Aqua Nova- river water filter

I know I want my project to be centred around wildlife preservation as it is something I am very passionate about, which lead me to the idea of creating a water filter for my local creek which is home to the endangered species the platypus. My plan is to foster a safe environment for local species by designing and implementing a structure to filter out microplastics and harmful oils, specifically targeting pollutants affecting platypus. I would love some feedback from professionals who know anything about engineering a water filter or suggestions for sustainable materials I could incorporate.