chlorination and its methods

 

Chlorination

Chlorination involves adding a measured amount of chlorine to water to produce a residual sufficient to kill bacteria, viruses, and cysts.

The killing effect of chlorine depends on the pH of the water, temperature, chlorine level.

Methods of Chlorination

The various methods of chlorination in water treatment are:

Plain Chlorination:

The treatment of water with only chlorine is known as plan chlorination.

 It is free from suspended matter and without any prior treatment.

It is typically employed when the water source is already clear and requires no additional steps for sediment or particulate removal.

The main objective of plain chlorination is to disinfect the water, effectively neutralizing or deactivating any harmful microorganisms present.

 

 

Pre-Chlorination:

Pre-chlorination is the process of introducing chlorine to untreated raw water before any other treatment procedures take place.

This method serves a dual purpose: first, it aids in enhancing coagulation by oxidizing specific compounds, facilitating the formation of larger, settleable flocs during subsequent coagulation and flocculation processes. Second, pre-chlorination assists in eliminating taste, odor, and color issues by oxidizing organic compounds responsible for these characteristics.

Post-Chlorination:

Post-chlorination involves the addition of chlorine to treated water after all other treatment stages, such as coagulation, sedimentation, filtration, and initial disinfection, have been completed.

Its primary role is to provide a final dose of chlorine to maintain a residual disinfectant in the water throughout the distribution system.

This ensures the destruction of any remaining microorganisms and safeguards against potential contamination. Post-chlorination typically requires a chlorine dosage in the range of 0.25-5.0 mg/liter to achieve a combined residual chlorine concentration of 0.1-0.2 mg/liter.

Double or Multiple Chlorinations:

Double or multiple chlorinations involve both pre-chlorination and post-chlorination processes.

This approach is typically employed when the raw water source is heavily contaminated and contains a significant concentration of bacterial life.

By utilizing both pre-chlorination to address initial contamination and post-chlorination for residual disinfection, this method effectively ensures the comprehensive treatment of highly polluted water sources.

Break Point Chlorination:

Break Point chlorination is a technique used to determine the optimal amount of chlorine required to achieve the desired level of residual chlorine in water.

By identifying the breakpoint, this method helps water treatment facilities ascertain the precise quantity of chlorine necessary to ensure effective disinfection while preventing excessive chlorine use, which can lead to undesirable disinfection by-products.

 

 

Super Chlorination:

Super chlorination involves the deliberate addition of chlorine to water beyond the breakpoint stage, often implemented at the conclusion of the filtration process. This approach is typically adopted in response to the outbreak of waterborne diseases or when there is a need for a heightened level of disinfection.

However, it is essential to note that after super chlorination, it becomes imperative to remove excess chlorine using an appropriate de chlorination method before the treated water is supplied to consumers.

This precaution helps prevent any potential adverse effects associated with elevated chlorine levels in the drinking water.

Advantages and disadvantages of chlorination of water

Advantages of Chlorination of Water

Kills harmful and pathogenic microorganisms.

Prevents waterborne diseases.

Maintains water quality during distribution.

Provides residual protection.

Cost-effective water treatment method.

Disadvantages of Chlorination of Water

Unpleasant taste and odour.

Formation of potentially harmful disinfection byproducts.

Allergic reactions in some individuals.

Corrosive to certain materials and equipment.

Limited effectiveness against some parasites and viruses.