What is TDS in water?

Water is often described as a universal solvent due to its ability to dissolve a vast array of substances. While pure water solely consists of H₂O molecules, the water we encounter in our daily lives contains various dissolved solids.

These dissolved solids, measured as Total Dissolved Solids (TDS), significantly impact the quality and taste of water. Understanding TDS is crucial for evaluating water suitability for consumption, household use, and industrial applications. 

What TDS is and what its sources are

TDS refers to the total concentration of dissolved inorganic and organic substances in water. These substances include minerals, salts, metals, cations, anions, and trace elements. It is typically measured in milligrams per litre (mg/L) or parts per million (ppm), indicating the mass of dissolved solids per unit volume of water.

TDS in water originates from both natural and human-induced sources. Natural sources include weathering of rocks and soil, dissolution of minerals, and decomposition of organic matter.

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Human activities such as agricultural runoff, industrial discharges, sewage, and urban stormwater also contribute to elevated TDS levels. Additionally, water treatment processes like disinfection and pH adjustment can introduce specific ions into water, further affecting TDS.

Common constituents of TDS

TDS comprises various inorganic salts, predominantly calcium, magnesium, potassium, sodium, bicarbonates, chlorides, and sulfates. These ions are essential for human health in moderate amounts but can cause issues at elevated levels. For instance, high calcium and magnesium content can lead to water hardness, resulting in scaling and reduced soap lathering. Sodium can impart a salty taste and pose concerns for individuals with hypertension.

Impact of TDS on water quality

TDS influences the taste, odour, and appearance of water. High TDS levels often impart a mineral or salty taste, affecting the palatability of drinking water.

Certain dissolved solids like iron and manganese can cause staining and discolouration of fixtures and laundry. Additionally, elevated TDS can impede the effectiveness of cleaning agents and industrial processes. Moreover certain constituents within TDS can have adverse health effects. For example, excessive nitrate levels from agricultural runoff can lead to methemoglobinemia, particularly in infants.

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High fluoride concentrations, especially in groundwater, can cause dental fluorosis and skeletal fluorosis. Therefore, monitoring and regulating specific TDS constituents is crucial for ensuring water safety.

Managing TDS in water

The World Health Organisation (WHO) recommends a maximum TDS level of 500 mg/L for drinking water. However, this is just a guideline, and the acceptable TDS range can vary depending on local regulations and individual preferences. In general, TDS levels below 300 mg/L are considered good for drinking water, while levels exceeding 1200 mg/L may be unpalatable and aesthetically undesirable.

Several methods are available to manage and reduce TDS in water. Reverse Osmosis (RO) is a highly effective filtration process that removes a significant percentage of dissolved solids, producing purified water with low TDS levels.

Distillation involves boiling water and condensing the vapor, leaving behind dissolved impurities and resulting in pure water with minimal TDS. Deionisation (DI) uses ion exchange resins to remove charged ions from water, thereby reducing TDS levels.

Electrodialysis Reversal (EDR) employs an electric field and semi-permeable membranes to separate ions from water, effectively reducing TDS. Choosing a suitable water purifier with the appropriate filtration technology (RO, activated carbon, etc) can help effectively reduce TDS levels in drinking water. The choice of treatment method depends on the desired water quality, specific TDS constituents, and available resources. It is advisable to consult water treatment professionals to determine the most suitable method for your specific needs.

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Total Dissolved Solids (TDS) plays a crucial role in assessing water quality. By understanding TDS and its constituents, we can make informed decisions about water treatment and consumption. While moderate TDS levels are often beneficial, excessive TDS can impact taste, aesthetics, and industrial processes. By employing appropriate treatment methods, we can effectively manage TDS and ensure access to safe and palatable water for various purposes.