Effective treatment of high phosphorus pharmaceutical wastewater by chemical precipitation

The conditions for the treatment of high phosphorus pharmaceutical wastewater using chemical precipitation were determined to achieve high efficiency on the removal of total phosphorus (TP). The key factors affecting the TP removal efficiencies of four metal salts (FeCl₃, AlCl₃, MgCl₂, and CaCl₂), such as molar ratio, initial wastewater pH, and reaction time, were investigated. The optimal metal mole ratios of FeCl₃, AlCl_3P, MgCl₂, and CaCl₂ for the TP removal were 1.8:1, 1.8:1, 1.6:1, and 1.6:1 in the initial pH range, respectively. The TP removal efficiencies obtained by FeCl₃, AlCl₃, MgCl₂, and CaCl₂ were 99.8 %, 98.3 %, 96.9 %, and 99.2 % at the optimal mole ratio and pH conditions with 30 min reaction time, respectively. FeCl₃ and AlCl₃ had better removal performance on COD, wherein the removal rates of COD by FeCl₃ and AlCl₃ were 38.6 % and 27.6 %, respectively. FeCl₃ and CaCl₂ were selected for the combined process of removing TP and overcoming the aforementioned problem. The final effluent quality was better than the one only used on one of the four metal salts, in which the removal rates of TP and COD were as high as 99.8 % and 46.9 %, respectively. The combined process with FeCl₃ and CaCl₂ was an effective method for the pretreatment of high phosphorus pharmaceutical wastewater to reduce the processing cost and to decrease the chemical oxygen demand (COD) and TP.