What are some of the feasible methods to treat river water contaminated with industrial effluents?

I'm would like to gain some knowledge about treatment of contaminated river water with industrial effluents. In our Water and Sanitation Project here in Jamaica, Mukuru Slums, Nairobi, Kenya, we have an operational WASH project. However, we have been going through a lot of challenges with regard to accessing clean water regularly. I am wondering if there are feasible methods for treatment of Ngong River that flows near our project area. My idea is to seek ways to transform this River water and make it usable for our WASH Project and for domestic use. Thank you and looking forward to your insights. David.