Pretreatment of tannery wastewaters by an ion exchange process for Cr(III) removal and recovery

Conventional treatment of tannery wastewaters includes the physico-chemical treatment in order tb precipitate metals (mostly Cr(III). The landfilling disposal of mixed physico-chemical and biological tannery sludges is an economical and environmental problem, due to the saturation of possible sites. A new process, namely, IERECHROM(R) (Ion Exchange REcovery of CHROMium), has been developed for removal, recovery and reuse of Cr(III) ionic complex from segregated tannery wastewaters. The process is based on the use of a weak electrolyte macroporous carboxylate resin, retaining the metal of reference together with other trace metals, including aluminum and iron. A 10 m(3)/d fully automated pilot plant was assembled and a demonstration campaign was carried out at a medium size Italian tannery by using the IERECHROM process; The adoption of the IERECHROM process simplified the tannery wastewater treatment lay-out as the physico-chemical treatment was not necessary. A considerable decrease in the use of chemical compounds, a sludge production reduced by 80% with respect to the traditional treatment, and lower costs for sludge treatment and disposal were demonstrated.