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Wastewater Treatment
Counting bacteria colonies on filter membrane under a stereo microscope.
Viruses may be present in raw sludge at concentrations as high as 1,000 virus particles per gram of dry matter. Most of the viruses are those that attack the digestive system, i.e., enteric viruses including the hepatitis A virus. In the soil, some viruses can survive for several
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months in the top soil (first 5-15 cm deep) thus posing a health risk to humans and animals. Assessing microbial composition of wastewater Since it is not practical to test for every potentially pathogenic organism in waste-
water, the degree of pollution is determined by use of indicator organisms. Two groups of organisms used as indicators are the total coliforms and fecal coliforms. The fecal coliform group, however, is considered the most significant indicator of fecal contamination. The coliform group of organisms consists primarily of the genera Escherichia, Enterobacter, Citrobacter and Klebsiella. The coliforms are widely distributed in nature, and many live in the gut of humans and warmblooded animals. These organisms are considered opportunistic pathogens because they generally do not cause disease in healthy individuals. A more rigorous test to assess the extent of fecal contamination and potential health risks may involve testing a suite of microbial indicators (e.g., total and fecal coliforms, enterococci, Escherichia coli, coliphage, Clostridium perfringens and human enteric viruses). Clostridium perfringens is a common cause of food poisoning. Collection of samples Sampling is a critical part of sanitary continued overleaf...
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