What systems can purify the water in rivers?

Question

I am interested what kind cheap systems exist for purifying the river water from stock breeding pollution.

Thanks in advance for the answers and please consider them as doing your favour to river spirits.

Answer 1

To purify the water first the sedimentation and decantation is done to remove the heavy and solid material parts.

Then alum is added to sediment the smaller solid parts. After then clorine is added to remove impurities. At last it is stored in tanks. This water can be used for fulfiling our needs.

Answer 2

Filtration systems

Answer 3

The same systems that purify water from other sources. First, the big pieces (e.g. branches) are screened out. Alum is added to coagulate smaller particles and they and grit are allowed to settle out. Floating material may be skimmed. Water is usually treated with chlorine or a similar compound; ozone may also be used. Most important, before the water goes out into the mains, it is thoroughly tested. It may have been tested along the way, as well.