A stability study of an advanced co-treatment system for dye wastewater reuse

For dye wastewater reuse, an advanced co-treatment system was designed, using polyvinylidene fluoride (PVDF) membrane and ozone. A small-scale pilot plant was continuously operated for 24 h with three modes: a membrane separation process (mode 1) and combinations of mode 1 and an ozone treatment with air injection (mode 2) or pure oxygen injection (mode 3). In case of disperse dye black, the removal efficiencies of CODcr were found to be 42, 49 and 54% with modes 1, 2 and 3, respectively, suggesting a positive effect of ozone oxidation on organic matter removal whereas T-N and T-P removals were insensitive to ozone treatment, having about 40 and 80%, respectively, regardless of mode types. The color removal efficiency increased from 50 (mode 1) to 89% (mode 3), indicating a great effect of ozone oxidation on color removal. In particular, it was observed that ozone treatment with pure oxygen injection (mode 3) enhanced the color removal by 10%, compared with air injection (mode 2).