Removal of color from wastewater using various ozonation techniques

Ozone is a strong oxidant that can selectively oxidize the color generating chromophoric parts of the organic compounds in waste waters. In this paper, the removal of color from waste waters produced in municipality, livestock farm, dye and pigment industries are investigated by mechanical diffuser (MD), dissolved ozone floatation (DOF), pressurized ozone oxidation (PO2) and combination of DOF-P02 processes. It is found that decolorization depends on the ozone dosage applied and the apparent concentration of the color imparting compounds in wastewaters. Result shows that 90% color removal efficiency from pigment wastewater is achieved using ozone dose of 108 mg/lscr, 210 mg/lscr and 60 mg/lscr by PO2, mechanical diffuser and combined DOF-PO2 system respectively. Moreover, 10 mg/lscr ozone can reduce the color of municipal waste water from 32 CU to 3 CU using DOF process alone. The order of efficiency among the applied ozonation techniques is found to be DOF-PO2 > PO2> DOF > MD. The more effective DOF-PO2 system is applied in removing color from dye, pigment and high suspended solid containing livestock wastewater and more than 90% color with suspended solids are removed in each case. Thus, ozonation, more particularly DOF-PO2 system is an efficient technology in removing color from various wastewaters.