Which of the following is the performance efficiency of slow sand filter?
1. It removes about 98 to 99% bacteria.
2. It removes turbidity to the extent of 50 PPM.
3. It does not remove colour of raw water.
4. It removes about 95% colloidal matter.
1
2 and 3
2
3 and 4
3
1 and 2
4
1 and 4