Heavy metals are a growing concern for homeowners across the country. These contaminants can cause serious health problems if they are ingested in high levels. So, does reverse osmosis remove heavy metals from drinking water?
Reverse osmosis is an effective method for removing heavy metals from drinking water. RO works very well at reducing the concentration of dissolved metals. The removal efficiency for reverse osmosis with heavy metals is between 90% to more than 99.9% depending on the specific metal.
In this blog post, we will provide a detailed review of how reverse osmosis works and how it removes heavy metals from water. We will also discuss the pros and cons of using a reverse osmosis system to treat your drinking water.
Table of Contents
What Are Heavy Metals
Heavy metals are naturally occurring elements with a high atomic weight and density. They can be found in both the Earth’s crust and in waters around the world. They are widely distributed in the environment due to their multiple industrial, domestic, agricultural, medical and technological applications.
Heavy metals can have negative effects on human health and the environment. They are particularly dangerous because they accumulate in the body over time and can potentially cause serious health problems even at low levels of exposure.
Arsenic, cadmium, chromium, lead and mercury are especially poisonous which is why they are classified as Priority Pollutants. The following heavy metals are considered serious health risks:
- Antimony
- Arsenic
- Cadmium
- Chromium
- Lead
- Mercury
- Nickel
- Selenium
- Thallium
This list of heavy metal contaminants is the focus of this article.
How do heavy metals get in my water?
There are a variety of ways that heavy metals can enter your drinking water supply. They can come from natural sources like minerals in the ground or from human activity, like mining or manufacturing.
The most common pathway for heavy metals to contaminate our drinking water are:
- mining operations
- industrial production and use
- domestic and agricultural use of metal-containing compounds
- metal corrosion
Drinking water standards for heavy metals
The US Environmental Protection Agency (EPA) is responsible for setting national drinking water standards. The EPA regulates 90 contaminants, including heavy metals, under the Safe Drinking Water Act (SDWA).
Here are the federal drinking water standards, also known as maximum contaminant levels (MCLs) for heavy metals.
| Heavy Metal | MCL |
| Antimony | 6 ug/L |
| Arsenic | 10 ug/L |
| Cadmium | 5 ug/L |
| Chromium | 100 ug/L |
| Lead | Lead Rule |
| Mercury | 2 ug/L |
| Nickel | Not regulated |
| Selenium | 50 ug/L |
| Thallium | 0.5 ug/L |
The Lead Rule is based on corrosion control to prevent the leaching of lead and copper from old pipes. It requires utilities to monitor tap samples for lead at customer locations, with an action level set as 15 ppb. At these levels, the utility must take additional actions to reduce the corrosivity of the water.
Health Concerns with Heavy Metals
Heavy metals are a serious problem because they bioaccumulate. This means that the concentration of heavy metals in our bodies tends to increase over time. Compounds accumulate when they are taken up and stored faster than they are excreted or metabolized.
The toxicity of heavy metals depends on several factors. These factors include:
- dose (i.e., amount)
- route of exposure
- chemical species
- the age, gender, and genetics of the individual
These contaminants are considered systemic toxicants. They are known to cause organ damage, even at low concentrations. Several of these heavy metals are also classified as human carcinogens by EPA and the International Agency for Research on Cancer.
The health risks associated with heavy metals are summarized in the following table.
| Heavy Metal | Health Effects |
| Antimony | Increase in blood cholesterol; decrease in blood sugar |
| Arsenic | Skin damage or problems with circulatory systems, and may have increased risk of getting cancer |
| Cadmium | Kidney damage |
| Chromium | Allergic dermatitis |
| Lead | Infants and children: Delays in physical or mental development; children could show slight deficits in attention span and learning abilities
Adults: Kidney problems; high blood pressure |
| Mercury | Kidney damage |
| Nickel | Exposure can harm the lungs, stomach, and kidneys. Exposure to nickel may lead to cancer. |
| Selenium | Hair or fingernail loss; numbness in fingers or toes; circulatory problems |
| Thallium | Hair loss; changes in blood; kidney, intestine, or liver problems |
What Is Reverse Osmosis?
Reverse osmosis (RO) is a treatment technology that use a natural process known as osmosis to remove contaminants from water.
Osmosis occurs when water moves from a less concentrated solution to a more concentrated one through a semi-permeable membrane. Reverse osmosis, as the name implies, reverses this process by applying pressure to the contaminated water. The pressure forces the water through the RO membrane.
A reverse osmosis filter has a pore size of around 0.0001 micron. Water, which is smaller than this, can pass through the RO membrane. Contaminants, which are larger than the holes in the RO membrane, are left behind. The result is clean, filtered water that has had many of the impurities removed.
Reverse osmosis can remove many different types of contaminants from water, including:
- dissolved minerals
- bacteria
- viruses
- pesticides
- herbicides
- heavy metals
Learn more about reverse osmosis in my other articles:
Complete Guide to Under-sink Reverse Osmosis Filters
The Definitive Guide to Whole House Reverse Osmosis Filter Systems
Reverse Osmosis and Heavy Metals
Reverse osmosis is a very effective treatment method for heavy metals. It is widely used and is very well understood. Modern RO systems are relatively inexpensive and extremely reliable.
For this reason, reverse osmosis is considered a “go to” treatment method for heavy metals.
How effective is RO at removing heavy metals
Reverse osmosis can remove 90% to as much as 99.9% of heavy metals from drinking water. Each contaminant has its own removal efficiency for RO treatment.
The following table shows the range of documented treatment efficiencies for reverse osmosis with heavy metal treatment.
| Heavy Metal | Removal Efficiency |
| Antimony | 92-99% |
| Arsenic | 94-96% |
| Cadmium | 96-98% |
| Chromium | 91-99% |
| Lead | 96-98% |
| Mercury | 96-98% |
| Nickel | 98-99% |
| Selenium | 96-98% |
| Thallium | 96-98% |
Other Technologies that Remove Heavy Metals
Besides reverse osmosis, there are other treatment methods that can be used to remove heavy metals. Some of these other technologies are:
Distillation
Distillation is a process that uses heat to evaporate water and then condense it back into a liquid. This process can remove many different types of contaminants, including heavy metals.
Ion exchange
Ion exchange is a technology that removes minerals from water by exchanging them with other ions. This process can be used to remove heavy metals from water.
Conclusion
So, does reverse osmosis remove heavy metals from drinking water? The answer is yes – but there are a few things you need to know about how reverse osmosis works before you make a decision about which water treatment system is right for you.
Reverse osmosis is an effective method for removing heavy metals from drinking water. RO works very well at reducing the concentration of dissolved metals. The removal efficiency for reverse osmosis with heavy metals is between 90% to more than 99.9% depending on the specific metal. In this blog post, we will provide a detailed review of how reverse osmosis works and how it removes heavy metals.
If you’re considering installing a reverse osmosis system in your home, be sure to read our blog post carefully so that you understand everything you need to know about how this technology works!