Toxicity Characteristic Leaching Procedure for Health Assessment of Stabilized Plating Sludge Using Amendments

Background: The occurrence of heavy metals in the environment is of important concern due to their toxicity and health effects on humans, including cancer. Because metals have been extensively used for centuries in commerce, environmental contamination is widespread; moreover, exposure to metals and metal compounds continues to be a significant public health problem. Electroplating sludge contains heavy metals. Solidification/Stabilization can be used to avoid leaching of these metals to the environment. The aim of this study was evaluating the effectiveness of the application of dicalcium phosphate (DCP) and sodium tripolyphosphate (STPP) on Cd, Co, Cu, Ni, Pb and Zn immobilization in dewatered metal plating sludge. Methods: The ratios of STPP and DCP per dry plating sludge were determined to be 0.1%, 0.2% and 0.5% by weight. Metal leaching from the solidified plating wastes was assessed using the toxicity characteristic leaching procedure (TCLP). The results showed that the concentration of metals in untreated sludge were appropriate to classify this sludge as a hazardous waste as described in The Code of Federal Regulations (CFR) 40 CFR 261.24. Results: DCP and STPP lowered the concentration of metal in the effluent. Increasing DCP concentration from 0.1 to 0.5% decreases the contaminant concentration in the effluent. F or Cd, Pb, Cu and Ni increasing the percentage of STPP in the sludge increases the contaminant’s concentration resulting from TCLP extraction. Conclusion: Immobilization of heavy metals was more effective through application of DCP rather than STPP. Moreover, it may minimize the potential risk of groundwater eutrophication connected with the application of highly soluble phosphate like STPP.