Study on reuse of heavy metal rich sludge in ceramic pigment and construction material production

Abstract

In this study, primarily treating waste sludge rich of Cr, Ni, Fe,…generated from electroplating wastewater treatment plant and experimentally methods of utilizing wastes as inorganic pigment in production of bricks were carried out. Economic, technical and environmental efficiency and feasibility, bases to apply to practical conditions were evaluated. The results show that water accounts for about 70% of sludge. Contents of Ni, Cr and Fe are relatively high (20, 4.5 and 2.5%, respectively). The wastes could be used to replace inorganic pigment in brick production after being primarily treated with a simple procedure. The optimal rate of replacing inorganic pigment is about 5% and 20% in case of raw material replacement. The testing results of technical parameters about compressibility, flexibility, size…show all tested products meeting with standard of brick brands commonly used in construction. Environmental safety testing based on heavy metals concentration in rain water soaking tested products (pH value of 5.6-5.9) during 2 to 21 days shows the satisfactory in comparison to the permitted standards (TCVN 5945-2005: Fe< 5, Ni< 0.5, and Cr6+< 0.1mg/l). Cost-benefit calculations of utilizing the wastes reveal that using the wastes to replace inorganic pigment in pavement-tiled brick production gained relatively high economic efficiency and ensure the environmental safety.