Preventing Recontamination

Compiled by:
Beat Stauffer (seecon international gmbh)

Executive Summary

Recontamination of clean or already treated water is a common problem in many countries. On the household level, there are several simple methods to avoid it, for example hand washing with soap before touching any water facilities. However, piped networks must be also maintained and operated in a proper way by educated technicians. Residual chlorination is the most common measure to prevent regrowth or recontamination. There are several contamination sources such as permeation, leaching or microbiological growth inside the water pipes.

In Out

Freshwater, Drinking Water

Freshwater, Drinking Water

Introduction

Most drinking water around the world, from almost every water source, should be considered unsafe (see also pathogens and contaminants) unless it is treated and stored properly. Even where piped water is delivered to the household, point-of-use treatment by boiling or other methods is widespread—and for good reason. Intermittent service, degraded infrastructure, or unreliable water treatment forces many people to question the quality of water they drink. Increasing scarcity of high-quality water has led to significant and growing demand for products and services that provide safer drinking water, particularly in the developing world, where water supply infrastructure has not kept pace with economic growth and population shifts (BROWN et al. n.y.).

Preventing Recontamination at the Household Level

Adapted from WHO (1997)

Why?

The principal health risk (see also health risk management) associated with household water storage is the ease of recontamination during transport and storage, particularly where the members of a family or community do not all follow good hygiene practices. The most crucial factor for preventing recontamination or regrowth at the household level is safe storage. In the case the risk of recontamination or regrowth is high, residual chlorination or POU water purification is required. After the purification, water should be tested before it is consumed.

Preventing Recontamination in Water Distribution Networks

Below, there is a description about common processes and problems in piped distribution systems and how to prevent them.

Microbiological Growth and Regrowth

The threat of excessive microbial growth along the interior walls of drinking water distribution pipes is a common problem. The development of an organic bacterial community, also commonly known as biofilm, is composed of microorganisms and their secretions. It is present in almost every water distribution system, and when uncontrolled may present a threat to public health.

Chlorination: Chlorinating the drinking water supply (residual chlorination) is the method usually used to control biofilm growth. In most cases, maintaining the normal amount of chlorine used to disinfect drinking water will control this problem (WQHC 2012).

Chlorine Residual Testing: The presence of residual chlorine concentrations in drinking water indicates that (CDC n.y.):

  1. A sufficient amount of chlorine was added initially to the water to inactivate the bacteria and some viruses that cause diarrhoeal disease.
  2. That the water is protected from recontamination during storage. The presence of free residual chlorine in drinking water is correlated with the absence of disease-causing organisms, and thus is a measure of the potability of water.

According to WHO guidelines, the FRC (Free Residual Chlorine) concentration in drinking water should be between 0.2 to 0.5 mg/L (WHO 2006). Read more about it in the factsheet about centralised chlorination.

Permeation

Permeation in water distribution systems occurs when contaminants external to the pipe materials and non-metallic joints pass through these materials into the drinking water. Permeation is generally associated with plastic non-metallic pipes (see also water distribution pipes). The contaminants that are most commonly found to permeate plastic pipes are organic chemicals that are lipophilic and non-polar, such as highly volatile hydrocarbons and organic solvents, because they can readily diffuse through the plastic pipe matrix, alter the plastic material, and migrate into the water within the pipe (NATIONAL RESEARCH COUNCIL 2006). But also the intrusion of polluted groundwater or leakages from sewer systems can cause recontamination (see also leakage control). This is particularly a problem when intermittent water supply is common.

Leaching

All materials in the water distribution system undergo reactions that introduce substances to the water via a process known as "leaching." Pipes, fittings, linings, and other materials used in joining or sealing pipes leach at least some substances to water through corrosion, dissolution, diffusion, or detachment. Internal coatings in water storage facilities can also leach substances. Most known substances that leach into water from materials in the distribution system do not appear to pose a public health threat due the fact they are non-toxic, present only at trace levels, or are in a form unlikely to cause health problems. However, taste and odour complaints are possible (NATIONAL RESEARCH COUNCIL 2006).

To prevent leaching as well as permeation problems, operation and maintenance of drinking water networks (see also leakage control) and sewer lines is important, as well as groundwater and soil quality.

Lead poisoning

Exposure to lead causes a variety of health effects, and affects children in particular. Water is rarely an important source of lead exposure except where lead pipes, for instance in old buildings, are common (see also water distribution pipes). Removal of old pipes is costly but the most effective measure to reduce lead exposure from water (WHO 1993).

Costs

To prevent recontamination in large distribution systems, qualified labourers, technical equipment and an organised management are needed. These raise costs for such a system but prevent health costs.

Applicability

The described problems and sources of contamination can be found everywhere where water is stored, distributed and transported (human powered or motorised). It is important that people know how to handle (treated) water so that recontamination can be avoided and human health is protected.

Advantages

  • No recontamination, fewer health problems
  • Techniques to prevent recontamination on household level are very easy and low cost

Disadvantages

  • If there is no education it is difficult to avoid recontamination
  • Communities must be willing to support essential activities and education programmes

References Library

BROWN, J.; OUTLAW, T.; CLASEN, T.; WU, J.; SOBSEY, M.D. (n.y.): Safe Water for All - Harnessing the Private Sector to Reach the Underserved. Wahsington, D.C.: International Finance Corporation (IFC). URL [Accessed: 04.04.2012]. PDF

CDC (Editor) (n.y.): Chlorine Residual Testing. Atlanta: Centers for Disease Control and Prevention. URL [Accessed: 18.07.2012]. PDF

NATIONAL RESEARCH COUNCIL (U.S.) (Editor) (2006): Drinking Water Distribution Systems: Assessing and Reducing Risks. Washington, D.C.: National Academy of Sciences. URL [Accessed: 10.04.2012].

WQHC (Editor) (2012): Safe Water Delivered Safely. Water Quality and Health Council (WQHC). URL [Accessed: 10.04.2012]. PDF

WHO (Editor) (1993): Water-related Diseases. In: HAVELAAR, A. H.; MELSE, J. M. (2003): Quantifying Public Health Risk in the WHO Guidelines for Drinking Water Quality. Geneva, 49-50. URL [Accessed: 10.04.2012].

WHO (Editor) (1997): Guidelines for Drinking-water Quality. Second Edition, Volume 3. Surveillance and Control of Community Supplies. Geneva: World Health Organization (WHO). URL [Accessed: 04.04.2012]. PDF

WHO (Editor) (2006): Guidelines for Drinking-water Quality. FIRST ADDENDUM TO THIRD EDITION. Geneva: World Health Organization (WHO). URL [Accessed: 19.01.2011]. PDF

Further Readings Library

Reference icon

AINSWORTH, R. (2004): Safe Piped Water: Managing Microbial Water Quality in Piped Distribution. Geneva: World Health Organization (WHO). URL [Accessed: 24.03.2011]. PDF

This review looks at the factors affecting the presence and growth of microorganisms in piped networks, and the practices of water supply organisations that can directly or indirectly influence their presence and growth. This review is intended for policymakers but it is also relevant to engineers and scientists responsible for water supply planning, operations and monitoring.


Reference icon

BROWN, J.; OUTLAW, T.; CLASEN, T.; WU, J.; SOBSEY, M.D. (n.y.): Safe Water for All - Harnessing the Private Sector to Reach the Underserved. Wahsington, D.C.: International Finance Corporation (IFC). URL [Accessed: 04.04.2012]. PDF

This report is built on research conducted in Kenya, Uganda, China, and India. These countries represent emerging markets that offer promising investment opportunities for increasing access to clean, safe drinking water.


Reference icon

CDC (Editor) (n.y.): Chlorine Residual Testing. Atlanta: Centers for Disease Control and Prevention. URL [Accessed: 18.07.2012]. PDF

This Fact Sheet describes: (1.) The processes that occur when chlorine is added to water, and the definitions involved with these processes; (2.) How and why the Safe Water System project recommends testing of free chlorine; (3.) Methods to test free chlorine in the field in developing countries.


Reference icon

TREVETT, A.F.; CARTER, R.C. (2008): Targeting Appropriate Interventions to Minimize Deterioration of Drinking-water Quality in Developing Countries. Dhaka, Bangladesh: International Centre for Diarrhoeal Disease Research. URL [Accessed: 05.04.2012]. PDF

In developing countries, it has been observed that drinking water frequently becomes recontaminated following its collection and during storage in the home. This paper proposes a semi-quantified ‘disease risk index’ (DRI) designed to identify communities or households that are ‘most at risk’ from consuming recontaminated drinking water. A brief review of appropriate physical and educational intervention measures is presented, and their effective use is discussed. It is concluded that incorporating a simple appraisal tool, such as the proposed DRI, into a community water-supply programme would be useful in shaping the overall strategy requiring only a minimum of organisational learning.


Reference icon

WHO (Editor) (1997): Guidelines for Drinking-water Quality. Second Edition, Volume 3. Surveillance and Control of Community Supplies. Geneva: World Health Organization (WHO). URL [Accessed: 04.04.2012]. PDF

This volume of Guidelines for drinking-water quality describes the methods employed in the surveillance of drinking-water quality in the light of the special problems of small-community supplies, particularly those of developing countries, and outlines the strategies necessary to ensure that surveillance is effective. It is also concerned with the linkage between surveillance and remedial action and with the form that remedial action should take.


Reference icon

WHO (Editor) (2006): Guidelines for Drinking-water Quality. FIRST ADDENDUM TO THIRD EDITION. Geneva: World Health Organization (WHO). URL [Accessed: 19.01.2011]. PDF

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.


Reference icon

WHO (Editor); UNICEF (Editor) (2012): Rapid assessment of drinking-water quality. A handbook for implementation. Geneva: World Health Organization. URL [Accessed: 08.11.2012]. PDF

This handbook describes the methods and procedures of the Rapid assessment of drinking-water quality (RADWQ) applied by WHO and UNICEF to explore the quality of drinking-water from "improved" sources in five countries. The handbook is for adoption by any authority or institution that wants to prepare a snapshot of the quality of "improved" sources of drinking-water, as a first step towards strengthening drinking-water quality regulations.


Reference icon

WQHC (Editor) (2012): Safe Water Delivered Safely. Water Quality and Health Council (WQHC). URL [Accessed: 10.04.2012]. PDF

This document will first review the types of water pipelines used throughout the U.S. and Canada, the types of structural problems some of these pipes experience and the costs that are incurred due to these structural problems. Because pipeline structural problems can lead to contamination, this document will also discuss the increased threat of waterborne diseases. Finally, because chlorine chemistry plays a major role in safely delivering water to homes, businesses and schools - through both disinfection and piping material - this paper will show how pipelines made from chlorine-based vinyl plastic are part of the solution to these water-transport challenges.


Reference icon

HAYES, C. (Editor) (2010): Guide for Small Community Water Suppliers and Local Health Officials on Lead in Drinking Water. London: International Water Association (IWA) Publishing. URL [Accessed: 01.11.2013]. PDF

This Guide is an abbreviated compilation of the wide range of scientific, engineering, health and operational issues concerned with the control of lead in drinking water in small water supply systems. It explains why lead in drinking water may still be a threat to public health in small communities. It is aimed at Local Health Officials and the operators of drinking water supply systems that serve small communities. Its objectives are to raise awareness, to provide a basis for assessing the extent of problems, and to identify control options.


Important Weblinks

http://www.mindfully.org/ [Accessed: 10.04.2012]

This short article, based on the Book “Drinking Water Distribution Systems” of National Research Council, describes the permeation and leaching process in piped water distribution systems.