Objective: To study the leaching toxicity of the ferric salt and aluminum salt containing arsenic-bearing sludge coming from the high arsenic drinking water treated by coagulation/microfiltration process and its disposal method.
Methods: The Chinese standard method and TCLP method issued by USEPA were used to test the leaching toxicity of arsenic-bearing sludge and its Portland cement solidification tests were conducted. Minor ferric salt containing arsenic-bearing sludge was added into road-application concrete for its utilization.
Results: The arsenic concentrations in TCLP leaching solutions of ferric salt and aluminum sludge were 118 microg/L and 420 microg/L, respectively, which were higher than 9.5 microg/L and 11.8 microg/L of the Chinese standard method. However, all of them were less than identification standard for hazardous wastes of China. When arsenic-bearing sludge was solidified with cement, its leaching toxicity reduced about 90%. The unconfined compression strengths of solidification products were 3.25MPa and 0.76MPa which could meet the requirement for the landfill and sludge reclamation. The compression strengths of road-application concrete were upgraded about 12% when minor parts of ferric salt arsenic-bearing sludge was added.
Conclusion: Ferric salt and aluminum salt arsenic-bearing sludge do not belong to the hazardous waste with leaching toxicity. Cement solidification is an efficient method for the disposal of arsenic-bearing sludge. The mix of arsenic-bearing sludge with road-application concrete could provide a method for the efficient utilization of arsenic-bearing sludge. At the same time, the possible environmental problems should be avoided.