Purifying Water Pollution: Innovative Methods For A Cleaner Future

Water is essential for human consumption and various other purposes, and it is important to confirm that your water has been purified or treated before drinking. Water purification methods can be classified into two categories: physical methods and chemical methods. Physical methods include boiling, distillation, and filtration, while chemical methods include chlorination and flocculation. Boiling is a cheap and effective way to purify water, but it may not be sufficient for water sources with high levels of pollutants or particulate matter. Chlorination is another effective method, but it can form harmful disinfection byproducts if consumed in large quantities. Other methods of water purification include sedimentation, reverse osmosis, and UV purification. It is important to note that water sources and distribution channels may render your water unsafe, and alternative sources of clean water may be necessary in certain situations.

Methods to Purify Water Pollution

Boiling water

To purify water through boiling, it is important to first collect water from a safe source. Water from a natural source, such as a river or lake, may look clean but can be filled with harmful organisms. It is recommended to collect water from areas with moving water, and to avoid stagnant water, which is a breeding ground for insects, bacteria, and viruses. The water should be collected in a clean container that has preferably been disinfected prior to use.

Once the water has been collected, it should be heated to the boiling point. This can be done using a campfire, propane stove, biogas cooking stove, or an electric kettle. Reaching the boiling point is important, as it ensures the full inactivation of pathogens. At higher altitudes, water boils at lower temperatures, so it is recommended to boil water for longer. After boiling, the water should be left covered to cool before drinking.

While boiling is an effective method of water purification, it has some limitations. Boiling does not remove turbidity, chemicals (such as arsenic), taste, smell, or colour from water. It is also not suitable for water with high amounts of iron, calcium, or chlorine. Therefore, in areas with high levels of pollutants or particulate matter, other methods such as filtration or chemical treatment may be needed in addition to or prior to boiling.

Chlorination

The process of chlorination involves adding a measured amount of chlorine to water supplies to eliminate harmful microorganisms, bacteria, viruses, and other pathogens that could pose serious health risks. Chlorine is typically added to water using chemical feed systems to inject liquid sodium hypochlorite (bleach) solution or added as gaseous chlorine. Chlorine can also be applied by generating it on-site using electrolysis or by using chlorine tablets, which are cheap and effective. When using chlorine tablets, it is important to apply them to heated water, as they dissolve well in water that is at 21°C or higher. Chlorine was first discovered in Sweden in 1744 and has been used for water treatment for over a century.

The main objective of chlorination is to disinfect the water and maintain chlorine residuals that will remain in the water as it travels through the distribution system. Chlorine is a powerful disinfectant that can kill harmful microorganisms, including bacteria, viruses, and parasites that can cause waterborne illnesses. Chlorination can also be used to control biological growth, remove iron and manganese, improve taste and odours, control algae growth, and remove the colour from the water.

There are different types of chlorination processes, including pre-chlorination, post-chlorination, and super chlorination. Pre-chlorination is the process of introducing chlorine to untreated raw water before any other treatment procedures, enhancing coagulation and eliminating taste, odour, and colour issues. Post-chlorination, on the other hand, involves adding chlorine to treated water after all other treatment stages to provide a final dose of chlorine and maintain a residual disinfectant. Super chlorination involves the deliberate addition of chlorine beyond the breakpoint stage, typically in response to the outbreak of waterborne diseases or when a heightened level of disinfection is required.

While chlorination is a popular and effective method of water purification, it is important to note that it can form disinfection by-products (DBPs) when chlorine reacts with organic matter in water. These DBPs can be harmful if consumed in large quantities, so controlling the pH level during chlorination is crucial to minimise their levels. Additionally, some people may have allergies or sensitivities to chlorine, and it may not be effective against all types of microbes, such as protozoan cysts.

Distillation

The boiling chamber in a distillation unit is where the water enters and is heated to a rolling boil, causing evaporation and steam production. The steam then moves to the condensing coils or chamber, where it is cooled and converted back into liquid water. Finally, the purified water is collected in a storage tank or container. Some distillation units also have volatile gas vents to eliminate organic chemicals with lower boiling points than water, ensuring the purity of the final product.

Filtration

Water filtration is a process that separates impurities and contaminants from water by passing it through a medium that traps or absorbs them. It is one of the most cost-effective and commonly used methods to purify water. Filtration uses both chemical and physical processes to remove compounds and make water safe for human consumption. It is also a simple and fast way to remove both large and small dangerous compounds that may aggregate inside water, which are known for causing waterborne diseases.

There are two types of filtration: gravity type (e.g. Paterson’s Filter) and pressure type (Candy’s Filter). The rate of filtration is about 100-400 L/m2/hr. The sand granular size (diameter mm) is 0.2-0.3. The pretreatment of water includes sedimentation and then filter cleaning by scraping. It does not require prior water storage.

One of the most common types of filters used to purify water is the rapid sand filter. The rapid sand filtration process purifies water in five steps. Firstly, iron or aluminium salts, such as polymers, aluminium sulfate, ferric sulfate, or ferric chloride, are added to the water during the coagulation process. Secondly, these substances, which have a positive charge, are known as coagulants. Coagulation eliminates impurities and other particles present in water. Thirdly, raw water is treated with a chemical coagulant such as alum (5-40 mg/L). Fourthly, depending upon the turbidity and colour, the doses of alum range from 5-40 mg or more per litre. Finally, alum and other chemicals are violently mixed in the water to form tiny sticky particles known as "floc" that attract dirt particles.

Small-scale water is also purified by filtration through ceramic filters such as the Pasteur Chamberland filter, Berkefeld Filter and Katadyn Filter. The essential part of a filter is the filter candles, which are made of porcelain or infusorial earth and have the potential to accumulate bacteria and impurities. They can eliminate bacteria found in drinking water; however, viruses that pass through the filter are not.

Reverse osmosis

The process typically begins with pre-filters, including sediment filters that remove larger particles like sediment, chlorine, and organic matter, which could damage or clog the RO membrane. This initial step ensures that the water is adequately prepared for the detailed filtration to follow. High pressure is then applied to push the water through the semi-permeable membrane, which features tiny pores (about 0.0001 microns) that only allow water molecules to pass through while blocking and removing dissolved salts, chemicals, and microorganisms.

The purified water, termed the permeate, is then collected in a storage tank for later use. When there is a demand for water, it passes through a post-filter to remove any residual taste before being delivered through a dedicated faucet, providing clean, safe drinking water. Reverse osmosis systems are highly effective at removing dissolved contaminants that are invisible to the naked eye but potentially harmful if consumed. They can remove contaminants such as heavy metals (including lead and mercury), chlorine and chlorine by-products, bacteria, parasites, and trace pharmaceuticals.

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