Three quarters of the earth's surface is covered by the ocean of water, so water is one of the important external environments for human beings. Similarly, water is also an important part of human internal environment, because water is the medium of human metabolism. The human body needs to constantly absorb water and nutrients from the outside, not only to transport various nutrients to all parts of the body through water, but also to excrete metabolites through water. And the water also contains a variety of trace elements. If the water quality is poor, or it is polluted halfway, the health consequences can be imagined.