Application 1. Conduct a survey in your locality and collect information on the different measures adopted at the household level for safe drinking water and waste disposal.
Answers
Water has always played a prominent role in human civilisation. Water was, and continues to be, needed for drinking, preparing food, bathing, cleaning, irrigating crops and a variety of other tasks. Having ready access to water, therefore, has always been important. However, the water sources used for supplying water were not always clean. Treating drinking water to improve smell and taste and to remove disease-causing organisms has been necessary throughout human history.
Water must look and taste clean, i.e. have eye appeal and taste appeal, if we are going to want to drink it, and it must also be safe to drink. Water is the breeding ground for an unbelievably large variety of organisms that get into water through a variety of routes. Microbial contamination is the most common and widespread health risk associated with drinking water; therefore treatment of water to eliminate pathogenic microbes is of vital importance. In this study session, you will learn about the public health significance of water treatment, the characteristics of raw (untreated) water that determine the treatment methods, types of household/community–based water treatment and a selection of treatment processes.
Learning Outcomes for Study Session 14
When you have studied this session, you should be able to:
14.1 Define and use correctly all of the key words printed in bold. (SAQs 14.1 and 14.5)
14.2 Explain the purpose of water treatment at household, community and municipality levels. (SAQ 14.2)
14.3 Describe the methods of water treatment at household and community levels. (SAQs 14.3 and 14.4)
14.4 List the stages of large-scale (municipal) water treatment. (SAQ 14.5)
14.1 Waterborne diseases
Diarrhoea, infectious hepatitis, typhoid and paratyphoid enteric fever are all examples of waterborne diseases that are common problems in our country. These are all caused by microbial contamination. Lead poisoning and fluorosis, caused by chemical contamination, are also classified as waterborne diseases.
What distinguishes waterborne diseases from other types of disease associated with water?
Reveal answer
Waterborne diseases can also be classified in a different way as either acute (short-lived) or chronic (long-lasting). Acute health effects occur when the levels of some contaminants in drinking water are high enough to cause acute (immediate) health effects within hours or days of consumption, for example, vomiting. Chronic health effects occur after long-term exposure to a contaminant that may be present only in small amounts. Examples of chronic health effects are liver and kidney damage.
14.1.1 Causes of waterborne disease outbreaks
There are a lot of possible causes for an outbreak of waterborne disease. The use of untreated spring water and surface water, and inadequately or interrupted disinfection of surface water, spring water and well water may all be responsible. These are all causes associated with the source of water but other problems can arise at points in the system after the source. For example, cross-connections of pipework, contamination of water in the household, contamination during the construction of water source protection, contamination of storage facilities including private storage tanks are all contributors. Consumption of water that was not intended for drinking, contaminated bottled water and ingestion of water while swimming are also possible causes.
14.2 Water treatment
The purpose of water treatment is to reduce or remove all contaminants that are present in the water and to improve water quality so that it is completely safe to drink. Water is unlikely to be completely free of contaminants at the original source. The types of water treatment processes depend on the characteristics of the raw water (untreated water direct from its source) and required water quality standards. Suspended solids, bacteria, algae, viruses, fungi, minerals such as iron and manganese, and fertilisers are among the substances that are removed during water treatment. (Suspended solids are tiny particles of solid material that are carried along or suspended in the water.) Effective treatment should ensure the removal of all disease-causing agents and so reduce the possibility of the outbreak of waterborne disease.
Water treatment systems can be categorised as small-scale water treatment, which includes community and household treatment methods, or large-scale water treatment that might be found in towns and cities.
14.3 Small-scale water treatment systems
Household- and community-level treatment systems are the methods most likely to be used in rural areas.