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.

The study proved that the RO membrane technique is able to separate chromium efficiently from the pretreated tanning wastewater. It found that the high concentration of NaCl largely affected adversely chromium separation. Inhousekeeping study proved that it is possible to easily reduce NaCl to be lower than 5000 mg/l. Under such conditions, the low-cost RO mem- The authors are indebted to US Egypt Science and Technology Program for financial support of this work. The authors are grateful to Engineer Taha Eid and Engineer Ali Hassan, chairpersons of Radio Tan and Cairo Tanneries for their help during the project period.