Characterization and resource utilization of dyeing sludge in Taihu Lake Basin, China

Sludge resource recovery has emerged as a promising research field in recent years; however, resource reuse strategies for dyeing sludge remains inadequately explored. This study investigated multiple dyeing wastewater treatment plants across Jiangsu Province, China, and conducted a standardized analysis of the sludge characteristics to explore more effective approaches for its resource utilization. Key sludge properties, including pH, moisture content, organic matter content, and calorific value, were evaluated and statistically analyzed. The results showed that the coefficients of variation for these indicators were 3%, 22%, 29%, and 32%, respectively. Among these parameters, pH remained relatively stable across different wastewater treatment plants (WWTPs), while the other indicators exhibited substantial of dispersion. Correlation analysis revealed significant correlations between organic matter content and moisture content, as well as between organic matter content and calorific value. For heavy metal content in the sludge, sustantial variability was observed across samples, with notable variations in copper (Cu), chromium (Cr), and arsenic (As) levels.These heavy metals are the core limiting factors affecting the resource reuse of the dyeing sludge. Strong positive correlations were observed between lead (Pb) and Cu (Pearson's r = 0.71) and between Cr and As (Pearson's r = 0.61), indicating potential synergistic accumulation characteristics of these heavy metals. Although the sludge generally posed a low potential ecological risk, the elevated pollution levels of Cu and As still constituted a major challenge for its resource recovery, directly restricting the practical application of sludge resource reuse. These findings clarify the fundamental characteristics of dyeing sludge and provide valuable insights for the rational management, risk control, and efficient resource reuse of dyeing sludge.