Out of the below given methods which of these requires a grit removal prior to it?

What is the intermediate zone composed of in aerobic-anaerobic ponds?

What is the amount of solids released into wastewater by human beings?

Which is usually prior to reverse osmosis?

How are colour and odour removed?

Which type of reactor is used for stripping off gases from water?

Which type of reactor is not subjected to back mixing?

How does the chemical sludge appear?