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Chlorination

Author/Compiled by
Raju Shrestha (Environment and Public Health Organization (ENPHO))
Bipin Dangol (Environment and Public Health Organization (ENPHO))
Dorothee Spuhler (seecon international gmbh)
Executive Summary

Water disinfection by chlorination was massively introduced in the early twentieth century. It set off a technological revolution in water treatment and complemented the known and used process of filtration. In addition to destroying harmful microorganisms, chlorination also reduces the amount of iron, manganese and hydrogen sulphide in water. Chemical disinfection using chlorine has the benefits of being relatively quick, simple, and cheap and allows a residual amount of chlorine to remain in the water to provide some protection against recontamination.

Advantages
Simple, inexpensive and reliable technique
Effectively kills bacteria and viruses
Provides residual chlorine for some protection against re-contamination
Widely available in different countries
Easy to use
Disadvantages
Requires that users purchase chlorine on a continuous basis and may not affordable by very poor people
Does not deactivate parasites like Giardia, cryptosporidium and worm eggs
Taste is unacceptable to some users
Dose is product specific
Availability may be restricted in rural and remote areas
Requires clear water to be most effective
Chlorination of water with high organic matter leads to the risk of toxic disinfection by-products formation
In Out

Freshwater

Drinking Water

Introduction


Chlorination at the household level. Source: CAWST (2009)

Chlorination at the household level. Source: CAWST (2009)

The disinfection of drinking water by adding chlorine is called chlorination. Chlorine was used for the first time in 1850 when John Snow used it in London’s water distribution system to combat cholera. Similarly, American cities like Chicago and New Jersey started to use chlorination around 1908, a step which brought a significant decrease in the number of deaths caused by cholera, typhoid, diarrhoea and hepatitis A. Today, chlorination is used to treat most of drinking water in the world since it is easy, inexpensive and reliable. Chlorine is widely available in different countries with different brand and names.

Chlorination can be achieved by using liquefied chlorine gas, sodium hypochlorite solution or calcium hypochlorite granules and on-site chlorine generators (e.g. WATA).
Chlorine is widely applied for the centralised disinfection of drinking water in municipal water supply systems. International agencies have also been promoting chlorination at household level as effective and simple drinking water treatment option in developing countries.
Chlorine as a household level point of use treatment is available either a solution which is added at doses of one to several drops per litre of water to treat, or as tablets, which will dissolve in the treated water. Aside from these commercial products, water can also be treated at the community level by mixing chlorine in water tanks, wells and household vessels.

How Does it work?

Chlorine tablets and PIYUSH, a 0.5% chlorine solution commercialised in Nepal. Source: The WaterGeeks and ENPHO

Chlorine tablets and PIYUSH, a 0.5% chlorine solution commercialised in Nepal. Source: The WaterGeeks and ENPHO

When chlorine is added to water, the chemical element dissolves and forms radicals. These kill pathogens such as bacteria and viruses by breaking the chemical bonds in their molecules or by attacking the cells of the microorganisms.
The different radicals and ions formed during chlorination destroy many bacteria and viruses, but also oxidise some organic matter, dissolve colours and destroy chloramines, toxic products derived from ammonia. It takes about 30 minutes to do this work and make water safe to drink.


Use of Chlorine

The correct amount of chlorine solution must be used. If the concentration of chlorine is inadequate the solution may fail to destroy all the harmful micro-organisms and if in excess, health may be adversely affected. Only an appropriate amount of chlorine can destroy most of harmful micro-organisms and provide a safe amount of residual chlorine. Chlorine that does not combine with other components and remains in the water is called “Free Residual Chlorine” (FRC). FRC makes sure that water which has been treated by chlorination will not get recontaminated when being transported or stored. According to WHO guidelines, the FRC concentration in drinking water should be between 0.2 to 0.5 mg/L.
 

Effectiveness

Very Effective For:

Somewhat Effective For:

Not Effective For:

  • Bacteria
  • Viruses
  • Most Protozoa
  • Helminths
  • Cryptosporidium
  • Turbidity
  • Chemicals
  • Taste, smell, colour

Source: CAWST (2009)

Chlorine disinfection of drinking water is limited for the protozoan pathogens (in particular cryptosporidium) and some viruses (WHO 1996). Turbidity can protect microorganisms from disinfection. Further, when the natural organic matter (NOM) of the water is high, this can lead to the formation of disinfection by-products (DBPs) such as halogenated organic molecules, mainly trihalomethanes (THM), some of which are potentially hazardous. However, the risks to health from these by-products are extremely small in comparison with the risks associated with inadequate disinfection, and disinfection should not be compromised in attempting to control DBPs (WHO 1996; WHO 2006). In 1991, the International Agency for Research on Cancer evaluated the carcinogenic potential of chlorinated drinking water. IARC concluded, that „there is inadequate evidence for the carcinogenicity of chlorinated drinking-water in humans“. However, for water containing large amounts of organics, the formation of carcinogenic halogenated disinfection products derived from the organic matter attacked by the chlorine is extremely high – it is therefore recommended to use pre-filtration (e.g. slow sand filtration or bio-sand filtration).

How to treat water with chlorine tablets. Source: IFRC (2008)

How to treat water with chlorine tablets. Source: IFRC (2008)

Applicability

Chlorination is very suitable for places where people are directly drinking water from bacterial contaminated water sources but where other contamination (e.g. natural organic matter, arsenic) are not of concern.
It is socially acceptable by general public for purifying water because of easy handling, cost effectiveness as well as good removal of microbial organism in drinking water. It is most commonly used for water disinfection during emergencies (IFRC 2008; CDC/USAID 2008; WHO n.y.). However, a constant supply of chlorine must be guaranteed.
 

Library references

Chlorine

Factsheet on chlorine in general.

CAWST (2009): (= Household Water Treatment and Safe Storage Fact Sheets – Simplified ). Alberta: Center for Affordable Water and Sanitation Technology (CAWST) URL [Accessed: 01.04.2010]

Filtration & Chlorination Systems

Introduction to filtration and chlorination systems at the household level.

CDC/USAID (2009): (= CDC Household Water Treatment Options in Developing Countries Factsheets ). New York: Center for Disease Control and Prevention (CDC) and United States Agency for International Development (USAID) URL [Accessed: 01.04.2010]

Household water treatment and safe storage in emergencies

This document is intended as a general manual on household water treatment and storage in emergencies. Methods of treatment but also promotion are presented, including factsheets, a decision tree and very comprehensive illustrations.

IFRC (2008): pdf presentation. Geneva: International Federation of Red Cross and Red Crescent Societies (IFRC) URL [Accessed: 23.04.2012]

Guidelines for Drinking-Water Quality, Second Edition

This volume of the WHO guidelines for drinking-water quality explains how guideline values for drinking-water contaminants are to be used, defines the criteria used to select the various chemical, physical, microbiological, and radiological contaminants included in the report, describes the approaches used in deriving guideline values, and presents, in the form of brief monographs, critical reviews and evaluations of the effects on human health of the substances or contaminants examined.

WHO (1996): (= Health Criteria and Other Supporting Information - Second Edition , 2 ). Geneva: World Health Organization (WHO) URL [Accessed: 31.03.2010]

Guidelines for Drinking-water Quality. FIRST ADDENDUM TO THIRD EDITION

This volume of the Guidelines for Drinking-water Quality explains requirements to ensure drinking-water safety, including minimum procedures and specific guideline values, and how those requirements are intended to be used. The volume also describes the approaches used in deriving the guidelines, including guideline values. It also includes fact sheets on significant microbial and chemical hazards.

WHO (2006): Geneva: World Health Organization (WHO) URL [Accessed: 19.01.2011]
Further Readings

AUTARCON SuMeWa System

Powerpoint presentation of the water purification system implied by AUTARCON. This system uses solar energy to realise mechanical filtration and chlorification of water.

AUTARCON ; (2012): SolarPV Driven-Drinking Water Treatment. Munich:

Chlorine (NaDCC Tablets)

Factsheet on chlorination with NaDCC tablets.

CAWST (2009): (= Household Water Treatment and Safe Storage Fact Sheets – Academic ). Alberta: Center for Affordable Water and Sanitation Technology (CAWST) URL [Accessed: 01.04.2010]

Chlorine (Sodium Hypochlorite)

Factsheet on chlorination with sodium hypochlorite solutions.

CAWST (2009): (= Household Water Treatment and Safe Storage Fact Sheets – Academic ). Alberta: Center for Affordable Water and Sanitation Technology (CAWST) URL [Accessed: 01.04.2010]

Chlorine

Factsheet on chlorine in general.

CAWST (2009): (= Household Water Treatment and Safe Storage Fact Sheets – Simplified ). Alberta: Center for Affordable Water and Sanitation Technology (CAWST) URL [Accessed: 01.04.2010]

HWTS factsheets

Compilation of factsheets on water quality in general and description of different HWTS options such as chlorination, colloidal silver filters, biosand filter, chlorination and SODIS.

DWSS (2007): Department of Water Supply and Sewerage (DWSS) Nepal, United States Agency for International Development (USAID), United Nations Human Settlements Programme (UN-HABITAT), United Nations Children's Fund (UNICEF)

Chlorination

A 16-page factsheet providing information on water quality and household water treatment options. It contains an introductory section, and one on use, advantages, chlorine preparation and chlorination in Nepal.

DWSS (2009): (= Household Water Treatment options Fact Sheet , 6 ). DWSS, UNICEF, UN-HABITAT, USAID & ENPHO

Challenges to the Commercial Viability of Point-of-Use (POU) Water Treatment Systems in Low-Income Settings

This dissertation investigates the commercial viability of point-of-use (POU) water treatment systems (solar treatment, physical treatment and chemical treatment) in lower income settings. Six factors that have helped POU projects approach commercial viability are highlighted, including refining and improving product positioning, leveraging existing health awareness, offering an array of POU options, adapting business practices, finding alternative models of viability, and focusing on key product improvements.

HARRIS, J. ; (2005): Master Thesis. Oxford School of Geography and the Environment Oxford University URL [Accessed: 30.03.2010]

Smart Disinfection Solutions

This booklet, part of the Smart Water Solutions series provides a wide range of methods and products for home water treatment in rural areas.

NWP (2010): Examples of small-scale disinfection products for safe drinking water. (= Smart water solutions ). Amsterdam: KIT Publishers URL [Accessed: 07.07.2010]

Shock Chlorination for Private Water Systems

This paper provides detail information on shock chlorination. It is also available at www.oznet.ksu.edu

POWELL, M ; ROGERS, D.H. ; WILLINGHAM, J.M. ; (2005): Kansas State University URL [Accessed: 20.02.2010]

UNICEF Handbook on Water Quality

This handbook is a comprehensive a new tool to help UNICEF WASH field professionals, but it will also be useful to other UNICEF staff and for partners in government, other external support agencies, NGOs and civil society. The handbook provides an introduction to all aspects of water quality, with a particular focus on the areas most relevant to professionals working in developing countries. It covers the effects of poor water quality, quality monitoring, the protection of water supplies, methods for improving water quality, and building awareness and capacity related to water quality.

UNICEF (2008): New York: United Nations Children's Fund (UNICEF) URL [Accessed: 30.03.2010]

Gender In Water Resource Management Supply and Sanitation. Roles and Realities Revisited

This book investigates how gender is present in the newly emerging principles on the sustainable management of water resources. The book also reviews how these gender specific principles are currently applied in the water supply, sanitation and hygiene sector.

WIJK-SIJBESMA, C. van ; (1998): The Hague: International Water and Sanitation Centre (IRC) URL [Accessed: 30.03.2010]

Guidelines for Drinking-water Quality, Third Edition

This volume of the Guidelines for Drinking-water Quality explains requirements to ensure drinking-water safety, including minimum procedures and specific guideline values, and how those requirements are intended to be used. The volume also describes the approaches used in deriving the guidelines, including guideline values. It includes fact sheets on significant microbial and chemical hazards.

WHO (2008): Third Edition incorporating the First and Second Addenda. Geneva: World Health Organization (WHO) URL [Accessed: 23.04.2012]

Guidelines for Drinking-water Quality, Fourth Edition

This volume of the Guidelines for Drinking-water Quality explains requirements to ensure drinking-water safety, including minimum procedures and specific guideline values, and how those requirements are intended to be used. The volume also describes the approaches used in deriving the guidelines, including guideline values. It includes fact sheets on significant microbial and chemical hazards.

WHO (2011): Geneva: World Health Organization (WHO) URL [Accessed: 08.08.2011]

Source Book of Alternative Technologies for Freshwater Augmentation in Latin America and the Caribbean

The Latin American and Caribbean countries have seen growing pressure on water resources, with increasing demand and costs, for agricultural, domestic and industrial consumption. This has brought about the need to maximize and augment the use of existing or unexploited sources of freshwater. There are many modern and traditional alternative technologies for improving the utility and augmenting the supply of water being employed in various countries, but with limited application elsewhere due to the lack of information transfer among water resources managers and planners. This book was prepared to provide water resource managers and planners, especially in developing countries and in countries with economies in transition, with information on the range of technologies that have been developed and used in the various countries throughout the world.

UNEP (1998): Nairobi: United Nations Environment Programme (UNEP) URL [Accessed: 17.10.2011]

Conservation et Traitement de l Eau a Domicile

This practical guide provides a review of different processing techniques and adequate water conservation at home and is structured around 10 key questions that should be posed before choosing a suitable solution.

DESILLE, D. ; (2013): Paris: Programme Solidarite Eau (PSeau) URL [Accessed: 06.06.2013]
Case Studies

Nepal’s Experiences in Community-Based Water Resource Management

This paper documents WAN and its partners’ work on community-based approaches to water resource management, and attempts to distil important lessons from their experience to inform continued refinement of WAN’s institutional approach to CWRM and inform sector learning.

WAN (2008): (= Fieldwork paper ). Water Aid Nepal (WAN) and End Water Poverty URL [Accessed: 30.03.2010]
Training Material

Linking Technology Choice with Operation and Maintenance in the context of community water supply and sanitation. A reference Document for Planners and Project Staff

This document is addressed to planners and staff of water supply and sanitation projects on household and community level. The reader is guided through the main steps of informed choices regarding the main proven technologies for water supply, purification and water treatment at household and community level. Each technology is described in a small factsheet, regarding its functioning, actors and their roles, the main operation and maintenance (O&M) requirements and problems, which can occur.

BRIKKE, F. ; BREDERO, M. ; (2003): Geneva: World Health Organization and IRC Water and Sanitation Centre URL [Accessed: 30.03.2010]

Chlorine (NaDCC Tablets)

Factsheet on chlorination with NaDCC tablets.

CAWST (2009): (= Household Water Treatment and Safe Storage Fact Sheets – Academic ). Alberta: Center for Affordable Water and Sanitation Technology (CAWST) URL [Accessed: 01.04.2010]

Chlorine (Sodium Hypochlorite)

Factsheet on chlorination with sodium hypochlorite solutions.

CAWST (2009): (= Household Water Treatment and Safe Storage Fact Sheets – Academic ). Alberta: Center for Affordable Water and Sanitation Technology (CAWST) URL [Accessed: 01.04.2010]

Chlorine

Factsheet on chlorine in general.

CAWST (2009): (= Household Water Treatment and Safe Storage Fact Sheets – Simplified ). Alberta: Center for Affordable Water and Sanitation Technology (CAWST) URL [Accessed: 01.04.2010]

HWTS training guideline

This training manual provides information on various household drinking water treatment options. Each description contains an introduction to the technology, its working mechanism, costs, advantages and limitations (Nepali).

DWSS (2008): Nepal: Department of Water Supply and Sewerage (DWSS)

Food and Water in an Emergency

This booklet should support households to prepare them for emergency situation by storing emergency food and water supplies.

FEMA (2004): Federal Emergency Management Agency (FEMA), U.S. Department of Homeland Security and American Red Cross URL [Accessed: 30.03.2010]

Household water treatment and safe storage in emergencies

This document is intended as a general manual on household water treatment and storage in emergencies. Methods of treatment but also promotion are presented, including factsheets, a decision tree and very comprehensive illustrations.

IFRC (2008): pdf presentation. Geneva: International Federation of Red Cross and Red Crescent Societies (IFRC) URL [Accessed: 23.04.2012]

How to measure chlorine residual in water

Many of the most common diseases found in traumatized communities after a disaster or emergency are related to drinking contaminated water. This factsheet concentrates on the problems caused by drinking water contaminated by micro-organisms and their reduction by chlorination.

WHO (2005): (= Technical Notes for Emergencies , 11 ). Geneva: World Health Organization (WHO) URL [Accessed: 31.03.2010]
Awareness Raising Material

Filtration & Chlorination Systems

Introduction to filtration and chlorination systems at the household level.

CDC/USAID (2009): (= CDC Household Water Treatment Options in Developing Countries Factsheets ). New York: Center for Disease Control and Prevention (CDC) and United States Agency for International Development (USAID) URL [Accessed: 01.04.2010]

Flip Chart on HWTS

Flipchart presentation on description of different household water treatment options including introduction, installation and organisation and maintenance procedures of each technology (in Nepali).

DWSS (2007): Nepal: Department of Water Supply and Sewerage (DWSS)

Amoeba and Water

This children’s book provides information on safe drinking water, ways of water contamination, simple HWTS options presented in attractive illustrations and simple languages so that school children can easily understand them.

ENPHO (2007): Kathmandu and New York: Environment and Public Health Organization (ENPHO) and United Nations Children's Fund (UNICEF) URL [Accessed: 09.04.2010]

Combating Waterborne Diseases at the Household Level

This document is divided into three main parts. The first part contains an introduction to the topic and depicts some possible, simple techniques for treating water at the household level. The second part describes the possibility of collaborating to fight against waterborne diseases and the last part presents again some low-cost solutions.

WHO (2007): The International Network to Promote Household Water Treatment and Safe Storage. Geneva: World Health Organisation (WHO) URL [Accessed: 11.10.2010]

Alternative Versions to

No Structure Described.