PATHOGENS
Coliform
bacteria are a commonly used bacterial indicator of water pollution, although
not an actual cause of disease. Other microorganisms sometimes found in surface
waters which have caused human health problems include: Burkholderia
pseudomallei ,Cryptosporidium parvum ,Giardia lamblia ,Salmonella ,Novovirus
and other viruses Parasitic worms (helminths).
High
levels of pathogens may result from inadequately treated sewage discharges. This
can be caused by a sewage plant designed with less than secondary treatment (more
typical in less-developed countries). In developed countries, older cities with
aging infrastructure may have leaky sewage collection systems (pipes, pumps,
valves), which can cause sanitary sewer overflows. Some cities also have combined
sewers, which may discharge untreated sewage during rain storms.
Muddy
river polluted by sediment. Pathogen discharges may also be caused by poorly
managed livestock operations.
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