Definition of Chlorination: Everything About Chlorine & Water

 

Chlorination is the process of adding chlorine or chlorine compounds to water to disinfect it by killing harmful microorganisms like bacteria, viruses, and other pathogens. This is a crucial step in water treatment to ensure water safety for drinking, bathing, and other uses.

Chlorine works by breaking down the cell walls of microorganisms, preventing them from reproducing and causing illness. This process plays a vital role in maintaining public health, particularly in urban water systems, as it helps prevent waterborne diseases such as cholera and typhoid.

What Is Chlorine?

Chlorine is a chemical element with the symbol Cl and atomic number 17. It belongs to the halogen group (Group 17) of the periodic table and is one of the most reactive nonmetals. Here’s a breakdown of what chlorine is and its significance:

Basic Characteristics

  • Atomic Structure: Chlorine has 17 protons and 17 electrons, with its outermost electron shell containing seven electrons, making it highly reactive as it seeks to gain one electron to complete its octet.
  • Physical Appearance: Chlorine is a yellow-green gas at room temperature, with a pungent and distinct odor.
  • State: It exists as a diatomic molecule (Cl₂) in its natural gaseous state.
  • Occurrence: While highly reactive, chlorine does not occur freely in nature. Instead, it is found in compounds, most commonly as sodium chloride (NaCl) in seawater and salt deposits.

Reactivity

Chlorine is a highly reactive element due to its high electronegativity (3.16 on the Pauling scale) and strong oxidizing potential. This reactivity makes it a powerful disinfectant and industrial chemical.

  • Chemical Behavior: Chlorine readily reacts with metals, nonmetals, and organic compounds.
  • Disinfectant: In aqueous solutions, chlorine reacts to form hypochlorous acid (HOCl) and hypochlorite ions (OCl⁻), which kill microorganisms by disrupting their cellular functions.

Applications

  1. Water Treatment: Chlorine is extensively used to disinfect drinking water, swimming pools, and wastewater to control pathogens.
  2. Industrial Use: It plays a key role in the production of plastics (e.g., PVC), solvents, and pesticides.
  3. Medical Field: Chlorine-based compounds are used in antiseptics, pharmaceuticals, and as sterilizing agents.

Health and Environmental Impact

  • Benefits: Chlorine’s disinfecting properties have revolutionized public health by reducing waterborne diseases like cholera and typhoid.
  • Risks: Exposure to high concentrations of chlorine gas can cause respiratory irritation, while improper handling of chlorine-based compounds can lead to the formation of harmful byproducts, such as trihalomethanes (THMs).

Does chlorine have a smell?

Yes, chlorine has a distinct smell, often described as sharp or bleach-like. However, what many people identify as the "chlorine smell" is not pure chlorine itself. Instead, it’s usually caused by chloramines, which are compounds formed when chlorine reacts with organic matter such as sweat, oils, or other impurities in the water. This is common in swimming pools or poorly ventilated areas with treated water.

When chlorine levels are properly balanced, the odor is minimal or nonexistent. A strong chlorine smell may indicate an imbalance, often due to insufficient free chlorine levels and excessive combined chlorine (chloramines).

How to Remove Chlorine Smell?

If you encounter a noticeable chlorine smell, here are ways to reduce or eliminate it on drinking water systems :

  1. Aeration: Allow water to sit exposed to air. Chlorine naturally dissipates over time, especially in open containers.
  2. Boiling Water: Boiling removes chlorine faster by speeding up its evaporation. This works well for small quantities of water.
  3. Activated Carbon Filters: Install filters in your home system or use filtered pitchers. These effectively remove chlorine and its odor from drinking water.
  4. UV Treatment: Ultraviolet light systems can neutralize chlorine in water systems, making them odor-free.

By maintaining proper chlorine levels and treating water effectively, you can minimize or eliminate chlorine smells while ensuring the water remains safe.

Discover our Chlorine Dosage Calculator

The Dosatron smartphone app includes a chlorine dosage calculation feature. This tool assists users in accurately determining the appropriate chlorine dosing for their specific applications, ensuring effective water treatment and disinfection.

The app provides step-by-step guidance to help you perform all your chlorination calculations and share them with anyone you want.

Is Chlorinated Water Safe to Drink?

Yes, chlorinated water is safe to drink when the chlorine levels remain within the guidelines set by health authorities, such as the U.S. Environmental Protection Agency (EPA).

The EPA limits chlorine in drinking water to 4 milligrams per liter, ensuring it effectively disinfects while minimizing any risks. Studies from institutions like Harvard University confirm that chlorination has significantly reduced the spread of diseases like dysentery and typhoid.

While some people might notice a slight taste or odor, these are not harmful, and any remaining chlorine can be removed using activated carbon filters.

Types of Chlorination

Chlorination is not a one-size-fits-all process; different methods are used depending on the water's source and treatment goals:

Pre-Chlorination

Chlorine is added early in the treatment process to control biological growth, reduce algae, and improve taste and odor.

Post-Chlorination

Applied after filtration, this step ensures microbial safety before water is distributed.

Breakpoint Chlorination

A process that adds enough chlorine to satisfy chemical demands, achieving effective disinfection and eliminating ammonia.

Shock Chlorination

A high dose of chlorine used in emergencies to clean wells, tanks, or systems.

Super Chlorination

Involves using high doses of chlorine to eliminate severe contamination, followed by dechlorination to reduce chlorine to safe levels.

Chloramination

Combines chlorine and ammonia to create chloramines, a long-lasting disinfectant with fewer byproducts.

Dechlorination

Removes excess chlorine to prepare water for industrial, environmental, or specific domestic uses.

Each type has unique applications, ensuring effective water treatment tailored to specific conditions. 

What Does Free Chlorine Mean?

Free chlorine is the portion of chlorine available to disinfect water and kill microorganisms. It exists in three forms:

  • Hypochlorous Acid (HOCl): The most effective form, dominant in water with a pH of 6–7.
  • Hypochlorite Ion (OCl⁻): Less effective, found at higher pH levels (above 8).
  • Dissolved Chlorine Gas (Cl₂): Rare in water treatment due to pH adjustments.

Free chlorine is critical for disinfection, contrasting with combined chlorine, which forms when chlorine reacts with organic matter or ammonia.

Free vs. Total Chlorine

Free chlorine is the active disinfectant, while total chlorine measures both free and combined chlorine. Combined chlorine, or chloramines, is less effective and can cause irritation and odor. Maintaining proper free chlorine levels ensures effective water disinfection. If combined chlorine levels rise, shocking the water with a strong oxidizer can restore balance.

Discover our Low Flow Chlorinator

The D14WL chlorinator helps to keep your drinking water clean and safe by killing harmful bacteria and viruses. This is important for protecting your health and the health of your family.

The D14WL chlorinator helps to protect you from harmful bacteria and viruses by killing them in the water before they reach your faucet. This is especially important for people who have compromised immune systems, such as young children and the elderly.

The D14WL chlorinator can save you money on chemicals by using a more efficient dosing system. This means that you will need to use less chlorine to keep your water clean and safe.

The D14WL chlorinator contributes to environmental stewardship. By optimizing chlorine dosing through its efficient system, it minimizes the need for excessive chemical and energy usage. This reduction in consumption not only saves you money but also translates into a decreased environmental footprint.

In addition to its direct benefits for individual consumers, the Dosatron D14WL Low Flow Chlorinator contributes to the overall well-being of communities. By consistently maintaining the safety and quality of drinking water, this chlorinator helps prevent waterborne diseases from spreading through public water systems.