एक प्रदूषित जलधारा की सामान्य संतुलित स्थिति को किस प्रक्रिया द्वारा पुनर्स्थापित किया जाता है?

Turbidity in water is measured on which standard scale?

Mudball formation in rapid sand filters is the result of:

In a water sample, if 2 mg of platinum cobalt salt is dissolved in 1 litre of distilled water, then the colour produced is equal to: