Chromium removal from tanning effluent using biomass of Aspergillus oryzae

In tannery industries, Cr+3 is used for tanning animal hides. Three valence chromium reacts in specific conditions with existing organic compounds and manganese ions to change to hexavalent chromium which is considered hazardous for human health. Aspergillus oryzae grew in different dilutions (10-90%) of tanning house effluent (concentration of Cr+3 = 120- 1080 mg/L). The maximum chromium removal rate, (48.2%), was observed at pH = 3.3, Cr+3 concentration = 240 mg/L and size of inoculum = 0.12% (dry weight). Effects of various factors such as pH, temperature, shaking velocity and nutrients were also investigated. At optimum conditions (pH = 5; temperature = 30 degree centigrade, shaking velocity = 150 rpm and nitrogen source of dihydrogen ammonium phosphate concentration = 0.3%), biomass growth and chromium removal rate were found to be 0.45% of dry weight and 99.8%, respectively. Statistical studies on factors such as pH, temperature, shaking velocity, type and concentration of nutrients on the "biomass growth" and "residual chromium", showed that all the factors had significant effects.