Physicochemical and biological treatability study of textile dye wastewater
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The textile industry discharges a highly colored wastewater characterized by high organic levels. Industrial wastewater with these characteristics can be harmful to receiving streams and municipal plants, and must be treated prior to discharge. In this project, a yam dyeing facility was studied that uses biological treatment followed by chemical coagulation to treat their highly colored wastewater prior to discharging to the local river. Occasionally, color, organic, and metal concentrations exceed the effluent discharge limits set by the state. In this research project, many physical, chemical, and biological treatment processes were attempted on the facility's wastewater to determine the most economical and efficient way to treat the wastewater.
Initially, the wastewater was segregated into eight waste streams and characterized. These waste streams included three dye waste streams (acid dye, premetallized dye, and cat-acid dye), three rinse water waste streams (acid rinse water, premetallized rinse water, and cat-acid rinse water), a boiler water waste stream and a combination of dye, rinse, and boiler wastes called the combined waste stream. Chemical coagulation, oxidation, and adsorption were attempted on several of these waste streams with limited success. Ferric chloride and the polymer Color Katch 50 were the most effective chemicals used on dye waste streams, producing color removals greater than 90%.
Aerobic biological treatment was attempted on several waste streams in continuous flow and batch tests. Batch tests indicated that the combined waste stream did not require the addition of supplemental nutrients for biological treatment and that at least a five day hydraulic residence time (HRT) was needed for maximum color and organic removals. Two day HRT, continuous-flow reactors receiving combined wastewater were very unstable and failed to biologically treat the waste. Increasing the residence time to seven days improved biological treatment. Soluble COD removal from the combined wastewater was about 93% and color removal was about 80% in the seven day reactor. A seven day HRT, continuous-flow reactor receiving a combination of rinse waters and boiler water was also successful. Eighty-four percent of the soluble COD and up to 70% of the color was removed from this waste combination. Color Katch 50 was used to remove residual color from the effluent of the seven day HRT reactors. On average, color in the combined effluent was reduced from 1,826 ADMI units to 163 ADMI units, and color in the rinse and boiler water effluent was reduced from 581 ADMI units to 356 ADMI units.
- Masters Theses