Water conductivity measures how well water can conduct an electrical current. This property is not inherently negative but indicates the concentration of dissolved substances, primarily charged particles known as ions.
Understanding Water Conductivity
Water’s ability to conduct electricity directly depends on the concentration of conductive ions present. These ions typically originate from dissolved inorganic solids like salts and minerals, such as chlorides, sulfates, carbonates, calcium, magnesium, sodium, and potassium. Pure water, with very few ions, is a poor conductor of electricity, often having a conductivity range of 0.05 to 3 microsiemens per centimeter (µS/cm).
Common sources of these dissolved solids include natural mineral deposits that water flows through, agricultural runoff containing fertilizers and pesticides, industrial discharge, and urban runoff from sources like de-icing salts. Conductivity is typically expressed in microsiemens per centimeter (µS/cm) or millisiemens per centimeter (mS/cm); for perspective, drinking water usually ranges from 200 to 800 µS/cm, while seawater is about 50,000 µS/cm (or 50 mS/cm) due to its high salt content. Temperature also affects conductivity; warmer water generally has higher conductivity because ions move more freely.
When High Conductivity Becomes a Problem
While conductivity itself does not pose a direct health risk, the substances causing high conductivity can be problematic. For human health, high conductivity in drinking water often suggests the presence of various contaminants. For instance, it can indicate elevated levels of minerals like sodium, which can be a concern for individuals on low-sodium diets, or heavy metals such as lead and copper that may leach from pipes and pose serious health risks. High mineral content can also alter water’s taste, making it salty or metallic, which affects its appeal. The World Health Organization suggests that if conductivity exceeds 1,000 µS/cm, further testing is recommended to identify potential harmful substances.
High conductivity can impact infrastructure and appliances. Water with high levels of hard minerals, particularly calcium and magnesium, can lead to scale buildup in pipes, water heaters, and household appliances. This scaling reduces the efficiency and lifespan of these systems. Certain dissolved ions associated with high conductivity can also contribute to corrosion of plumbing materials.
Aquatic ecosystems are also sensitive to changes in water conductivity. Sudden or extreme increases in conductivity, especially if caused by pollutants like industrial runoff or sewage discharge, can stress or harm aquatic life. Such changes can disrupt the osmotic balance in fish and other aquatic organisms, making it difficult for them to regulate water in their bodies. Different species have varying tolerances to conductivity levels, and significant deviations from a typical range can indicate an environment unsuitable for certain aquatic inhabitants.
Addressing Elevated Water Conductivity
Reducing high water conductivity primarily involves removing dissolved solids and ions from the water. Several water treatment methods effectively achieve this. Reverse osmosis (RO) is a widely used and effective method that forces water through a semi-permeable membrane, filtering out a high percentage of dissolved ions and impurities. RO systems can typically remove about 90-99% of conductivity.
Distillation, another method, involves boiling water and collecting the condensed steam, leaving most impurities behind. This process effectively removes various contaminants, including metals and dissolved salts. Deionization (DI) uses ion-exchange resins that chemically bind to and remove charged ions from water, producing very pure water. Water softeners specifically target calcium and magnesium ions, which are primary contributors to water hardness and, consequently, to conductivity. The choice of method depends on the specific contaminants present and the intended use of the treated water.