Important Points of NCERT - A mere 0.1 per cent impurities | NEET_JEE_NCERT_TRICKS
Important Points of NCERT -
A mere 0.1 per cent impurities make domestic sewage unfit for human use :
Impurities 0.1%
1. Suspended solids, e.g., sand, silt and clay.
2. Colloidal material, e.g., Fecal matter, bacteria, cloth and paper fibres.
3. Dissolved materials, e.g., nutrients (nitrate, ammonia, phosphate, sodium,
calcium).
Daphnia is the indicator of BOD
Water hyacinth (Eichhornia crassipes), the world's most problematic aquatic weed, also called 'Terror of Bengal'.
Minamata disease is cause in humans in Japan by biomagnification of mercury (Hg)
The concentration of DDT is increased at successive trophic levels; say if it starts at 0.003 ppb (ppb = parts per billion) in water, it can ultimately can reach 25 ppm (ppm = part per million) in fish- eating birds, through biomagnification.
