In order to provide water of a suitable quality, standards have to be set that define the tolerable level for any contaminants that may be in the water supply. Consider the differences in these three approaches to standard-setting.
1 No acceptable risk: no potentially disease-causing agent should be present in the water.
2 No excess risk: there should be no excess hazard from a contaminant. The dose response relationship is important here. A substance is not a contaminant if we cannot detect an effect. To be on the safe side, the standard will apply a level of the contaminant at a specified fraction below that of a detectable effect. For example, if it is known that 50 organisms/100 cm3 will make 5 per cent of the population sick, then we will settle for 5 organisms/100 cm3 and so there is still a finite risk.
3 Economic risk: the best available water, subject to economic constraints and other alternative uses of the money.
102 Environment, Health and Sustainable Development
Individuals and agencies involved in standard-setting for water quality will take these factors into account when they issue guidelines.
The rest of the chapter is taken up by an activity that looks at some of the issues surrounding quality and standards for water.
Activity 7.3
This activity explores implications of adopting a cost–benefit perspective on standards, as opposed to an absolutist approach of ‘safe’ or ‘unsafe’ quality. This raises the potentially controversial notion of differing standards for differing costs or popula- tions, and ‘the dollar value of a human life’. The activity will consider different strategies for water pollution management: treatment at pollutant source vs treatment before ingestion.
A water engineer has been asked to select the best options for establishing a rural water supply for a community of 200 people. She has visited the area and after some research is considering using an underground stream that emerges from a nearby hillside as the best source for the water. She is aware that groundwater is usually clean and safe. There is an alternative source available; a large river that also runs close to the village.
She takes some water samples from the underground stream and the large river and sends them to the ‘Institut Pasteur’ for bacteriological analysis. When the results come back, she presents them in combination with her estimates of the possible quantity of water each source can supply.
After studying the results (Table 7.8), the water engineer is initially considering two options for the supply of safe water to the village; these are set out below.
Option 1: Underground stream
Install a small treatment works which can eliminate all bacteria if properly maintained.
Cost: Installation $20(US)/person then $5/person/year cost of chemicals.
Option 2: Large river
Install sedimentation and filtration facilities before chlorination. This is required because occasionally the water is very turbid (muddy) although most of the time it is remarkably clear. Cost: Installation $200(US)/person then $10/person/year cost of chemicals.
Table 7.8 Water source, bacteria count and available water Water source Bacteria count
(E. coli/100 cm3)
Institut Pasteur verdict Available water (litres per person per day) Underground
stream
20 Suspected as a
contamination source 20
River Styx 1000 Not fit for drinking 200
Water and sanitation 103
The engineer then receives a visit from a local environmentalist who points out that, in addition to pathogenic bacteria, there have been long-standing concerns about upstream pesticide use which may be contaminating the river water. The engineer checks the chemical content of the water for obvious contaminants, and finds 3 µg of DDT (p,p-dichloro-diphenyl-trichloro-ethane) per litre of water, which lies above the recommended water quality guidelines of WHO, which are 2 µg/litre. The engineer is fortunate in that she will be able to remove the DDT from the water for the extra cost of only $20(US)/head.
1 What issues should the engineer consider in order to choose the best option?
2 Should she take the option of removing the DDT from the river water?
3 What other policy options might the state or the pollution control authorities wish to consider?
Feedback
1 The first issue to consider is: What is the supply for the community now and what will it require in the future? You will recall that 50 litres per person per day is the minimum necessary water requirement. The problem of using the underground stream, while it has clean water, is that it may not supply a large enough quantity. One possibility may be to use it as the source of drinking water and use the river water for washing and other uses.
The second issue to consider is: Are there any water-related diseases causing a problem in the village already and how can they be best prevented? It may be a sanita- tion issue – would improved hygiene behaviour be the solution? What are the priorities for those in the village? Will the new water be of better quality than the old water?
The third issue to consider is: What can the community afford to pay and where will the funds come from? How will the supply be maintained and who will pay for it?
2 It will depend partially on how much money is available and whether it is essential to use this water source or whether there are alternate sources. She might need to consider what the DDT standard for her country is.
3 The village will need to consider where the DDT is coming from and how they can control the levels. Is it possible to fine or penalize those who are allowing the DDT to enter the water supply? Are there regulations already and how can limits be enforced?
Summary
Water is a basic human need. The availability of clean water and adequate sanita- tion facilities varies throughout the world, but it is almost always the poorest communities who are most vulnerable to water-related illness as the technological, financial, or hygiene educational infrastructure may be inadequate. In high income countries water-borne diseases are becoming rarer; with increasing industrialization; chemical water pollution is the main concern. In low and middle income countries by contrast, water-related illnesses are the greater source of ill health and death, although the adverse effects of unregulated industrialization are increasingly taking a toll here as well.
104 Environment, Health and Sustainable Development
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Further reading
UN-Habitat (2003) Water and Sanitation in the World’s Cities: Local Action for Global Goals.
London: Earthscan Publications.
Water Aid: http://www.wateraid.org.uk/
World Resources Institute (1998) World Development Report 1998/9. Washington, DC: Oxford University Press.