Does reverse osmosis remove arsenic and nitrate?

RO can reduce both when the system is designed and certified for them, with appropriate pre-treatment. For arsenic, the species present matters, so confirm the certification and retest after installation.

Is RO water safe to drink long-term?

RO drinking water is widely used. It removes minerals along with contaminants; some people remineralize for taste. For health-based contaminants, RO is a recognized point-of-use option — verify certification for your target.

Filtration & Treatment

Reverse Osmosis for Well Water: When It Makes Sense

Reverse osmosis pushes water through a membrane to remove many dissolved contaminants. It’s often a point-of-use solution for arsenic, nitrate, and more.

By Know Your Well Water Editorial TeamReviewed October 28, 20262 min read

Quick Answer

Reverse osmosis (RO) forces water through a semi-permeable membrane, removing a wide range of dissolved contaminants — often including arsenic, nitrate, and many salts. It’s commonly installed as a point-of-use system under the sink for drinking and cooking water. RO needs suitable pre-treatment, wastes some water, and should be certified (NSF/ANSI 58) for your target contaminant.

What RO is good for

Reducing arsenic, nitrate, and many dissolved ions at a single tap.
Improving taste where TDS is high.
A focused, lower-cost option when only drinking water needs treatment.

Limits and requirements

RO membranes can be damaged by iron, hardness, or sediment — pre-treatment and pre-filters matter.
RO produces reject (waste) water; efficiency varies by system.
For contaminants like arsenic, the species (III vs. V) affects removal — confirm the system is certified for your case.
Point-of-use RO treats one tap; it is not whole-house disinfection or softening.

Certify for the contaminant

Look for NSF/ANSI 58 certification and confirm the specific contaminant reduction claim (e.g., arsenic, nitrate) for the exact model — general “RO” marketing is not proof of a specific reduction.

Maintenance

Replace pre-filters and the membrane on the manufacturer’s schedule, and retest periodically to confirm the system is still performing. Our cost calculator can project filter and membrane replacement over several years.

Frequently asked questions

Does reverse osmosis remove arsenic and nitrate?: RO can reduce both when the system is designed and certified for them, with appropriate pre-treatment. For arsenic, the species present matters, so confirm the certification and retest after installation.
Is RO water safe to drink long-term?: RO drinking water is widely used. It removes minerals along with contaminants; some people remineralize for taste. For health-based contaminants, RO is a recognized point-of-use option — verify certification for your target.

Sources & references

NSF/ANSI Standards for Drinking Water Treatment Units — NSF, accessed October 28, 2026
Protect Your Home’s Water: Private Wells — US EPA, accessed October 28, 2026

This guide is documentary research and general information, not a laboratory analysis or professional assessment of your specific well. See our disclaimer.