A Novel Approach for Rapid Dewatering of Water-Based Ink Wastewater Sludge under Low Temperature and Its Mechanism

Enhanced dewatering remains a major challenge in sludge disposal. In this paper, a thermal solidification treatment under low temperatures was first and successfully employed to improve the dewaterability of sludge from water-based ink wastewater. A total of 95.1% of dewatering ratio, 36.6% of moisture content, and 91.9% of sludge volume reduction could be acquired at 75 °C and 30 min setting time by the reported approach. The DSC results indicated that a large amount of bound water trapped in sludge could be released into the bulk solution to become free water after thermal solidification treatment. The bound water content of sludge can be reduced from 3.40 to 0.20 g g−1 dry solid. The reported thermal solidification treatment is a thermophysical process that does not involve the solubilization of solid substrates and does not cause an increase in the COD value of dehydrated water. The obtained sludge after cooling was a clot of compacted cake with a uniform coralline-like structure. The softening and shrinking of acrylic resin within the sludge during heating contributed to the formation of compacted cake and thus enhanced the dewaterability. This study offers an economical and efficient treatment of sludge for the water-based ink printing industry.