Which of the following is/are correct?
1
Bulking of sludge does not occur if \(F\over M\) < 0.3/d.
2
The main cause behind the bulking of sludge is the growth of filamentous-shaped bacteria.
3
The detention period of the waste stabilization pond is of the order of two to three days.
4
Oxidation ponds work on the principle of algal symbiosis.