Mitigation strategies for the removal of rinsate organics and lithium-based dyes from textile effluents

Abstract

Governmental agencies have set regulatory values on the concentration of dye-related color that can be released in textile mill effluents. A proprietary biotic and abiotic technology treatment train was built at a candidate facility in northwestern Georgia to reduce the organic content and dye-related color content in the textile mill’s effluent. Laboratory experimentation began with bench scale 4 L immobilized microbe (IMBR) bioreactor tests to biologically treat primary wastewater streams, namely skein dye and space dye, from this candidate facility. The biological treatment reduced the organic content levels, expressed as chemical oxygen demand (COD), from 3185±30 to 290±20 mg/L (COD reduction rate: 43.21±0.1 mg/L/h) in the skein dyeing effluent and from 5430±30 to 550±120 mg/L (COD reduction rate: 72.8 ± 1.3 mg/L/h) in the space dyeing effluent; however, the biological process did not remove all of the color from the effluent sample. An ozonation unit was added to the biological treatment process to aid in color reduction. The ozonation successfully reduced the residual color in both primary effluent streams. The skein dyeing effluent was reduced from 4.9 to 0.3 mg/L of residual color (color removal rate: 0.069 mg/L/h). The space dyeing effluent was reduced from 16.0 to 1.5 mg/L of residual color (color reduction rate: 0.21 mg/L/h). Both organic content and color removal exhibited >89% reductions. However, to produce water devoid of color from the effluent samples, activated carbon was added and filtered out to further clarify the ozone treated water. The resultant water was of recyclable quality. These laboratory processes were then adapted to create a commercial scale technology treatment train at the candidate facility. The commercial unit, operating at 110 gpm (gallons per minute) with a system hydraulic retention time of 41.6 hours, had reduction levels of >78% for both organic content reduction and color removal. These levels were acceptable treatment levels with the resultant effluent successfully recycled into the dye house processes. Thus, recyclable process water was produced from the effluent waters of the candidate textile mill facility.