FYI a flocculant can be used to settle out really dirty water, it needs to be mixed well to work correctly. Flocculants include ferric and alum. Bleach is typically used as a disinfectant to reduce bacteria and viruses. Oocysts are not destroyed by chlorine and have to be filtered out. Most surface water treatment plants use sand filters. Granulated carbon filters are increasingly common to remove trace chemical contaminants, but these will also adsorb chlorine, advise disinfectant after the filter step.