an average diameter of approximately 80 u03bcm ballast having such a small diameter have a higher specific surface area and generally requires less flocculant polymer to produce ballasted flocs using a ballast having such a small diameter is generally easier to clean than a ballast having a large diameter because the ballast having a small diameter accumulates much less floc and biomass the coagulant added to the wastewater can be either a metallic salt such as iron chloride or aluminum chloride or an organic compound such as polydiallyldimethylammonium polydadmac chloride preferably however the coagulant is ferric chloride fecl 3 which removes residual phosphorus from the wastewater notably since the fecl 3 is added downstream from the biological reactor 1 it does not hinder the growth of the biomass therein the flocculant added to the wastewater can be either an anionic or cationic polymer because the biologically wastewater generally contains less than 2 g l of suspended solids the amount of coagulant and flocculant needed in the ballasted flocculation system is reduced from conventional activated sludge processes the wastewater along with the flocs is directed from the ballasted flocculation system 2 through a baffle 34 to a settling zone 3 where the ballasted flocs settle away from the clarified water the clarified water overflow is collected from the surface of the settling zone 3 through longitudinal chutes 33 which lead to clarified effluent channel 32 the settled ballasted flocs form sludge that is picked up by scraper 31 in the bottom of the settling zone 3 the sludge is then pumped through channel 35 to the.