The use of alkali to remove Cr from the tanning wastewater is a technology sometimes used in the tanneries. Guoet al. (2006) performed a comparative study of five different alkalis, NaOH, NaHCO3, Na2CO3, MgO, and CaO, where they evaluated the efficiency of Cr removal, the influence of pH,and the volume of sludge generated. All the alkalis used led tochromium removal efficiencies above 99%. However, the use of NaOH resulted in a higher volume of sludge.