Removal of disperse dyes from textile wastewater using bio-sludge

Granular activated carbon (GAC) did not show any significant adsorption ability on the disperse dyes, while resting (living) bio-sludge of a domestic wastewater treatment plant showed high adsorption abilities on both disperse dyes and organic matter. The dye adsorption ability of bio-sludge increased by approximately 30% through acclimatization with disperse dyes, and it decreased by autoclaving. The deteriorated bio-sludge could be reused after being washed with 0.1 N NaOH solution. Disperse Red 60 was more easily adsorbed onto the bio-sludge than Disperse Blue 60. The Disperse Red 60, COD, and BOD5 adsorption capacities of acclimatized, resting bio-sludge were 40.0 ± 0.1, 450 ± 12, and 300 ± 10 mg/g of bio-sludge, respectively. The GAC–SBR system could be applied to treat textile wastewater (TWW) containing disperse dyes with high dye, BOD5, COD, and TKN removal efficiencies of 93.0 ± 1.1%, 88.0 ± 3.1%, 92.2 ± 2.7% and 51.5 ± 7.0%, respectively without any excess bio-sludge production under an organic loading of 0.18 kg BOD5/m3-d. Furthermore, the removal efficiencies increased with the addition of glucose into the system. The dye, BOD5, COD, and TKN removal efficiencies of the GAC–SBR system with TWW containing 0.89 g/L glucose were 94.6 ± 0.7%, 94.4 ± 0.6%, 94.4 ± 0.8% and 59.3 ± 8.5%, respectively, under an SRT of 67 ± 0.4 days.