ABSTRACT



     Title: "Experimental study of minimizing pollution of effluents from the tanning 
industry using wastewater reuse and treatments of membrane and biological processes"
     Abstract
      The present Doctoral Thesis has studied the contamination reduction of 
wastewater in a tannery company. To achieve that, a water characterization of tannery 
wastewaters has been carried out in order to detect which stages of the process produce 
the biggest amount of contamination. After that, there were performed several tests of 
“unhairing” wastewater reuse on the “soaking” phase and direct reuses from “pickling” 
baths, tannery and re-tannery, and greasing  On each one of these actions, there were 
evaluated both the final quality of the effluents and the characteristics of the processed 
leathers after the wastewater reuse.
      For the global wastewaters, optimization of the physical-chemical treatment was 
studied by means of coagulation-flocculation tests (“jar-test”) with different 
concentrations of coagulants and flocculants and also varying the values of PH. After 
the physical-chemical treatment it was evaluated, at a laboratory level, the addition of a 
biological sequential treatment (SBR). To do that, it was studied the influence of the 
hydraulic retention time, the characteristics of the feeding current (homogenization tank 
water or water after the physical-chemical treatment) and the variation of the feeding 
water PH on the treatment performance. It is a biological process very difficult to apply 
due to the high conductivity of the wastewater and the variability of its characteristics. 
Finally, the water coming from the SBR was treated with membranes, comparing the 
performance of nanofiltration membranes with reverse osmosis membranes on 
laboratory plants.
      The results prove that the combination of the wastewaters reuse, the physical-
chemical treatment, the biological sequential reactor treatment and a process of 
membranes, makes possible the reduction of contamination in tannery industries, 
obtaining furthermore, an effluent with enough quality to be reuse (DQO 14mg/l, Ca+2 
14 mg/l, Na+, SO4-2 45 mg/l y Cl- 177mg/l).