RO membrane removal of unreacted chromium from spent tanning effluent. A pilot-scale study, part 2

In chromium tanning. process, about 20-40% of applied chromium is usually discharged into sewerage system causing serious environmental impact. The spent chromium effluents collected from two local. small-size tanneries indicated that chromium concentration ranged from 1300-2500 mg Cr6+/l, while NaCl concentration varies from 40000 to 50000 mg/l. The study of chromium removal efficiency by using of a pilot-scale setup of 7 and 16 bar RO membrane units at different working pressures and under variable salt concentrations were carried out to remove the hazardous chromium from the spent tanning effluent and recover it for further recycling. The study proved that the membrane technique is able to separate chromium efficiently from the pretreated tanning wastewater. The low-cost RO membrane units, i.e. the medium and low pressure, could be used economically for separation and recovery of chromium from wastewater of small-size tanning shops.