One way to minimize or prevent water pollution is to discipline all the people who are using water.
Minimize also the use of pesticides, herbicides and fertilizers. DO NOT  DISPOSE all of these chemicals into the sanitary sewer system because all of these will end at the river.
DO NOT dispose households chemicals down the sink or toilet . AVOID using the toilet as wastebasket, most tissues, wrappers and other paper goods should be put at trash cans not in toiletbowl.
All of these causes water pollution because of being irresponsible.