RIWAC - Project for recovery and reuse of industrial waters and trivalent chromium generated by tannery waste processing

Process water containing a high ammonia concentration - chromium (III) present in the residual sludge is usually disposed into landfills. The project managed to obtain recovery of industrial water in a closed loop and the elimination of ammonia related emissions. The process also managed to eliminate fresh water suction from wells and discharges of WWTP (450t/d). Ammonia was absorbed with sulphuric acid and entirely recovered as concentrated ammonium sulphate solution. Also ammonium sulphate was recovered (30-40%) and discharges to the WWTP were eliminated. It can be used among others as nutrient for biological WWTP, in metal production processes, as de-liming agent in tannery industry and in the wood industry. Generally, the economic balance is positive compared to other alternatives: investments costs are by far lower than thermal/catalytic technologies, and ammonium sulphate is recovered and sold.