Consider the folloiwng statements about waste stabilization ponds:

1.   The pond has a symbiotic behiaviour of waste stabilization through algae

2.   The oxygen in ponds is provided by algae 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 aerobic becteria.

Which of these statements are correct?