Can i get examples on what kind of water polution are people doing?
I'll start with the most direct kind of water pollution: trash.
I live on the coast, so all wrappers, cigarette butts, and other kinds of trash usually end up in the ocean, which is pretty bad. This has had bad effects on ocean water quality, which anyone who goes to the beach doesn't like.
I won't spend too much time on this one, but if sewage makes its way into a water source... water pollution. The U.S. doesn't usually have too many issues with this, but countries like Brazil often do. Rio de Janeiro soaks up all the sewage and waste from the city, and needless to say, it wouldn't be fun to swim in.
Agriculture is a huge source of water pollution:
Many farmers will use synthetic nitrogen-based fertilizer for their crops to assist growth. The problem is when it rains and the fertilizer drains out into a river or ocean. Nitrogen is prime food for algae, so when there's a whole bunch of nitrogen in a water source, you get what's called an algal bloom. Then, once the algae run out of their food, they all die, and get decomposed by an aerobic bacteria, which basically consumes all the oxygen in the water. This creates dead zones.
Mining can also cause water pollution. In particular mountaintop removal. The process is exactly what it sounds like. People blow off the tops of mountains to get ores inside (used a lot in Appalachia in the U.S.). The companies usually dump all the rock and rubble, and later all the chemicals they used to process and mine the resources into a river valley. Often the chemicals drain into the groundwater, contaminating it, and the sediment is also bad for water quality. Mercury, lead, cadmium, chromium, and a host of other toxic heavy metals often find their way into rivers or groundwater.
Gas emissions from cars can also end up as water pollution because the carbon dioxide can end up in the water and actually cause the water to acidify slightly. If this happens too much, the water can be toxic to aquatic life and bad to drink for us.