Particle size distribution in slaughterhouse wastewater before and after coagulation-flocculation

Solid particles were removed from a slaughter house liquid effluent by physicochemical treatment (coagulation-flocculation process) using aluminum sulfate as the coagulant, and activated silica, powdered activated carbon, precipitated calcium carbonate, polyacrylic acid, or anionic polyacrylamide as coagulant aids to improve the settling time. Once the optimal conditions of the coagulation-flocculation process bad been established (speed and time of stirring during flocculation, pH, coagulant and coagulant aid doses), the particle number and size distribution were measured before and after the addition of aluminum sulfate as the coagulant and the different coagulant aids, to determine the efficiency of the coagulation-flocculation process. When aluminum sulfate was used without the coagulant aids, overall efficiency of particle removal was 87%. Use of powdered activated carbon, polyacrylic acid, or anionic polyacrylamide improved removal to values between 92 and 98%.