic III). Reverse osmosis is well documented in the literature and in post-treatment testing proves to be effective in removing uranium, but NSF [National Sanitation Foundation] does not certify for uranium reduction, RO membranes eject the bulk of almost any dissolved and suspended contaminant including ionic, organic and silica compounds.

One criticism of reverse osmosis-filtered water is that it is stripped of essential minerals. Although this is true, it is a tradeoff for overall water quality. Most consumers do not depend on water for their nutritional needs but elect to take vitamin supplements or remineralize their RO water. Savvy water treatment companies use a crushed limestone (calcite) post-RO filter to impart a pleasant taste to the water. Parents sometimes express concern that RO removes fluoride added to municipal water for dental health purposes. This is true, but water fluoridation in general is a controversial issue and today most children under professional dental care receive whole-mouth fluoride treatments.

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July 10, 2008

:192 Carbon Water Filtration

Welcome to today’s 1:5:10:365 Tip for becoming a better steward for our home and planet environment.

1:5:10:192 EcoTip: Activated carbon in drinking water filters can help to remove chlorine and other volatile organic compounds. The length of time it takes the water to pass through the filter determines the amount of chemical that gets removed. The slower the water flow the greater the removal.

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 Additional Information:

Suggested Review: :190, :191

Be careful when interpreting the quality of a water purifier based on manufacturer’s claims. I was once asked to evaluate a purifier based on test results showing a 99% removal of chlorine. The problem was the manufacturer’s instructions said to install the filter so that it would deliver 1 gallon per minute, but the test was performed with the water being passed through the filter at a rate of 0.1 gallon per minute (ten times slower). The advertised test results were of course much better than what was being delivered to the client’s glass. To get the better results the client needed to slow the rate of filtration down to the test rate.

Chlorine removal performance is easy to test – you can visit any aquarium shop that sells tropical fish and purchase a sensitive chlorine test kit. 

If you want to compare chemical removal efficiency between purifiers before you purchase one, make sure the testing has been performed in compliance with National Sanitation Foundation standards. This will help make sure you are comparing units that have been tested in a consistent way.

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