This is such a vague question. Are you asking what it is or how to trace the process?
Water treatment<span> is any process that makes </span>water<span> more acceptable for a specific end-use. The end use may be drinking, industrial </span>water<span> supply, irrigation, river flow maintenance, </span>water<span> recreation or many other uses including being safely returned to the environment.</span>
A desert would be a good example because there is no exact source of water there unless you are in a specific one.
Answer:
pollution control in the air
