The report describes a bench scale investigation using fly ash adsorption and chemical destabilization techniques to remove color from indigo and sulfur dyeing wastewaters from a denim textile mill. The investigation included a feasibility study and subsequent full scale demonstration flue gas wet scrubbing techniques for neutralizing caustic wastewaters. The fly ash adsorption studies demonstrated that fly ash from a coal-fired boiler can adsorb and subsequently remove color, BOD5, and COD from biologically treated domestic and dyeing process wastewaters. The limited adsorbtion capacity of the fly ash and problems related to fly ash/wastewater contact made full scale application impractical. The chemical destabilization studies included investigation of 11 destabilizing agent combinations, chemical recycle, and various parameters associated with sludge handling and disposal. The studies concluded that calcium hydroxide or aluminum sulfate could successfully remove color and produce a supernatant of suitable quality to recycle. The practicability of using coal-fired boiler flue gases to neutralize caustic wastewaters was demonstrated on full scale. Caustic wastewaters were used with a conventional wet scrubber to successfully neutralize the wastewaters by SO2 and CO2 absorption from the flue gas while simultaneously reducing the particulate emissions.

Prepared by Canton Textile Mills, Inc., Canton, Ga., under grant no. S800852, ROAP no. 21AZT-006, program element no. 1BB036. Tables. Includes appendix. Includes bibliographical references (p. 89-92).