As these substances precipitate from the solution, they carry along microorganisms and adsorbed organics. After settling, the supernatant is collected. Filtration - Next, the water is filtered through sand. This further removes organisms and organics by adsorption. This is an especially important step for removing protozoa that have a cyst phase, e.g. giardia lamblia, because these cysts are often resistant to chlorine.
Some organics are probably still present.