Arsenic is a naturally occurring element found in the Earth’s crust. It can dissolve into groundwater and enter private wells, often without any noticeable taste, odor, or color. This lack of sensory indicators makes arsenic a silent concern in drinking water.
Long-term exposure to inorganic arsenic, the more toxic form, is linked to various health issues. These include an increased risk of certain cancers (skin, bladder, lungs), as well as cardiovascular and neurological effects. Identifying and removing this contaminant is important for health protection.
Detecting Arsenic in Well Water
Confirming arsenic presence and concentration in well water is the first step in addressing contamination. Since arsenic is undetectable by senses, specialized testing is necessary. Professional laboratory testing offers the most accurate results.
While DIY kits exist, they often lack the precision needed to accurately measure arsenic levels. A certified laboratory provides a detailed report, including total arsenic concentration and the breakdown into inorganic forms: arsenite (Arsenic III) and arsenate (Arsenic V). Understanding these forms is important because their removal efficiency differs among treatment technologies. The U.S. Environmental Protection Agency (EPA) sets a maximum contaminant level (MCL) for arsenic in public water supplies at 10 micrograms per liter (µg/L), also known as 10 parts per billion (ppb).
Common Arsenic Removal Technologies
Addressing arsenic contamination in well water involves various treatment technologies. These are broadly categorized into Point-of-Entry (POE) systems, which treat all water entering the home, and Point-of-Use (POU) systems, which treat water at a specific tap.
Adsorption Systems
Adsorption systems use media with a high affinity for arsenic, binding it to the material’s surface. Activated alumina, a common adsorbent, effectively removes arsenic, particularly arsenate. Iron-based media also binds arsenic. These systems require periodic media replacement as they become saturated.
Ion Exchange Technology
Ion exchange works similarly to a water softener, exchanging arsenic ions for other ions as water passes through a resin bed. This method is effective for both arsenate and arsenite, though arsenate is generally removed more efficiently. The resin requires regeneration with a salt solution when its capacity is exhausted, similar to a water softener.
Reverse Osmosis (RO) Systems
RO systems push water through a semi-permeable membrane under pressure. This allows water molecules to pass while rejecting larger molecules and ions, including arsenic. RO systems are highly effective at removing a wide range of contaminants, including both forms of inorganic arsenic. These are often POU systems, treating water at a single tap for drinking and cooking.
Distillation
Distillation involves heating water to create steam, leaving contaminants like arsenic behind, then condensing the steam back into purified water. This process effectively removes arsenic and other dissolved solids, producing very pure water. Distillation systems are typically POU units.
Oxidation/Filtration Systems
Oxidation/filtration systems remove arsenite (Arsenic III) by first converting it to arsenate (Arsenic V) through an oxidation step. Common oxidants include chlorine or potassium permanganate. Once oxidized, the arsenate is then removed by filtration. This method is particularly useful when arsenite is the predominant form of arsenic in the water.
Choosing the Right Removal System
Arsenic Form and Concentration
The form and concentration of arsenic in your water are key considerations. Some technologies are more effective at removing arsenate than arsenite, or vice versa, unless pre-oxidation is applied. Total arsenic concentration also influences system capacity and maintenance frequency.
Water Chemistry
Overall water chemistry significantly impacts system performance. Parameters like pH, alkalinity, and the presence of other contaminants (e.g., iron, manganese, sulfates) can affect removal efficiency. For instance, high iron levels may require pre-treatment for some adsorption media.
Water Usage and Flow Rate
Your household’s desired flow rate and daily water usage determine whether a Point-of-Entry (POE) system (treating all water) or a Point-of-Use (POU) system (treating water at a single tap) is more suitable.
Cost and Maintenance
Cost considerations include initial installation and ongoing operational costs (energy, media replacement, maintenance). Understanding maintenance requirements, such as filter replacement or backwashing, is important for long-term effectiveness and choosing a system that fits your upkeep capacity.
Maintaining Your Arsenic Removal System
Consistent maintenance is crucial for the continued effectiveness and longevity of any arsenic removal system. Each system type has specific requirements.
For adsorption and ion exchange systems, regularly replace the filter media or resin as it becomes saturated with arsenic. Reverse osmosis systems require periodic replacement of pre-filters, post-filters, and the RO membrane for optimal performance. Distillation units need regular cleaning to remove mineral buildup. Oxidation and filtration systems require monitoring oxidant levels and routine backwashing or media replacement.
Regardless of the system type, periodically re-test the treated water to confirm arsenic levels remain below the desired threshold. This verifies the system’s effective operation and indicates when maintenance or adjustments are needed. Adhering to manufacturer recommendations and conducting regular water quality checks ensures your system consistently provides water with low arsenic levels.