Chapter 3: water quality and water resources:
• Diarrheal deaths, most due to waterborne infectious agents,.
• While the widespread use of oral rehyderation thearphy has substantially reduced
the mortality associated with waterborne disease, intensive efforts to provide
improve water and sanitary infrastructure in developing nations have been less
• Growing evidence indicates that updating the means of disposal of human wastes
improves human health to a greater extent than purveying clean water supplies.
• Sources of water:
• Drinking water is obtained primarily from surface water, such as streams, rivers and
lakes or from ground water through artesian or other types of wells.
• Other means of obtaining water include collecting rainwater, desalinating seawater.
• Surface water is in general, more prone to contamination by both microbial
pathogens and chemicals since it directly receives industrial and municipal
wastewater and runoff from the land.
• Ground water usually less contaminated than surface water because the soil through
which it proclates serves as a filter.
• Uses of water:
• Most water is used by toilets, and then cloth washers, showers, faucets, leaks, other
domestic and dishwasher.
• Sources of contamination:
• Contaminants can enter drinking water by a variety of mechanism.
• Many chemicals such as pesticides and fertilizers enter drinking water sources after
being deliberately applied to the land and washing into surface or ground waters.
• Can also enter water through moving through the soil
• Our methods of treating and distributing drinking water lead to some chemical
being present within our drinking water supplies.
• Sources of contaminants that discharge into receiving waters from a pope or other
identifiable device are called point sources.
• Point sources include industrial wastes and sewage treatment plants.
• Sources of contaminations that cannot be defined by discrete pipes or other devices
are called non-point sources.
• Water treatment process:
• The developed world reduced the burden of waterborne disease outbreaks by
implementing a process to treat drinking water in the late nineteenth and early 20
• First water is pumped from its sources. The next step involves adding a chemical
• Water with chemical contamination may need to undergo additional treatment at
this stage, such as activated charcoal or special ion exchange resins.
• Boiling water is the traditional method of water purification, but since it requires
substantial energy production. • Boiling water also involves risk of scalding the lung injury when indoor cooking
fuels are used.
• Both types of water treatment techniques are only effective against microbial
pathogens and do not reduce the concentration of chemical contaminants in the
• Biological threats to water quality:
• World health organization has described five ways water may be associated with
• Waterbrone disease are transmitted by microorganism that survive within water and
are directly ingested.
• Water-washed disease are those exacerbated by inadequate washring of hands or
foods, such as trachoma, other skin and eye infections and many of the fecal-oral
pathogens that cause waterborne disease.
• Water based disease are caused by organisms that spend part of their life cycle as
larval forms within freshwater and come in contact with humans through bating or
ingesting of infested water.
• Water related disease such as dengue fever and malaria are caused by organisms
that breed or otherwise spend part of their life cycle in the water but do not come in
contact with human host through water exposure.
• Water dispersed infections are caused by microorganism, such as legionella, that
proliferate within water supplies and are transmitted to humans by dispersal air and
• Majority of waterborne pathogens infect the gastrointenstinal tract. In which they
enter through contamination by human or animal fecal material.
• Microbial pathogens are usually categorized by human or animal fecal matieral.
• Few microbial pathogesn such as legionally and maycbotermic avium speices, have
the capacity to grow within the pipes of water distribution systems.
• Worldwide, the main bacterial pathogens spread by water are salmnella species,
shigella species, pathogenic E.coli and vibrio cholerae.
• Typhoid fever is characterized by high fevers, abdominal pain and more often
constipation than diarrhea.
• Shigella and other bacteria can cause dystentery, which is charcterizedb y more
sever adbodminal cramping with blood and mucus in the stool.
• Bacteria pathogens are more effectively controlled than viral or protozol pathogens
by existing water treatment processes.
• Boiling water is a traditional method for water purification.
• Boiling water also involves the risk of scalding a