Water is not only a powerful drink but also a universal solvent. As such, it has the ability to dissolve and absorb molecules from a number of substances. These dissolved particles in a volume of water are the total dissolved solids (TDS) level. TDS has two forms, organic and inorganic. Understanding and calculating the total dissolved solids present in your drinking water will define its overall quality.
Total Dissolved Solids, also known as TDS, are inorganic compounds found in water, such as salts, heavy metals, and some traces of organic compounds dissolved in water. In simple words, it represents the total concentration of dissolved substances in water. The inorganic salt commonly found in TDS is categorized into two: (1) cations, which include calcium, magnesium, potassium, and sodium, and (2) anions, which include carbonates, nitrates, bicarbonates, chlorides, and sulfates. As such, cations are positively charged ions, and anions are negatively charged ions.
Some of these compounds or substances can be essential in life, including the organic matter that is sometimes naturally present in water and the environment. In fact, the TDS level is a good indicator of whether or not drinking water is suitable for human consumption. It also tests whether a certain water quality needs a rigid filtration system or is highly contaminated. But, it can be harmful when taken more than the desired amount needed by the body. This is because the total dissolved solids present in water are among the leading causes of turbidity and sediments in drinking water. When left unfiltered, total dissolved solids can be the cause of various diseases.
Total dissolved solids (TDS) measure the combined total of organic and inorganic substances contained in a liquid. This includes anything present in water other than the pure H20 molecules. These solids are primarily minerals, salts, and organic matter that can be a general indicator of water quality.
So, in this article, we'll get into detail about TDS, TDS in Drinking water, TDS meters, the composition of TDS (and how they contaminate the water quality), and the reasons why TDS ends up in dissolved water. We will also talk about the Acceptable TDS Level in Drinking Water, Factors Affecting TDS, and several treatments and mitigation processes to employ and lessen the negative effects of TDS in water.
Understanding the Total Dissolved Solids (TDS)
All sources of natural water include dissolved substances and minerals. These minerals are measured as the total dissolved solids or TDS. It is comprised of natural minerals, which are inorganic salts. Some of these are potassium, calcium, magnesium, chlorides, bicarbonates, and sulfates. In addition, it can have contaminants like heavy metals, which are low in concentrations. When you measure the TDS, the presence of heavy metals cannot be exactly determined.
In the water, TDS is identified as parts per million (ppm) or mg/L. Since TDS does not risk people's health, the EPA has not identified a TDS limit. However, it suggests that the drinking water only has a level of up to 500 ppm.
If the water has above 500 ppm, they can notice deposits on the water, salty taste, or staining. These effects are not harmful. However, it can be noticeable.
The TDS in Drinking Water
The TDS in drinking water comes from natural water sources, sewage, urban runoff, industrial wastewater and chemicals used in the water treatment process, and the hardware or piping used to distribute water. Natural environment features like salt deposits, mineral springs, seawater intrusion, and carbonate deposits in the US brought higher TDS.
Other sources may include anti-skid materials, salts used for road de-icing, stormwater, agricultural runoff, water treatment chemicals, and point/non-point wastewater discharges.
In general, the total dissolved solids concentration is the total cations (positively charged) and anions (negatively charged) ions in the water. Thus, the total dissolved solids test qualitatively measures the number of dissolved ions but does not tell us the nature or ion relationships.
In addition, the test does not provide us insight into the specific water quality issues, such as Elevated Hardness (mineral content in water), Salty Taste, or Corrosiveness (also called aggressive water, which is how water dissolves with other materials).
Therefore, the total dissolved solids test is used as an indicator test to determine the general quality of the water. The sources of total dissolved solids can include all of the dissolved cations and anions. Still, the following table can be used to generalize the relationship of TDS to water quality problems.
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Cations combined with Carbonates. |
Associated with hardness, scale formation, bitter taste |
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Cations combined with Chloride |
Salty or brackish taste increases corrosivity |
Total Dissolved Solids (TDS) Meters
Many people are conscious of TDS meters. It measures the water’s electrical conductivity, which can be connected to the amount of TDS. Meanwhile, a TDS meter can’t directly measure heavy metal contaminants like arsenic and lead. It does not indicate whether or not the water filter works properly to decrease this type of contaminant.
The normal TDS level ranges from 50 ppm to 1,000 ppm. On the other hand, the National Sanitary Foundation (NSF) International does not certify the use of the TDS meters.
What Composes Total Dissolved Solids and How Do They Contaminate Our Water Supply?
Different substances comprise the total dissolved solids in drinking water. As a natural flora of water and the environment, bacteria and viruses can be found in total dissolved solids. These are the organic compounds found in drinking water.
Chemicals in the water and water supply include heavy metals, salts, and pharmaceutical drugs caused by human waste materials, contaminating the water and water supply.
Water that comes from springs, lakes, and waterfalls has natural microorganisms and salts. This will, in turn, go to public water treatment and is stored for supplying the community.
Not only that but also phytoplankton, one of the natural floras of water, can sometimes be found. Phytoplankton is a type of microscopic plant that drifts off to different bodies of water.
Sometimes, chemicals such as iron, potassium, sodium, and other chemicals known to man are present in drinking water. These chemicals are caused by human waste products that contaminate these water sources.
Not to mention the volatile organic compounds, they also pollute the water by leaking through the water supply by soil.
Volatile organic compounds, also known as VOCs, are rapidly evaporating compounds chemically designed for specific use at home, school, and anywhere you can think of.
Other Reasons Why Solids End Up Dissolved in Water
Mineral springs contain high levels of dissolved solids because the water has flowed through a region where the rocks have a high salt content. For instance, the Prairie provinces in the US tend to have high levels of dissolved solids because of high amounts of calcium and magnesium in the ground.
These minerals can also come from human activities. Agricultural and urban runoff can carry excess minerals into water sources, as can wastewater discharges, industrial wastewater, and salt used to de-ice roads.
What is the Acceptable Total Dissolved Solids (TDS) Level in Drinking Water
Total Dissolved Solids (TDS) are measured in milligrams per unit volume of water (mg/L) and are also referred to as parts per million (ppm). For drinking water, the maximum concentration level set by EPA is 500 mg/L.
Factors Affecting TDS
High Flow Rates
When we talk about TDS concentrations, the flow rate of a body of water can be a major factor. Fast-running water can have large-sized and more sediment. Heavy rains can pick up clay, sand, silt, and other particles like tire particles, leaves, and soil. Moreover, a change in the flow rate can affect total suspended solids. If the current water's direction or speed increases, the particulate substance from the bottom sediments may be suspended.
Soil Erosion
Soil erosion is due to the troubles on the surface of the land. Illegal logging, forest fires, mining, and construction can cause it. The particles of eroded soil can be carried via the stormwater into the surface water. With this, it can increase the level of TDS and TSS in the water.
Urban Runoff
When the storm comes, the debris and solid particles from the commercial or residential areas can be washed away into the streams. Due to the large amount of pavement in cities, there is an increase in infiltration and increase in velocity. The natural settling areas are removed. Through the storm, the sediments are carried into rivers and creeks.
Overflow of the Septic and Wastewater System
The particles from the wastewater treatment plants can also contribute to the suspension of solids in the stream. The wastewater from residential areas contains human waste, food residue, and other materials that we flush into the drains. Most of the solids are already eliminated from the water at the plant. However, not everything is eliminated during the treatment.
Rotting Animals and Plants
As animals and plants decay, there are suspended organic particles which can be released. This can all contribute to TDS and TSS concentration in the drinking water.
Bottom-Feeding Fish
Bottom-feeding fish like carp can disturb the sediments since they tend to remove vegetation. Indeed, these sediments can add to TDS and TSS.
Why Should You Measure the TDS Levels in Your Water?
Numerous water supplies exceed this level. TDS levels exceeding 1000mg/L are generally considered unfit for human consumption. A high level of TDS is an indicator of potential concerns and appeals for further investigation.
Most often, high levels of TDS are caused by potassium, chlorides, and sodium. These ions have little or no short-term effects, but toxic ions (lead arsenic, cadmium, nitrate, and others) may also be dissolved in the water.
Even the best water purification systems on the market require monitoring for TDS to ensure the filters and membranes are effectively removing unwanted particles and bacteria from your water. Here are other applications of the importance of the TDS level:
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Taste / Health
High TDS would result in an undesirable taste, which could be salty, bitter, or metallic. The EPA’s recommended maximum level of TDS in water is 500mg/L (500ppm).
Health Considerations
In past studies, inverse relationships were reported in TDS concentrations on drinking water and coronary heart disease, cancer, cardiovascular heart disease, and arteriosclerotic heart disease. There is an inverse correlation between TDS levels and total mortality rates.
In an Australian study, it has been found that mortality rates are high in a community with higher levels of soluble calcium, sulfate, magnesium, chloride, and fluoride. This is in comparison to a community with lower levels.
Other Considerations
The dissolved solids present in the water can affect its taste. In a study, a panel of tasters rated the palatability of drinking water. It is excellent if the TDS is less than 300 mg/L. It is good if the TDS is between 300 to 600 mg/L. It is fair if the TDS is between 600 to 900 mg/L. The water tastes poor if the TDS is between 900 to 1,200 mg/L. Finally, the water tastes unacceptable if the TDS is greater than 1,200 mg/L.
If the water has a shallow TDS level, it can also be unacceptable due to its bland and flat taste.
Apart from the water’s palatability, some components of TDS can affect the encrustation and corrosion of the water distribution systems. Examples of this are sulfates, chlorides, calcium, carbonates, and magnesium. If there are high TDS levels above 500 mg/L, it can result in excessive scaling in the water heater, boilers, pipes, and other appliances inside the house. With scaling, it can shorten the lifespan of your appliances.
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Filter performance
Test your water to make sure the reverse osmosis or other types of water filter or water purification system has a high rejection rate and know when to change your filter (or membrane) cartridges.
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Hardness (and Water Softeners)
High TDS point out the Hard water, which causes scale build-up in pipes and valves. This eventually restricts performance.
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Aquariums / Aquaculture
A constant level of minerals is needed for aquatic life. The water in an aquarium or tank must have the same TDS levels and pH as the fish and reef’s original habitat.
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Hydroponics
TDS is the best measurement of the nutrient concentration in a hydroponic solution.
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Pools and Spas
TDS levels must be monitored to prevent maintenance problems
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Commercial / Industrial
High TDS levels could prevent the functions of certain applications, such as boilers and cooling towers, food and water production, etc.
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Colloidal silver water
TDS levels must be controlled before making colloidal silver.
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Coffee and Food Service
For a truly great cup of coffee, proper TDS levels must be maintained.
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Car Washing and Window Cleaning
It gives the best result when cleaning.
Options for the Treatment of TDS
NSF International has published a certified reverse osmosis system that can reduce the TDS level in the water. This can be extremely helpful as you identify the suitable unit to install in your house.
Indeed, NSF International does not approve of the use of the TDS meters. However, it does certify the treatment systems to reduce contaminants like heavy metals.
The system must be effective at reducing the contaminants which the manufacturers claim. There must be structural integrity to ensure that the treatment system or filter does not leak. Also, there is material safety testing to see that it can identify the impurities eliminated when the filter is not in use. Finally, the product must be labeled accurately to ensure that it does not contain any misleading information.
Analytical Methods and Treatment Technology
In water supplies, the most commonly used analysis method is through the measurement of specific conductivity that determines the presence of ions in water. These measurements are converted to TDS values by a factor that determines the water type.
TDS are not essentially removed with the use of conventional water treatment techniques. The chemicals added during the traditional treatment of water can generally increase the concentration of the TDS. Some treatment techniques like softening through lime-soda ash plus sodium exchange zeolite can increase TDS concentration. The process of demineralization is needed for TDS removal.
Indeed, demineralization is available to decrease the TDS levels, but its high cost can be a major constraint. Electrodialysis and reverse osmosis can be economical methods to remove TDS in public water supplies.
What are the Ways to Remove Total Dissolved Solids in Drinking Water?
These chemicals are absorbed by the soils that eventually contaminate the water supplies. Though some of the total dissolved solids are natural floras, filtration and purification are effective ways to remove these chemicals from our drinking water.
To give you a short water filtration and purification process, the water coming from the water sources goes to the public water treatment to undergo filtering. In this process, large particles or substances are filtered out and removed from the water.
Sometimes, in this process, small particles can get through the filters. This is still causing turbidity in drinking water and is not yet safe to be consumed. Once it undergoes filtration, it is then purified using certain methods.
Depending on the company or water treatment facility, some use chemicals, radiation or micro-filtration, and chlorination to remove microscopic particles still present in water.
In removing dissolved solids in drinking water with the use of chemicals as reagents, these reagents help filter these substances out. Chemicals such as aluminum sulfate and liquid chlorine are used.
These chemicals are flocculating chemicals that help in water filtration. What they do is that they clump the particles together until they form a larger particle.
These flocks can then be easily removed or filtered out. Some chemicals used are fluorosilicic acid, sodium silicofluoride, and sodium fluoride. These chemicals give a unique reaction.
These chemicals give off energy by creating heat. When these chemicals are combined with water, they burn, thus killing the bacteria, viruses, protozoans, and other organic microorganisms found in water.
Once the drinking water is filtered off the impurities, it still has a strange taste that is not drinkable yet. This was when calcium hydroxide was added to water.
Calcium hydroxide, also known as lime water, is an automated chemical that does not affect alkalinity and water acidity. So, it makes it safe to drink and will have the taste of natural water.
While some water treatment facilities use chemical reagents to filter and purify drinking, some public water treatment facilities use filtration, chlorination, and UltraViolet radiation to purify drinking water.
This treatment starts when the water coming from water sources goes to the water supply for particles to be filtered out. Once filtered, it will remain in the water supply for chlorination.
When chlorine is added, it will remain in the water storage until the smell of chlorine cannot be detected. Since chlorine is a derivative of salt and sodium, sometimes it cannot be easily dissolved. When the chlorination process is done, it goes to a special process where radiation is involved.
With the help of Ultraviolet rays, water is then radiated to ensure that the remaining chlorine substances will be dissolved, and the microorganisms that made it through the filtration and chlorination process are killed.
These residues turn into sediments found at the bottom of the water and cause turbidity in the water.
The Correlation Between pH Levels and TDS Levels
Total Dissolved Solids (TDS) correlate positively with conductivity and affect pH. This means that the higher the TDS, the higher the conductivity and the lower the pH, towards acidity. Furthermore, in the presence of dissolved solids, the taste of the water may evidently change. By standard, surface water has a pH value between 6.5 and 8.5, while groundwater typically has a pH between 6.0 and 8.5. However, still, the water source can differ from one source to another.
There are a lot of human-induced activities that pose huge threats to the pH levels of the water sources within the vicinity. In a specific instance, industrial operations and vehicles release harmful substances such as sulfur dioxide and nitrogen oxides —which, in turn, produce acid rain. This, in effect, affects the overall pH levels of nearby water sources. Another factor is chemical pollution which can potentially transform a large body of water into an acidic one. This is because harmful chemicals can diffuse into the water through illegal discharges or irresponsible wastewater treatment processes.
Ultimately, an alteration of the pH levels in water can generate a number of consequences —good or bad. For example, in the environment, living things, including plants and animals alike, are put in dangerous (sometimes lethal) situations due to acidification. Moreover, marine and aquatic life are also put in extreme danger since they are very sensitive to changes in water temperature and composition. This, in particular, can affect the food supply, as well as the biodiversity of marine life.
Guidelines for pH: Canada Vs. United States
CANADA
The guidelines for pH levels on water vary from city to city, as well as country to country. In Canada, the pH of drinking water should be between 7.0 and 10.5. This is in resonance with the Canadian Guidelines for Drinking Water Quality. Meanwhile, a province in Canada called Saskatchewan has its own pH level guidelines. According to the Saskatchewan Drinking Water Standards and Objectives, the pH of drinking water should be between 6.5 and 9.0.
UNITED STATES
In the United States, pH level is considered the next water standard, second to TDS. In accordance with the Secondary Maximum Contaminant Level, the pH levels should range between 6.5 and 8.5. Moreover, the Environmental Protection Agency has released a statement saying that the noticeable effects of a pH level that is less than 6.5. This pH level denotes a bitter-tasting and metallic aftertaste in water. Likewise, a pH level of 8.5, generates noticeable effects such as slippery texture, soda-like taste, and small deposits.
Conclusion
TDS is an essential factor in the water quality of drinking water. It is an indicator of whether the water is too turbid or lacks the essential minerals needed by the body. An elevated total dissolved concentration (TDS) level does not mean that the water becomes a health hazard. But, this doesn't mean the water may have aesthetic problems or cause nuisance problems.
The problems may be concerned with staining, taste, or precipitation. Concerning trace metals, higher TDS levels may indicate that they are present in the water. Another important thing to keep in mind, the water may be corrosive if the TDS level is very low. The corrosive waters may leak toxic metals from the household plumbing. Given this situation, it may pose a health hazard as well. Dealing with this kind of water, hard water can be annoying. The initial recommendation is to get your water tested and determine your water's general quality and chemistry. Do this before consuming or installing your water treatment system.
To conclude, ensuring that your drinking water quality is clean, safe, and reliable should be a basic standard. Through TDS, as well as other factors, we are able to determine whether or not our water source is fit for day-to-day consumption.
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