EVALUATION AND TREATMENT OF EFFLUENTS OF THE CONVENCIONAL AND THE ENZYMATIC LEATHER SOAKING PROCESSES, BY PROTEIN PRECIPITATION AND COAGULATION

Abstract

This research consisted of the evaluation and characterization of wastewater generated during the leather soaking process, both in its conventional method and its enzymatic method. The experiments were conducted at an industrial scale at the Helianthus S.A.C. Company in Lima, using 20 cow hides. Likewise, a treatment process was evaluated for these effluents consisting of protein precipitation and was followed by coagulation. Finally, the dry sludge from each treatment method was evaluated separately for its potential use as fertilizer. The process for the chemical precipitation of proteins consisted of applying KOH until reaching pH values of 10, 11 and 12; while the coagulation process consisted of the application of doses of 600, 800 and 1000 mg/L of aluminum sulphate 17%. When using the conventional soaking process wastewater, the proposed treatment system achieved removal efficiencies of 70.3%, 84.9%, 92.4%, 93.4%, 61.8%, 93.9% and 99.6%; when using the enzymatic soaking process wastewater, the system achieved 80.5%, 83.8%, 93.3%, 93.8%, 59.3%; 93.5% and 99.4% removal efficiencies of BOD, COD, TSS, O&F, TKN, S2- and turbidity, respectively. The wastewater from the enzymatic soaking process had a higher level of pollutants than the one from conventional soaking, likely due to a better soaking of the hides with the Tanzyme RD04 enzyme which was used. For the treatment of effluents from the conventional as well as the enzymatic soaking process, the optimum precipitation pH was 12 and the optimum coagulation dose for both effluents was 800 mg/L. The organic content in the sludge was high.