Water is considered a universal solvent due to its ability to dissolve and absorb molecules of various substances. The number of particles dissolved in a volume of water is called total dissolved solids (TDS). Total dissolved solids can be either organic or inorganic. Knowing your water’s TDS and total dissolved solids gives you a complete picture of your water quality. Below, learn about the different types of total dissolved solids, how to measure them, and how to reduce total dissolved solids in water

What is TDS in Water?

Total Dissolved Solids (TDS) is the amount of inorganic and organic substances such as minerals, metals, salts and ions dissolved in a given volume of water. Simply put, total dissolved solids is a measure of everything dissolved in water except molecules of water (H2O).

When water comes in contact with a soluble substance, particles of the substance are absorbed into the water, producing total dissolved solids, since water is a solvent. TDS in water can come from almost anywhere, including the chemicals used to treat municipal water supplies, natural water sources, domestic plumbing systems, and even street and courtyard drains.

Type of Total Dissolved Solids

  • Aluminum
  • Arsenic
  • Magnesium
  • lead
  • Zinc
  • Calcium
  • iron
  • Potassium
  • chloride
  • Copper
  • Chlorine
  • Fluoride
  • Sodium
  • Bicarbonate
  • Insecticide
  • Sulfate
  • Herbicide

Sources of Total Dissolved Solids (TDS)

Total dissolved solids come from many sources, both man-made and natural. Natural sources of total dissolved solids are lakes, springs, plants, rivers and soil. Mineral springs contain water with a high dissolved solids content because they flow through areas of high salinity in rocks. For example, in natural springs, minerals such as calcium, potassium, and magnesium are absorbed as water flows underground.

On the other hand, human activity can also drive the formation of all dissolved solids in water. Herbicides and pesticides can come from farm runoff, lead from aging pipes, and chlorine from water treatment plants. Bottled mineral water sold in supermarkets may contain mineral additives, so total dissolved solids may be intentionally added to the water. Municipal runoff can carry excess minerals to water sources, as can sewage and industrial effluents and salts used in deicer roads.

How is TDS Measured?

TDS (Total Dissolved Solids) represents the total concentration of inorganic and organic substances dissolved in a liquid. It is commonly used as an indicator of water quality and is measured in parts per million (ppm) or milligrams per liter (mg/L).

There are various methods for measuring TDS, and the choice of method depends on the specific application and material of interest. Here are some common techniques for TDS measurements:

 

1.         Conductivity measurement method:

This is the most common way to measure TDS. It is based on the principle that the more dissolved solids in a solution, the higher the conductivity of the solution. The electrical conductivity of liquids is measured with a conductivity meter or conductivity probe. This value is then converted to TDS using a calibration factor specific to the fluid under test.

 

2.         Gravimetry:

In this method, a known amount of liquid sample is evaporated to dryness and the remaining solid residue is weighed. Then convert the weight of the residue to a TDS concentration, considering the dilution factor.

 

3.         Titration:

TDS can also be measured by titration with certain reagents that react with the solute. For example, silver nitrate can be used to precipitate chloride ions and the amount of silver chloride formed is used to calculate TDS.

 

4.         Optical method:

Some optical methods use the light scattering properties of dissolved solids to estimate TDS. By measuring the scattering of light through the sample, the concentration of dissolved solids can be determined.

 

5.         Ion selective electrode:

Ion-selective electrodes can be used to measure the concentration of specific ions in solution, which can be used to calculate the total TDS.

 

6.         Refractive index measurement:

This method is based on the fact that the refractive index of a liquid changes with the concentration of dissolved solids. By measuring the refractive index of the sample, the TDS can be estimated.

It is important to note that TDS measurements provide an overall indication of total dissolved matter in a liquid, but do not identify specific individual components. A more detailed analysis of water quality may require additional testing to determine the specific types of dissolved solids present.

How to Measure TDS

If you have a reverse osmosis system, you can use the following formula to calculate the TDS rejection rate to measure the performance of your reverse osmosis system.

  • Measure the TDS of raw water by immersing the tester probe in a glass of tap water. Record your results.
  • To measure the TDS of RO water, fill a glass with her RO water (from the RO faucet) and dip the tester’s probe into the water. Record your results.
  • Calculate the rejection rate using the following formula.

 

 

Example: Tap TDS = 260 ppm RO TDS = 20 ppm Rejection = [(260 – 20) / 260] x 100 = [240/260] x 100 ≈ (.923) x 100 = 92.3

Note:

Do not test the first tank of RO water if the RO system is new or if the membrane has been replaced. The first tank contains disinfectant and possibly particulates from the new filter, causing erroneous readings.

Why should You Measure Total Dissolved Solids?

Water testing is a great way to check the quality of the water you receive and use for various purposes. Here are some reasons why you should measure water with TDS:

1.         For health purposes

High TDS water is completely safe to drink. However, some substances such as copper and lead can pose health risks.

2.         Flavor

 High TDS concentrations in water change the taste of drinking water. Water can taste salty, bitter, or sulfur, depending on what solids are dissolved in it.

3.         Filter Maintenance

Water filtration systems are adversely affected by high TDS. Regularly test your water purification system to ensure that your filters are working properly and effectively.

4.         Cooking

High TDS levels do not affect your health, but they can change the taste of your food.

5.         Washing

His high TDS concentration in water leaves unsightly stains on dishes. This kind of water can discolor clothing and cause pooling in bathtubs, sinks, and faucets.

6.         Plumbing and Appliances

High levels of dissolved calcium and magnesium salts can cause deposits to form in appliances and pipes, reducing their lifespan.

What happens when TDS Levels in Water are High?

1.         Hardness

High levels of total dissolved solids lead to high concentrations of water, leading to scale buildup in pipes, dirty cookware and even dry hair, as well as reducing the efficiency of kitchen appliances. By checking the TDS of water, you can avoid such troubles in advance.

2.         Flavor and health

High TDS levels change the taste of water, giving it a bitter, salty, metallic taste. A high TDS value also indicates the presence of unwanted minerals that can be harmful to your health.

3.         Pool and spa

Pools and spas require continuous monitoring of water TDS levels to prevent maintenance issues.

Note: A high TDS indicates the presence of toxic substances and contaminants. Hard water is caused by high levels of total dissolved solids. Therefore, a combination of reverse osmosis filters and water softeners should be used to make the water more drinkable.

Health Effects of High TDS in Drinking Water

High TDS values in drinking water can have both positive and negative health effects depending on the substances present and their concentration. Here are some potential health effects of high levels of TDS in drinking water:

1.         Mineral content:

Water with a higher TDS may contain essential minerals such as calcium, magnesium and potassium that can benefit your health. These minerals contribute to the body’s daily absorption of nutrients and support various bodily functions.

 

2.         Taste and Palatability:

High TDS water can have a distinctive flavor that some people may find undesirable. It may taste salty, bitter, or have a metallic aftertaste, resulting in reduced palatability and water use.

 

3.         Gastrointestinal Disorders:

Drinking water with very high TDS levels can cause gastrointestinal problems such as diarrhea and dehydration, especially when the TDS is dominated by harmful substances such as excess sodium or sulfates.

4.         Kidney overload:

Consuming water with a TDS that is too high can put a strain on the kidneys as they have to filter and remove solutes from the body.

5.         Toxic Pollutants:

High TDS readings can indicate the presence of toxic pollutants such as heavy metals (lead, arsenic, cadmium, etc.) and contaminants in the water. Chronic exposure to these substances can lead to serious health problems, including organ damage and an increased risk of cancer.

6.         Cardiovascular Health:

Some studies suggest that long-term consumption of water high in TDS, especially mineral-rich water, may protect against some cardiovascular diseases. However, the evidence is not entirely conclusive.

7.         Dental Health:

Water with a high TDS and high fluoride content can help improve dental health by preventing tooth decay.  However, very high levels of TDS with an excess of fluoride can lead to dental fluorosis, leading to tooth discoloration and damage to tooth enamel.

Is Low TDS Water Harmful?

In general, water with a low TDS value is drinkable and safe for health. In fact, many municipal water supplies and wells supply potable water with low TDS.

The benefits of drinking low-TDS water include a cleaner, refreshing taste and potentially less mineral build-up in water-carrying equipment and plumbing. In addition, low TDS water can be ideal for certain industrial processes or medical applications where the presence of minerals and salts can interfere with desired results.

Note, however, that water with a very low TDS, such as B. distilled or deionized water, may be unfit for normal human consumption for an extended period of time. Drinking water with a TDS close to zero can lead to potential electrolyte imbalances in the body as it lacks important minerals such as calcium, magnesium, potassium and more.

Minerals in water may have health benefits and contribute to the recommended daily allowance. For example, calcium and magnesium are essential for bone health, while potassium is essential for heart function and muscle contraction.

Effect of TDS On Plants

For plants, the effect of TDS on their growth and health can be either positive or negative depending on the concentration and composition of the dissolved solids.

The positive effect of TDS on plants:

  1. Essential Nutrients:

TDS in water often contains essential nutrients such as calcium, magnesium, potassium and other micronutrients. These nutrients are essential for the proper growth and development of plants.

  1. Osmotic Balance:

TDS helps maintain osmotic balance in plant cells. This balance is crucial for the correct uptake and transpiration of water, allowing the plant to regulate its water content and prevent wilting.

  1. Aiding Photosynthesis:

Some dissolved solids such as carbon dioxide and bicarbonates are involved in photosynthesis, the process by which plants convert light energy into chemical energy for growth.

Negative Effects of TDS on Plants:

  1. Toxicity:

High levels of TDS may contain harmful substances such as heavy metals (e.g. lead, mercury) or excess salts (e.g. sodium chloride). The toxic substances can accumulate in plant tissue and cause stunted growth, leaf discoloration, and even plant death.

  1. Reduced Water Uptake:

Extremely high TDS levels can lead to osmotic imbalance, making it difficult for plants to absorb water. This can lead to water stress, wilt and reduced overall vigor.

  1. Soil salinity:

 When water with a high TDS is used for irrigation, excess salts can accumulate in the soil over time, resulting in soil salinity. Salinity negatively affects soil structure, reduces water availability for plants and can make the soil unsuitable for cultivation.

Ways To Reduce Or Eliminate TDS In Water

TDS is reduced in water in the same way that calcium and acid are reduced. Here are some ways to reduce or eliminate TDS in water:

  1. Distillation

The process is evaporation with boiling water to produce steam. The water vapor rises to the cold surface, where it condenses into a liquid. The dispersed salts cannot evaporate and remain in the boiling solution.

  1. Reverse osmosis (RO.)

Reverse osmosis removes TDS by forcing pressurized water through a synthetic membrane. The membrane has microscopic pores that only allow particles smaller than 0.0001 microns to pass through. Because the particles of dispersed metals and salts are large compared to water molecules, water percolates through the membrane leaving behind salts and metals.

  1. Deionization (DI)

Water flows through positive and negative electrodes. The ion selective layer allows positive ions to break away from the water and migrate towards the negative electrode. The usual end result is high purity deionized water. However, the water first goes through a reverse osmosis system to remove non-ionic organic contaminants.