COAGULATION-FLOCULATION PROCESS IMPROVEME NT BY MEANS OF COAGULANT AIDS ADDITION - APPLICATION TO SLAUGHTERHOUSE EFFLUENTS

The physical-chemical coagulation-flocculation treatment has been appl ied to a slaughterhouse wastewater. The following products were chosen as coagulants: Fe-2(SO4)(3) and Al-2(SO4)(3).18 H2O. In order to impr ove the sedimentation rate, the following coagulant aids were employed : activated silica, powder activated charcoal and calcium carbonate pr ecipitate. In the flocculation phase, the conditions of agitation spee d and time (low agitation), pH and coagulant and coagulant aid doses w ere optimum; it was initially established the coagulation rate and tim e (quick agitation) according to the actual literature about the treat ment of this type of waters. it has been also necessary to select a se dimentation time for the optimization of the different variables that take part in the process. For the control of such a process, there wer e determined the values of DQO, DBO5 and SST at the beginning and at t he end of each test. It has been prepared a study about the influence of the sedimentation time in the height of the caracterization area.ss It has been found that the addition of coagulant aids does not really improve the removal yields of organic matter and suspensions solids. Nevertheless, it is observed a remarkable decrease of sedimentation ti mes.