ABSTRACT
The association between water quality and human health has been known for over 150 years. Between 1850 and 1900, studies by Snow, Budd, Escherichia and others led to the development of two important concepts. First, water could transmit microorganisms that caused diseases such as typhoid fever and cholera. Second, coliform bacteria could be used as an indicator of the microbial quality of water.
Since then, several other bacteria, viruses and protozoa have been found to be associated with disease transmission by consumption of contaminated water. Some of these microorganisms that are considered in this chapter include bacteria (Escherichia coli O157:H7), viruses (poliovirus and hepatitis virus) and protozoa (Cryptosporidium and Cyclospora spp.).
Certain diseases, such as typhoid fever and cholera, have been controlled in developed countries but are still problems in some developing countries. Other microbes, such as Escherichia coli O157:H7, Cryptosporidium and Cyclospora spp., continue to be problems for both developed and developing countries. Some of these may cause outbreaks in developed countries but may be endemic in developing countries.
Quantitative models describing the risks associated with pathogens have been developed. These can feed into monitoring programmes to demonstrate risk reduction implemented by the water utility for addressing the potable water supply, irrigation waters and recreational waters, which are also part of the urban cycle. All of the fecal–oral pathogens described herein can be spread through drinking water, irrigation waters (via the food supply) and recreational waters. The water contamination cycle for the urban environment thus goes well beyond the community drinking water. Better assessment of water quality at key locations in the environment and strategic monitoring should be implemented. Findings and recommendations include:
Cholera and typhoid remain the classical water-borne diseases and these are readily monitored for. The health target should be eradication of these diseases. It is clear that any area with cholera and typhoid cases does not have adequate separation of drinking water and sewage and this should be immediately investigated with appropriate monitoring within a risk framework to examine vulnerabilities, so that corrective action can be implemented.
Indicators are useful, although it is now possible for the industry to examine specific water-borne disease pathogens. Risk assessment and probability of infection models can then be, and should be, used by the water industry to address public health based water quality monitoring with established management plans.
There are many stakeholders, in addition to the public, involved in the urban water cycle, including wastewater, agriculture, drinking water and public health. The water industry, in 22particular, needs to form better partnerships with public and environmental health professionals so that water-borne disease and risk assessment methods can be appropriately used and communicated.
