Looking for solutions

Question: I wanted to know which home water purification system is best and safest. Most water purifiers use activated carbon for deodorizing and cleaning impurities; treating bacteria is where they differ. Some use ultraviolet radiation to inactivate the bacteria, others use iodine to kill bacteria, while others use reverse osmosis to clear the salts, which are harmful to the body. What is the better system? Is there a comparison on your website? I could not find this information and write to you for help.

Bhavik Khera

Answer: Your inquiry is not easily answered. The issue becomes identifying which class of contaminants must be reduced, as different technologies are required for different contaminants. Activated carbon is fine for removing certain odors, chlorine and certain organic compounds.  For bacteria and other microorganisms, halogen chemicals (chlorine, iodine and bromine) are among the best, and while ultraviolet radiation is effective in killing bacteria and most viruses, it leaves no residual for long-term disinfection. Reverse osmosis, while quite effective in removing most microorganisms, is not the best for bacterial reduction. Still, this technology is most effective for reducing salts, as you mentioned.

In the name of research

Question: I work on a research team, which is designing a study assessing, in part, drinking water quality. We are behavioral, not environmental, scientists and I am writing to you with the hope that you will take a moment to answer a few basic questions we have about the assessment of drinking water quality.

  1. If we want to determine a subject’s level of exposure to various toxins, will data from the local watershed or from the various water systems within it be sufficient, or do toxins often contaminate a dwelling’s water supply on a more micro, house-by-house level? If so, which drinking water toxins commonly vary between plumbing systems?
  2. Are you aware of any publicly accessible databases or recent studies that provide detailed information about the levels of toxins within different watersheds and their component water systems?

Any advice that you can offer us will be greatly appreciated. Thank you very much for your attention.

Noah Susswein
Dept. of Psychiatry
Univ. of Medicine and Dentistry of N.J.

Answer: We will respond to your questions in order.
1. If you could be more specific regarding your meaning of the word “toxins,” we can perhaps be more specific.  If you mean health-related contaminants—addressed by the USEPA Safe Drinking Water Act, which are controlled by the municipal water provider—this applies to the water treatment plant as well as the distribution system, roughly up to where the water leaves the street and enters the house. Toxins that may be produced by microorganism activity in drinking water distribution systems have been poorly studied, and are generally not regulated.  
With the exception of lead (which may be in the household plumbing materials of construction), contaminants such as heavy metals and organics are likely to be in the raw water supply, and thus identified and removed at the treatment plant.
Of course, households on individual wells are a completely different matter; although these water sources are almost always groundwater and less likely to be contaminated from human activity.
2. We aren’t aware of any databases of the sort to which you refer; however, you might want to look to the U.S. Geological Survey (www.water.usgs.gov) for this information. Hope this helps.


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