Making dirty water from the Guadalquivir cleaner

In science we´ve been learning about solids and liquids. We´ve also been learning about mixing them and separating them. We made this dirty water cleaner by first removing the biggest particles, like leaves and larger stones with a garden sieve. Next we removed the pebbles with a colander. Then, sand and smaller pebbles with a sieve. We finally removed very fine sand by passing the liquid through filter paper. We decided that it still wasnt safe to drink since it may contain bacteria we couldnt see.