The Importance of Water Treatment Chemicals in Public Health

Water treatment is a process for improving water quality. A fundamental human right is access to clean, safe drinking water.  Water treatment helps to remove impurities and hazardous substances from the water. Maintaining an appropriate pH value is essential for drinking water.

1. Coagulation

The negative charge of dirt and other dissolved materials is balanced by adding positively charged chemicals to the water.

 These components include iron and some salts.

The dosage or amount of coagulant should be carefully determined to achieve visible floc formation. The amount of coagulant should be such that the turbidity of the water is reduced to a level of 10 to 25 p.p.m.

The following six are the common coagulants used for coagulation

  • Aluminium sulphate
  • Chlorinated chopperas
  • Ferrous sulphate and lime
  • Magnesium carbonate
  • Polyelectrolytes
  • Sodium aluminate

2. Flocculation

Flocculation uses a variety of formation methods and chemicals to create flocs.  A commonly used flocculant is a long-chain organic polymer such as polyacrylamide, which utilizes two mechanisms to flocculate coagulated waste particles: electrostatic attraction and bridging. These charged forms of the polymer reinforce the mechanisms that attract and bridge the coagulated particles, enhancing and improving the flocculation process.

 The coagulated precipitate absorbs most of the suspended solids from the water and is then filtered off by passing the mixture generally through a coarse sand filter or sometimes through a mixture of sand and granulated anthracite (high carbon, low volatile coal).

Aluminum hydroxide is also commonly used as a flocculant, although there are concerns about possible health effects and mishandling led to a serious poisoning incident in Camelford in the south west of the UK in 1988 when the coagulant was discharged directly into the final treated water storage tank.

Today’s common synthetic polymers include PolyDADMAC, a man-made polymer. 

These polymers have a high molecular weight and form very stable and easy to remove flocs,

3. Sedimentation

Sedimentation is a component of water filtration in our circulation system.

The term “sedimentation“ is well known from sewage treatment plant technology.

As soon as large flocs have formed, they have to be settled, which is done in a process called sedimentation. For sedimentation, the water is left in the tank for several hours. Sludge is the substance that gathers at the bottom of the tank and is taken out for disposal.

4. Filtration

During filtration, solids are separated from a liquid. During the water treatment process, the water is run through beds of sand and gravel to remove any particles that did not separate in the sedimentation tank.

 Rapid gravity filters (Figure 5.7) with a flow rate of 4–8 cubic meters per square meter of filter area per hour (4–8 m–3 m–2 h–1) are often used.

In water treatment, filtration is generally used after coagulation and sedimentation to:

  • Remove residual suspended solids
  • Reduce turbidity and improve water clarity of the water
  • Remove bacteria, viruses and other pollutants 
  • Remove residual dirt and impurities

Water treatment often employs the following filtration types:

  • Activated carbon
  • Filtration with granular media (e.g. sand, gravel, activated carbon)
  •  Biological filtration (e.g. trickling filters, biological activated carbon)
  •  Membrane filtration (e.g. reverse osmosis, ultrafiltration, microfiltration)

5. Disinfection

In this step, all remaining parasites, bacteria and viruses must be eliminated. This can be done by adding one or more chemical disinfectants such as chlorine or chlorine dioxide.

Disinfection is usually achieved by various methods, including

  • Chlorination (addition of chlorine or hypochlorite)
  •  Ceramic filtration
  •  Distillation
  •  Chlorine dioxide disinfection
  • Ozonization (addition of ozone)
  •  Disinfection with ultraviolet (UV) light

The guidelines of the World Health Organization (WHO, 2003) recommend a maximum residual chlorine content of 5 mg l–1 of water. After 30 minutes of contact, the residual chlorine level should be no less than 0.5 mg l-1 of water.

WHY….?

Water is fundamental to life and is required for daily survival.We use it for a lot of things, like cleaning, cooking, and drinking. What happens, though, if the water you are consuming is tainted? Because of the potentially catastrophic consequences for your health, adequate water treatment is essential for maintaining public health.

By using chemicals for water treatment, bacteria, viruses, and other pathogens are eliminated, preventing the spread of illnesses that are contracted through contact with water. These include dysentery, typhoid, and cholera.

Improving Public Health: Access to safe drinking water is essential for maintaining one’s health. Water treatment chemicals contribute to public health goals by improving overall health and well-being and reducing the incidence of waterborne illnesses.

Water system maintenance costs can be reduced with adequate water treatment.

Chemicals used in water treatment lessen the risk of contracting diseases that are spread by water, which lowers the chance of epidemics.

Understanding the significance of proper water treatment and how it helps to stop the spread of waterborne illnesses is crucial for maintaining public health. We can enhance public health and save the environment for future generations by funding the creation of innovative technologies and making sure that everyone has access to clean drinking water.

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