Potable Water: Sources, Purification Methods, Water Treatment

The term “potable water” refers to water that is safe for human consumption, which means that it can either be consumed directly or utilized in the preparation of food. The word suggests that the water is fit for human consumption in addition to being risk-free. To be considered drinkable, water must be devoid of any objectionable smells, tastes, or colors.

Potable Water
Potable Water

Potable water has low concentrations of both dissolved salts and microorganisms. Because it has dissolved substances, we cannot consider it “pure” water. It is also known as drinking water and originates above and below ground from various sources. This water has been treated to concentrations compliant with state and federal regulations for human consumption.

Characteristics of Potable Water

  • The aqueous solution ought to exhibit a lack of hue and possess clarity, devoid of any turbidity.
  • The absence of any discernible odour in water is desirable, although a slight presence of chlorine odour within acceptable limits is permissible.
  • It is recommended that the suspended/insoluble solid impurities be maintained at low levels.
  • It is recommended that potable water contain minerals, micronutrients, and salts.
  • Potable water ought to be free from microorganisms such as Escherichia coli. This is an imperative necessity as microorganisms possess pathogenic properties and have the potential to induce perilous illnesses. Potable water should not contain any microorganisms.

What Causes Water to Be Unfit for Consumption?

The categorization of potable water contamination by the World Health Organization (WHO) encompasses organic, inorganic, radiological, and microbiological factors, and incorporates assessments of taste, odor, and visual characteristics for determining acceptability.

  • Organic contaminants refer to a class of carbon-based chemicals, such as solvents and pesticides, that can be introduced into the environment through agricultural runoff or industrial discharge. They have the potential to cause a variety of significant health issues, ranging from cancer to disruption of endocrine function.
  • Radiological hazards encompass radon, cesium, plutonium, and uranium. Radon is the primary cause of lung cancer among individuals who do not smoke in North America, and it is also the primary environmental cause of cancer-related deaths.
  • Inorganic pollutants, comprising of mineral acids, inorganic salts, metals, cyanides, and sulfates, exhibit long-lasting characteristics in the environment. The presence of heavy metals in certain foods can lead to neurological complications in humans, particularly in the vulnerable populations of children and fetuses. Additionally, these metals have the potential to accumulate within the food chain. The ingestion of arsenic has been linked to various adverse health outcomes such as cancer, skin lesions, cardiovascular disease, diabetes, and cognitive impairment. The occurrence of algal blooms, which are caused by the presence of nutrients such as phosphorus and nitrogen, can potentially lead to the introduction of cyanotoxins into drinking water.
  • Waterborne pathogens, such as bacteria, viruses, protozoa, and parasites, are commonly introduced to water through fecal matter. These pathogens have the potential to cause a variety of illnesses, ranging from mild gastroenteritis to severe conditions such as diarrhea, dysentery, hepatitis, typhoid fever, cholera, and cryptosporidiosis. A significant number of individuals are afflicted with tropical diseases transmitted through water, such as trachoma, which is recognized as the primary cause of avoidable blindness.
  • In addition, there exist certain substances known as “emerging contaminants” or “contaminants of emerging environmental concern” that pose a threat to drinking water. These substances comprise pharmaceuticals that are introduced into water bodies via sewage and runoff from livestock operations.
  • The presence of suspended particles in water, also known as turbidity, can result in an unsatisfactory taste, odor, or appearance of the water. The potential harm of turbid water is contingent upon the composition of the suspended material, as opposed to solely its aesthetic qualities.

To ensure efficient treatment of potable water, it is crucial to conduct a thorough analysis of the source water and subsequently customize the treatment process to meet the specific water conditions and standards.

Methods of Producing Potable Water

Water purification is the removal of unwanted chemicals, biological pollutants, and suspended solids from water. Some methods of producing potable water are discussed here:

Harvesting Rainwater

  • Potable water is made from rainwater. We get our drinking water from rainwater. Rainwater has very low quantities of dissolved chemicals, indicating that it is fresh water. Rainwater collects in rivers, lakes, and underground reservoirs.
  • We can gather both groundwater and surface water. We can collect rainwater from underground rocks. This is referred to as groundwater. We can also collect surface water, which is rainwater collected from lakes and rivers.
  • Surface water can evaporate. Lakes and rivers, that contain water on the surface, can dry out in hot weather. This means that in hotter climates and locations, drinking water is primarily derived from groundwater.
  • Rainwater is filtered through filter beds to remove insoluble solids. Small, insoluble solids are removed from fresh water using sand filters.

The Sterilization Process

Rainwater must be disinfected, sterilized. This is due to the presence of bacteria in freshwater.

  • The first step in the process is filtration: Filtration is the first step in the process of producing drinkable water. This is accomplished by running clean water through filter beds to remove any large particles such as stones or small particles such as sand.
  • Sterilizing agents are then employed: After the filtration procedure, sterilizing chemicals are employed to treat the rainwater. These sterilizing agents include chlorine gas, ozone, and UV light. These kill bacteria to reduce levels to a safe level.

Using Seawater

Surface and groundwater may be in short supply. In some severely hot countries, there may not be enough surface or groundwater to produce potable water.

  • Instead, seawater can be used. Seawater can be utilized to make drinkable water rather than rainwater. This water is really salty. We must eliminate the salt from the water.
  • Salt can be removed using reverse osmosis. We can eliminate the salt from saltwater through a procedure known as reverse osmosis. This is accomplished by a membrane. When seawater is subjected to high pressure, water molecules are forced through the barrier while salt is left behind.
  • It could be costly to use seawater. Using seawater to make drinkable water is an extremely expensive method. This is because reverse osmosis requires a lot of energy to achieve high pressure.
  • The process of distillation of saltwater will result in desalination. Seawater is heated to more than 100°C during distillation. The generated water vapor has no salt. It condenses to produce pure water by desalination. This is an expensive operation because enormous amounts of water must be boiled.

Standards for Potable Water

  • In order to be classified as potable water must adhere to specific standards and guidelines established by the governing body of the respective nation. The regulatory bodies of governments establish guidelines regarding the permissible levels of particular substances in drinking water.
  • Prescribed Concentrations and Values (PCV) are commonly used terminologies in the United Kingdom. As per the guidelines set by the UK government, the permissible level of Fluoride/PCV in drinking water is 1.5mg/L. The PCV values for Enterococci and E. Coli in potable water are both zero per 100mL, indicating the absence of said microbes in the water.
  • It is recommended that the pH level of drinking water falls within the range of 6.5-9.5, as it is deemed optimal to avoid extreme acidity or alkalinity.

Modern Water Treatments Process

Modern technology has been developed based on older treatments. Aerobic processes have traditionally been the primary method for treating wastewater, especially for sewage and other waste streams that contain high levels of organic or biodegradable materials. Aerobic processes involve microorganisms that flourish in oxygenated water and are capable of breaking down organic contaminants while eliminating nitrates.

Membrane Aerated Biofilm Reactor (MABR)

  • The membrane aerated biofilm reactor (MABR) is the latest and most effective method of aerobic treatment. It requires significantly less energy for aeration, which is the most energy-intensive phase of biological treatment, up to 90% less in fact.
  • The MABR system facilitates simultaneous nitrification-denitrification within a single tank that contains a spirally wound, air-permeable membrane. Aeration occurs at a pressure close to atmospheric pressure.
  • MABR is a technology that stands out for its superior effluent quality and energy efficiency. It can be used to upgrade existing plants or in compact, pre-packaged systems that are ideal for decentralized treatment approaches.

Reverse osmosis (RO)

Membrane-based water purification techniques, such as reverse osmosis filtration, have made remarkable progress since the 1970s and 1980s.

  • Reverse osmosis (RO) utilizes modern filtration techniques by applying pressure to water and passing it through a semi-permeable membrane that selectively blocks unwanted solutes at the molecular level.
  • Desalination is a common method of using RO for producing drinkable water. Desalination plants in modern times are responsible for producing approximately 50% of Israel’s drinkable water. Desalination has become more cost-effective due to increased recovery rates and decreased energy and chemical consumption. Smart Packaged options for desalination are now available, which can be easily scaled and deployed, making them suitable for decentralization.

Anaerobic digestion

  • Anaerobic digestion is a biological treatment process that effectively removes organic material and trace organic contaminants (TOCs) generated by human activity. This process relies on microbes that thrive in the absence of oxygen.
  • Toxic organic compounds (TOCs) can accumulate in organisms through processes such as biomagnification and bioaccumulation. This accumulation can lead to irreversible harm in both humans and animals by disrupting their endocrine systems and causing tumors.
  • Microorganisms break down organic compounds during the anaerobic digestion process, resulting in the creation of a biogas that is predominantly composed of methane. It is possible to install waste-to-energy systems that collect methane and convert it into usable energy.

Ion exchange

It is a widely used chemical process that involves exchanging unwanted dissolved ions with similarly charged ions. This process is extensively used for potabilization, including water softening, demineralization, dealkalization, deionization, and disinfection. Ion exchange resins that are designed to target specific contaminants such as nitrates, perchlorate, and uranium have gained popularity for the production of potable water.

Methods of Processing Wastewater to Potable Water

There are two basic methods for turning wastewater to drinkable water that includes:

Direct potable reuse (DPR) and indirect potable reuse (IPR)

Direct potable reuse: Without the need of an environmental buffer, cleansed wastewater is immediately added to the raw water supply supplying a water treatment plant in direct potable reuse.

Indirect potable reuse: Indirect potable reuse is releasing treated wastewater into a strategic environmental source, such as an aquifer or reservoir, for a predetermined amount of time before it is withdrawn for use in drinkable products. In 1962, the Montebello Forebay project of the Los Angeles County Sanitation District featured one of the earliest applications of indirect potable water reuse.

Because pathogens and chemical pollutants are present in higher amounts in source water, potable water reuse necessitates careful monitoring.

Treatment of Wastewater

Urban lifestyles result in the production of wastewater. The majority of the world’s wastewater is produced by people due to the urbanization of lifestyles and the industrialization of activities. Sewage, dishwashing liquid, and field wastewater are a few examples.

Treatment is necessary for wastewater. Before it can be released back into the environment, the wastewater that has been deposited in sewers needs to be treated. We must purge the water of any potentially hazardous chemicals.

It is necessary to get rid of the organic materials, germs, and chemicals. To be more specific, we need to clear wastewater of excessive concentrations of organic matter, bacteria that are dangerous to humans, and chemicals. It is possible that these made their way into the water system as a result of industrial processes, sewage , or agricultural practices.

Treatment of Sewage

Treatment is necessary for wastewater. As we have seen, the wastewater that is collected in sewers needs to be treated before it can be released back into the natural environment. This can be accomplished by following the four steps mentioned in this approach.

Examination of sewage: Before the wastewater can be treated effectively, any large particles that may be present in the water must first be filtered out. Screening is the technique that is used to accomplish this goal, since it is responsible for removing grit and larger particles.

Sedimentation: After that, we can let the wastewater settle in a tank for some time. Because of this, any particles that are very heavy will be able to sink to the bottom of the tank. Sludge settles to the bottom of the container, while effluent rises to the top as a result of this process, which is referred to as sedimentation.

Bacterial treatment: After that, we will be able to treat the effluent that is produced by the wastewater with bacteria. These bacteria will set in motion the course of aerobic digestion, which eliminates any pathogens that may be present in the water.

Anaerobic digestion: After the effluent has been cleaned, the next step is to treat the sludge that has been left over. Methane gas is produced as a byproduct of the process of anaerobic digestion, which accomplishes this goal. The gas known as methane can be used as a source of energy.

Home Remedies to Purify Water

There are times when different natural disasters can compromise the drinkability of water, or it may be the time of year when you are camping with your friends and it is difficult to find drinkable water.

We might have to purify water for ourselves. There are ways to treat water locally which are discussed here:

Boiling The Water

The water is often boiled as the first step in the purification process. Microorganisms can be eradicated by boiling for an adequate amount of time, which may also remove some potentially harmful chemical pollutants.
In order to bring the water to a boil, you have a number of different options for heating it. These may consist of a burner for a stovetop, a microwave, or an electric kettle.

Using Chlorine Bleach

If you are unable to boil the water, you can eliminate any bacteria that may be present in the water by using unscented bleach from the household supply store. Chlorine, which is found in bleach, is what is utilized to render potable water supplies that are provided by municipalities; this type of water is referred to as chlorinated water. If the water is hazy, you should pass it through a filter made of cloth before treating it.

Using Iodine

It is common practice to sell iodine solutions, crystals, or pills to hikers so that they may quickly add the substance to their water bottles while they are out on a hike. Iodine is a simple compound that has the ability to eradicate bacteria and viruses, despite the fact that it is ineffective against more resilient species such as cryptosporidium. The aftertaste that it leaves in the water is a drawback to using it.

Using a Filter

Bacteria and protozoa can be removed from the water through the use of water purification filters.
Certain chemicals and “off” tastes can be removed by using a carbon filter. Be sure to carefully read the directions that come with your water purification filter in order to ensure that you are using it properly and to have an understanding of the contaminants that it will and will not remove. You will have to take precautions to prevent the filter from becoming clogged by the sediment in the water.

Using UV Water Filter

Bacteria, protozoa, and viruses can all be eradicated from water with the help of ultraviolet (UV) purifying lights. There have been reports of UV lamps being integrated into bottles of water, however the most frequent form factor is a battery-operated pen-shaped light.

The light won’t be able to disinfect the inside of solid particles, therefore filter the water with a towel before employing this approach to get rid of them. If the water is turbid, it may also be ineffective.

Differences Between Potable Water and Pure Water

Let us compare the potable water and pure water.

Potable waterPure Water
Potable water refers to water that has undergone filtration and sterilization processes to ensure its safety for human consumption. Potable water is deemed suitable for human consumption.Pure water refers to water that has undergone a purification process to eliminate any impurities present. This substance is not suitable for consumption.
Potable water is also known as drinking water.An example of pure water is distilled water, typically used in laboratories.
It contains some minerals and nutrients that are important for the healthy metabolism of the body, not simply H2O.Pure water has nothing but H2O. No minerals and nutrients. Frequent consumption will lead to deficiency disorders.
Potable water can be used for cooking, drinking, and manufacturing beverages.Pure water is used in: Laboratories to conduct experiments, Clean microchips, and Semiconductor manufacturing.
Surface water treated with chlorine or ozone or subjected to UV treatments will produce potable water.Pure water is a result of an evaporation-condensation process called distillation.
A good conductor of electricity because of dispersed charged ions (Na+, H+, OH, Ca2+, Cl).Due to the limited presence of dispersed ions, specifically H+ and OH, this substance exhibits a notably low electrical conductivity. The majority of distilled water is present in the form of H2O molecules.

References

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  • Abul Hussam, Potable Water: Nature and Purification https://doi.org/10.1016/B978-0-444-59395-5.00011-X
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About Author

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Kabita Sharma

Kabita Sharma, a Central Department of Chemistry graduate, is a young enthusiast interested in exploring nature's intricate chemistry. Her focus areas include organic chemistry, drug design, chemical biology, computational chemistry, and natural products. Her goal is to improve the comprehension of chemistry among a diverse audience through writing.

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