Using reverse osmosis (RO) to reduce arsenic in well water? Leave a comment

I have a well with 1.9 ug/L total arsenic (As). Yes this is below the EPA action level of 10 ug/L. However, most states do have warnings indicating that longer term consumption of As below that level can still lead to health effects. So, I am looking to remove as much As as possible. RO seems to be a preferred method. I see a lot of information on its efficacy when As levels are high, but not as much info on how effective it is when As levels are low. Can anyone tell me how RO systems perform where As levels are already low?

Additional info:

  • There is some iron in the water, but there is already a water softener pre-treatment tank to take most of that out. Lack of staining in the
    toilet tanks would seem to confirm that it is working.

  • I don’t know if it is As(III) or As(V). I am aware that will impact performance. For the sake of this question let’s assume it gets
    converted to As(V)

  • Nitrate and chloride all test near the detection limits.

  • I am thinking along the lines of an under sink model rather than a whole house system.

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