Environmental Risk Assessment of Reclaimed Water Purification Using an Agent Prepared from Waste Acid Resulting from Titanium Dioxide Industry

The production of titanium dioxide in China generates substantial waste acid and ferrous sulfate, which are repurposed into polyferric sulfate for industrial wastewater treatment. However, this water purification agent contains heavy metals like Ti, V, Mn, Cr, Co, Cu, Ni, Zn, Ba, and Pb, posing unrecognized environmental risks. This study identified these risks through pollutant screening and the process analysis of a Jiangsu-based titanium dioxide enterprise, evaluating the potential impacts on water quality and worker health. The results show that concentrations of manganese and titanium in the polyferric sulfate reached up to 163 mg/L and 631 mg/L, respectively. Notably, the non-carcinogenic hazard quotients (HQs) for cobalt, vanadium, and manganese were 307, 5.6, and 2.6, all exceeding the safe limit of 1, with cobalt presenting a particularly significant risk due to its low reference dose (RfD) of 0.0003 mg/kg-d. This study concludes that national standards should be revised to include limits for these pollutants to ensure safer practices in industrial wastewater treatment.