Question

some deposits were observed in water preserved in aluminium containers after two to three days what could the formation of these deposits​

Answer 1

The deposits found in the container are usually from the water. When the water is stirred, these deposits settle down on the bottom of the container. The deposits are noticeable because they are not soluble in water. In the case of hard water, the deposits are usually the salt deposits that contribute to the hardness of the water.