water purification method

Methods of Water Treatment

Since hydrogen and oxygen atoms are closely linked, water is known to be clean by nature. However, other substances including organic matter, minerals, chemicals, and man-made pollution must coexist alongside water supplies throughout the world. This results in a non-drinkable solution since it may include harmful bacteria, viruses, and other pathogens. Fortunately, humankind has been able to create a variety of water treatment techniques to ensure the safety of our water supply. All of these make untreated water fit for human consumption, even though some of them are ineffective on a larger scale.

How Water Treatment Facilities Safeguard Water

To supply their communities with clean drinking water, public drinking water systems employ a variety of water treatment techniques. Coagulation, flocculation, sedimentation, filtration, and disinfection are common water treatment processes used in public water systems. Depending on the technology of the plant and the type of water that needs to be treated, there may be subtle variations in the water treatment process at different places. However, the fundamental ideas remain the same. Let’s discuss the standard methods for treating water.

  1. Coagulation

The initial stage of water treatment is coagulation. When water is raw or untreated, positively charged chemicals like liquid aluminium sulfate, alum, and/or polymer are added to create coagulation. The negative charge of dirt and other dissolved particles in the water is balanced by the positive charge. The resulting mixture makes the dirt coagulate or clump together in the water.

When this happens, the particles and chemicals bond together to create somewhat larger particles. After that, the clusters of dirt particles join forces to form flocs, which are then simple to remove via filtration or settling.

  1. Flocculation

Coagulation is followed by flocculation. Water is gently mixed to generate larger, heavier particles known as flocs through a process called flocculation. In order to aid in the formation of the flocs, water treatment facilities often add extra chemicals during this phase.

  1. Sedimentation

After treatment, flocs and water are deposited in basins for sedimentation. The heavier floc particles sink to the bottom because the water travels slowly in this area. Sludge is a floc that collects at the bottom of a container. This continues in drying lagoons. In direct filtration, the floc is only eliminated through filtration; there is no sedimentation step.

Water treatment facilities employ sedimentation as one of their processes for separating particulates from water. Because flocs are heavier than water, they sink to the bottom of the water during sedimentation.

  1. Filtration

Filtration is the process of passing water through a filter designed to remove impurities from the water. These filters are made of gravel, sand, or occasionally crushed anthracite. Filtration collects contaminants that float on water and increases the power of disinfection. Backwashing is a method used to clean filters on a regular basis. The clean water on top is filtered to remove further solids from the water after the flocs have sunk to the bottom of the tank. The pure water goes through filters constructed of various materials and with various pore sizes during the filtration process (such as sand, gravel, and charcoal). These filters eliminate germs and dissolved contaminants such as dust, chemicals, parasites, bacteria, and viruses. Bad odours are also eliminated by activated carbon filters.

In addition to or instead of conventional filtration, water treatment facilities may use an approach known as ultrafiltration. Water passes through a filter membrane with incredibly small pores during ultrafiltration. This filter only permits water and other small molecules to pass through (such as salts and tiny, charged molecules).

Reverse osmosis is another filtration technique that takes out extra impurities from water. When preparing recycled water (also known as reused water) or salt water for drinking, water treatment facilities often use reverse osmosis.

  1. Disinfection

To remove pathogenic bacteria, parasites, and viruses, water is disinfected before entering the distribution system. Since chlorine is so powerful, it is also used.

Water treatment facilities may add one or more chemical disinfectants (such as chlorine, chloramine, or chlorine dioxide) after the water has been filtered to eliminate any lingering parasites, bacteria, or viruses. Water treatment facilities make sure the water has low concentrations of the chemical disinfectant before it leaves the facility to help keep water safe as it goes to residences and commercial establishments. The remaining disinfectant eliminates bacteria present in the pipes leading from the water treatment facility to your tap.

Water treatment facilities can disinfect water using ultraviolet (UV) radiation in addition to or without adding chlorine, chloramine, or chlorine dioxide. Although ultraviolet (UV) light or ozone are effective disinfectants in water treatment facilities, they do not continue to destroy germs when water passes through pipes to reach your tap.

  1. Sludge Drying

After they have been captured and removed from water by sedimentation and filtering, solids are transferred to drying lagoons.

  1. Fluoridation

In order to minimize tooth cavities, local water supplies use fluoridation treatments to optimize the concentration of free fluoride ions. After disinfection, water treatment facilities add fluoride and modify the pH of the water. By adjusting the pH, you can enhance flavour, lessen pipe corrosion (or breakdown), and ensure that chemical disinfectants continue to kill germs as the water passes through the pipes. The appropriate quantity of fluoride in water helps prevent cavities and keeps teeth strong.

  1. pH Correction

Lime and filtered water are blended to modify pH levels. Additionally, this stabilizes naturally soft water to reduce corrosion in plumbing and water distribution systems.

The way each community treats its water varies

Depending on the quality of the source water that enters the treatment facility, water may be treated differently in different communities. Most frequently, either surface water or groundwater is the water that enters the treatment facility. Because lakes, rivers, and streams contain more sediment (sand, clay, silt, and other soil particles), bacteria, pollutants, and toxins than groundwater does, surface water often needs more treatment and filtration than ground water.

Certain substances (such as nitrates), radionuclides (small radioactive particles), or poisons may be present in some water systems (such as those made by cyanobacteria). Water treatment may also include specialized techniques to reduce or eliminate certain impurities. Check out our Water, Sanitation & Hygiene course for more information.

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