Question
Microorganisms in sewage.
✓
Answer
- Sewage contains pathogenic bacteria, viruses, fungi, protozoa which cause dysentery, cholera, typhoid, polio and infectious hepatitis, etc. It also contains nematodes and algae.
- Their number and type of microorganisms in sewage depends on the composition and source of sewage.
- Millions of bacteria per ml may be present in raw untreated sewage.
- Bacteria in sewage include coliforms, fecal Streptococci, anaerobic spore forming bacilli and other bacteria found in the intestinal tract of humans.
- The sewage also contains soil bacteria.
- During sewage decomposition, initially aerobic and facultative anaerobic organisms predominate which are followed by strict anaerobic especially methogenic bacteria that produce methane $(CH_4)$ and $CO_2.$
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