Water contamination remains a significant concern for households sourcing water from private wells or compromised municipal systems. Boiling water is a common purification practice highly effective against many waterborne pathogens. However, this method is often mistakenly applied as a universal solution for all contaminants, including chemical elements and heavy metals. Arsenic, a naturally occurring metalloid, is an odorless and tasteless toxin that poses substantial health risks even at low concentrations in drinking water.
The Effect of Boiling Water on Arsenic
The popular belief that boiling water eliminates all impurities is incorrect when dealing with arsenic. Boiling is an effective sanitation method because the high temperature destroys biological contaminants, such as bacteria and viruses. Arsenic, however, is a mineral contaminant, and its chemical structure is unaffected by the heat of boiling water.
Instead of removing the toxin, boiling water actually increases the concentration of arsenic in the remaining liquid. When water is heated, pure water molecules turn into steam and evaporate, leaving the dissolved solids behind. Since the arsenic does not vaporize, the total mass of the toxic element remains in a smaller volume of water, thereby increasing its potency per sip. Relying on boiling as a purification strategy when arsenic is present is a serious public health mistake.
Sources and Types of Arsenic in Drinking Water
Arsenic is a naturally occurring element widely distributed in the Earth’s crust. It enters water supplies primarily through the natural weathering and dissolution of rocks and minerals. This geological process leads to elevated concentrations, especially in groundwater sources like private wells.
The element exists in two major forms: organic and inorganic. Inorganic arsenic, which is typically found in contaminated water, is the more toxic form and is classified as a carcinogen. This inorganic form occurs as arsenite (As(III)) and arsenate (As(V)).
Organic arsenic is generally considered less harmful to humans. Since the inorganic forms dissolve into drinking water, removal technologies focus on mitigating the risk posed by As(III) and As(V). Human activities, including mining operations, the burning of fossil fuels, and past agricultural use of pesticides, also contribute to localized contamination.
Proven Methods for Arsenic Removal
Since heat treatment is counterproductive, proper arsenic mitigation requires specialized filtration technology that can chemically or physically separate the dissolved metalloid from the water. Before selecting any treatment system, professional water testing is necessary to determine the exact concentration and the ratio of As(III) to As(V), as this affects the efficiency of the chosen method.
Reverse Osmosis (RO)
One of the most effective point-of-use (POU) methods is Reverse Osmosis (RO). This system forces water through a semi-permeable membrane that is fine enough to block dissolved inorganic contaminants, including arsenic. RO can remove up to 99% of arsenic and is highly effective against the more easily removed arsenate (As(V)) form. A drawback of this process is that it produces a significant amount of wastewater, which is flushed away to carry the contaminants with it.
Adsorption Media Filters
Adsorption media filters represent another reliable option, often used in whole-house or POU systems. These filters use granular materials, most commonly Activated Alumina or Iron Oxide, that chemically bind the arsenic compounds to their surface. Both activated alumina and iron-based media work by attracting and holding the arsenic ions as the water passes through.
While both RO and adsorption media are effective against As(V), the more difficult-to-remove As(III) often requires a pre-treatment step, such as oxidation, to convert it into the As(V) form for better removal efficiency. Regardless of the system chosen, regular maintenance and timely replacement of the filter media or RO membrane are necessary to ensure effective toxin removal.