- 2074 Asoj · 8 marks
Living organisms in water; health effects
Short answer
Water contains bacteria (cholera, typhoid), viruses (hepatitis, polio), protozoa (amoebic dysentery, giardia), helminths (worms), algae (toxins, taste/odour), fungi, and zooplankton (intermediate hosts, mosquito larvae). These cause diseases, taste/odour issues, and filter clogging. Control involves source protection, filtration, and disinfection.
Describe the various types of living organisms present in water. Discuss their effects on human health.
Natural water contains many living organisms; some are harmless, some are harmful and some give problems of taste and odour.
| Organism | Examples | Effects on human health / water supply |
|---|---|---|
| Bacteria | Vibrio cholerae, Salmonella typhi, Shigella, E. coli | Cholera, typhoid, dysentery, diarrhoea |
| Viruses | Hepatitis A and E viruses, polio virus, rotavirus | Jaundice, polio, diarrhoea |
| Protozoa | Entamoeba histolytica, Giardia lamblia, Cryptosporidium | Amoebic dysentery, giardiasis, cryptosporidiosis; cysts resist chlorine |
| Helminths (worms) | Ascaris, hookworm, Schistosoma, guinea worm | Worm infections, bilharzia, dracunculiasis |
| Algae | Blue-green algae (Microcystis), diatoms, green algae | Taste, odour, colour and clogging of filters; some algae produce toxins that affect liver and nerves |
| Fungi and actinomycetes | Moulds, yeasts | Earthy-musty taste and odour |
| Iron and sulphur bacteria | Crenothrix, Beggiatoa | Corrosion, red/black slime, bad smell |
| Zooplankton and small animals | Cyclops, water fleas, rotifers, snails, insect larvae | Intermediate hosts of parasites (Cyclops carries guinea worm); mosquito larvae grow into adults that spread malaria and dengue |
Control
Protect sources from sewage and runoff, control algae by copper sulphate or chlorine, provide filtration and disinfection (chlorination, UV, ozone), and cover storage tanks to prevent mosquito breeding.
✓ Answer checked by Claude Opus 5.5 (high effort)
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