Consider the following statements about waste stabilization ponds:

1. The pond has a symbiotic behaviour of waste stabilization through algae on one hand and bacteria on the other.

2. Algae in the pond provide oxygen for degradation through photosynthesis.

3. The detention period for waste stabilization pond is of the order of two to three days.

4. The bacteria, which develop in the pond, are only aerobic bacteria.

Which of these statements are correct?