Physico-chemical characterization and pollutant charge of industrial effluents from tanneries under semi-arid climate

This study was conducted to characterize Marrakech City (Morocco) tanneries effluents. The analysis of 5 different tanneries recipes revealed identical temperatures (25 degrees C), acidic pH ranging from 2.69 to 3.65, electrical conductivity ranging from 40.33 +/- 1.21 to 90.43 +/- 2.40 mS/cm, high chemical oxygen demand (COD: 939.33 +/- 26.46 - 7,739.55 +/- 297.68 mgO(2)/L), biological oxygen demand (BOD: 24-42 mgO(2)/L). In addition, there were high quantities of total suspended solids of about 6,400 +/- 100 - 15,700 +/- 200 mg/L, total dissolved solids (TDS: 22,566.67 +/- 57.74 - 50,900 +/- 100 mg/L), total solids (TS: 28,966.67 +/- 57.74 - 66,600 +/- 264.58 mg/L), sulfate (SO42-: 1,021.43 +/- 61.86 - 2,9 50 +/- 35.71 mg/L). High concentrations of total chromium ranging from 200 to 500 mg/L and Cr6+ from 117.22 +/- 20.19 to 393.37 +/- 42.74 mg/L were recorded. Different size and shape of effluents particles and filaments influence the sedimentation speed and scour velocity, as well as the pollutants adsorption. These results indicate that tanneries effluents are polluted, and the physico-chemical characteristics vary from one to another one. This approach could be useful as a decision-making tool for the implementation of a depollution process adapted to the local socio-economic context.