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The ways to reduce Total Dissolved Solids (TDS) in water are reverse osmosis (most common process, 90-99% removal of dissolved solids using a semi-permeable membrane), distillation (older technology, very pure water produced by evaporating and recondensing water), deionization (ion exchange technology, very pure water for specialty applications), ion exchange (removes offending ions and replaces them with more harmless counterparts, commonly used for water softening), and electrodialysis (eliminates ions from water through the use of an electrical current).
Every day, we use water, but the amount of water we use can be compromised by excess TDS. TDS stands for total dissolved solids, which refers to the cumulative concentration of all organic and inorganic material dissolved in water.
This guide will explore what TDS is, why high TDS levels can be an issue, and the different ways to reduce TDS in water.
Total dissolved solids include minerals such as calcium, potassium, and magnesium, salts, metals like lead, zinc, and copper, dissolved organic matter, and other inorganic substances.
TDS is measured in milligrams per liter (mg/L) or parts per million (ppm). The Environmental Protection Agency (EPA) recommends that all drinking water should not exceed 500 ppm of TDS to maintain its quality and taste.
TDS has anthropogenic and natural sources. Natural sources include water naturally dissolving small amounts of minerals as it flows through rock and soil formations, since water is mildly acidic in nature. Geological formations with a high composition of limestone, gypsum, or salt deposits can significantly contribute to the higher TDS.
Human-made sources encompass agricultural runoff, urban runoff, industrial wastewater, sewage effluent, and water treatment chemicals that can contribute additional dissolved solids to water bodies.
Excessive TDS levels in water can cause numerous health, equipment, and product quality issues. From a taste and aesthetic perspective, high TDS can create unpleasant taste profiles like bitter, salty, or metallic tastes, along with a discolored or cloudy water appearance that reduces the palatability of drinking water.
Equipment damage is another significant concern, as high TDS causes deposits in pipes, water heaters, and boilers, reduces the efficiency of heating elements, and shortens appliance life for appliances like coffee makers, ice machines, and dishwashers while increasing maintenance and energy consumption.
Food and beverage quality issues include cloudy ice cubes with a lower freezing point, poor-tasting coffee and tea, cloudy appearance in brewed beverages, reduced carbonation in fountain beverages, and unstable extraction in coffee and espresso brewing.
Agricultural impacts manifest as soil salinity when high-TDS water is used for irrigation, reduced crop yields and soil fertility, and salt accumulation in plant root zones.
Industrial problems encompass interference with many industrial processes that require high-purity water, corrosion of manufacturing plant equipment, and increased cost of production due to water treatment requirements.
Although TDS is usually a secondary contaminant (affecting taste rather than being directly hazardous), extremely high levels can contain some hazardous constituents, such as heavy metals or toxic compounds, that can pose health risks with long-term consumption.
There are several effective methods for reducing TDS levels in water. The best method depends on your specific water conditions, treatment goals, and budget.
Reverse osmosis is a highly effective and popular method for measuring water quality and reducing TDS in water. Water is forced against a semi-permeable membrane under pressure, which allows water molecules to flow through but rejects the majority of dissolved solids, salts, and impurities.
The advantages of reverse osmosis include being highly effective at rejecting 90-99% of dissolved solids, removing a wide range of contaminants like salts, minerals, heavy metals, and some organic compounds, being comparatively easy to install and maintain for home use, and having the ability to be scaled from under-sink home units to industrial applications.
The disadvantages include higher upfront costs than simple filtration, producing wastewater as a byproduct of the filtration process, removing beneficial minerals along with impurities, and requiring proper water pressure to function efficiently.
Distillation is one of the most ancient water purification methods that is extremely efficient at reducing TDS in water. Water is boiled, and the steam, now freed from most impurities and dissolved solids, is condensed back into liquid water.
The advantages of distillation include being very effective at removing most TDS and other impurities, producing very pure water with near-zero TDS, and requiring no replacement filters.
The limitations include being energy-intensive and relatively slow, having higher operating costs due to energy consumption, removing beneficial minerals, and allowing some volatile organic compounds to carry over with steam.
Deionization is well adapted to ultra-pure water applications. Water is filtered through ion exchange resins, which strip away positively charged (cations) and negatively charged (anions) dissolved solids and replace them with hydrogen and hydroxide ions that form water.
The advantages of deionization include producing extremely high-purity water with very extensive TDS removal, being extremely well suited to laboratory, pharmaceutical, and electronics manufacturing applications, and being more effective than distillation in water production rate.
The limitations include being more costly than other technologies, requiring frequent resin bed replacement or regeneration, not being customarily used in potable water due to total mineral removal, and being ineffective in removing organic substances and some non-ionic chemicals.
Ion exchange equipment is employed in softening water but may also reduce some TDS constituents. Water runs through resin beds to be replaced with purer ions containing fewer impurities. In water softeners, magnesium and calcium ions are replaced with sodium ions.
The advantages of ion exchange include effective removal of scale-forming minerals like magnesium and calcium, low cost compared to distillation or RO, simple operation and maintenance, and extending appliance and plumbing system life.
The limitations include not reducing total TDS significantly since it exchanges ions rather than removing them, requiring frequent regeneration with salt, introducing sodium into treated water, and being ineffective for removing most dissolved solids.
Electrodialysis uses an electric current to remove ionized impurities from water. An electric field forces ions across selectively permeable membranes, separating the ions from water.
The advantages of electrodialysis include being ideal for brackish water desalination, using lower energy than thermal processes, and achieving higher water recovery rates than RO.
The restrictions include having a multistep operation and complex system design, requiring additional initial capital, not being an ordinary system for household use, and being less effective with non-ionic compounds.
High TDS water purification is typically a multistep process that involves more than a single treatment process. The process begins with pre-treatment, which safeguards downstream equipment and overall efficiency prior to primary TDS reduction processes. This includes sediment filtration to remove suspended solids and particulates, carbon filtration to reduce taste, odor, organic chemicals, and chlorine, and water softening to remove hardness minerals like calcium and magnesium.
After pre-treatment, you should use one of the primary TDS reduction processes described above, such as reverse osmosis, distillation, deionization, ion exchange, or electrodialysis.
Based on water usage, post-treatment might be necessary, including remineralization to replace valuable minerals in water treated by RO or distillation, pH adjustment to neutralize acidified water, and disinfection to ensure microbiological safety with UV treatment or slight chlorination.
Regular maintenance is essential to maintain uniform functioning of your TDS reduction system, including regular monitoring of pre- and post-treatment TDS, timely replacement of filters, membranes, and other consumables, periodic sanitizing of the system to discourage biological growth, and professional maintenance in accordance with manufacturer recommendations.
While excessive TDS is unpleasant, it’s interesting to note that some amount of TDS is desirable for drinking water taste and mineral nutrition. Rather than eliminating TDS completely, target TDS optimization for taste and health. Here’s how to achieve this balance.
Selective TDS management involves targeting harmful constituents selectively, such as heavy metals, nitrates, and excess sodium, while preserving beneficial minerals like calcium, magnesium, and potassium, and balancing TDS concentrations since 50-150 ppm is generally optimal for drinking water taste.
Blending is a low-cost method of TDS concentration control that involves mixing high-purity treated water like RO water with filtered tap water to create a blended mixture with optimal mineral content, or using bypass valves on RO systems to allow partial untreated water blending with purified water.
For water treated by methods that strip nearly all minerals, like RO or distillation, remineralization options include installing calcium and magnesium remineralization filters, applying commercial mineral additives to drinking water exclusively, or investigating mineralizing and alkalizing water filtration systems.
Mindful water use helps conserve water supplies and minimize TDS accumulation by limiting water softener use and regeneration rates, employing environmentally friendly cleaning products and detergents, properly disposing of chemicals rather than flushing them down the drain, and actively supporting watershed conservation in your region.
Testing must be precise for effective monitoring and control of the TDS level.
The easiest and most convenient test for TDS – Digital conductivity meters measure the electrical conductivity of water, which is directly proportional to the concentration of dissolved ions, and then express this reading as an approximate measurement of TDS in ppm.
How To Use A TDS Meter?
The advantages of TDS meters include being inexpensive, providing immediate results, being portable, and being easy to use. The limitations include providing an estimate rather than the actual formulation and requiring occasional calibration.
For more detailed and accurate TDS measurement, laboratory analysis offers several options. The gravimetric method is an extremely precise laboratory method in which a water sample is filtered, evaporated, and weighed solids are measured. Ion chromatography measures the presence and amount of specific ions in the water, while inductively coupled plasma (ICP) analysis identifies trace metals and trace elements.
For easy testing, test kits and strips provide convenient options. Water quality test kits are multi-parameter kits that test TDS along with other water quality parameters, while TDS test strips are color-changing strips that provide an approximate TDS reading.
For the most comprehensive overall analysis, professional water testing options include state-certified water testing laboratories, water treatment companies that provide in-depth water analysis methods, and public water systems that provide water quality reports.
For critical applications or extended control, continuous monitoring systems offer inline TDS monitors that provide real-time readings, data logging systems that provide a record of TDS, and alarm systems that warn you when TDS exceeds levels you specify.
Total Dissolved Solids (TDS) is the overall amount of dissolved solids in water, reported in parts per million (ppm) or milligrams per liter (mg/L). While naturally occurring TDS contributes valuable minerals to drinking water, too much can cause a host of issues, including off-taste, equipment failure, and even potential health threats from certain contaminants.
Rather than stripping out all dissolved solids, aim for optimum TDS levels that retain beneficial minerals and reject undesirable impurities. Regular checks with TDS meters or professional water testing help monitor performance and ensure your water treatment equipment remains effective.
By understanding TDS and taking appropriate reduction steps, you can enjoy cleaner, fresher-tasting water and protect your plumbing, appliances, and perhaps your health from the effects of excessive dissolved solids. If you would like to learn more about TDS monitoring or what other water testing kits we offer, do not hesitate to contact the world-class team at Atlas Scientific.
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