Optimized Coagulation on a Municipal Wastewater Treatment:Competitive and Synergetic Effect Among Different Pollutants

Iron(II) shows an increasingly attractive option among the main metal salts available for phosphorous removal by chemical precipitation. But other anions in the changing wastewater may compete with phosphorous for iron(II) also. Meanwhile, in the absence of oxygen, the iron(II) will not be oxidized and produce a very fine precipitate with phosphorous which is difficult to settle down easily. A case study towards an optimized coagulation system in a municipal WWT plant was therefore carried out to illustrate the competitive and synergetic effect during iron(II) coagulation. The results showed that FeSO(4) can effectively reduce the dissolved total phosphorus (DTP) and sulfide (S(2-)), but total phosphorus (TP) is not reduced. Alum and polyaluminum chloride (PACI) could act as the coagulant aid to develop an effective coagulation process with the emphasis of phosphorus removal from wastewater.