The factors affecting chromium precipitation in leather tanning industry wastewater

Chromium, the important toxic pollutant in leather tanning wastewaters is c ommonly removed by chemical precipitation. However, there are many factors affecting the efficiency of process. In this paper, chromium precipitation as hydroxide was experimentally evaluated in both synthetic and leather tan ning wastewaters. Results indicated that high chloride content of 6000 mg/l did not affect the process performance. Coagulation using FeCl3 and alumin ium sulfate as well as kaolin proved to be quite useful to provide a clear supernatant. Wastewater components increased the soluble chromium level as compared to synthetic sample due to solubilization possibly by complexation .