ORIGINAL PAPER Solidification/stabilization of hazardous waste sludge obtained from a chemical industry Senem Bayar • I ˙ lhan Talinli Received: 20 March 2012 / Accepted: 17 May 2012 / Published online: 9 June 2012 Ó Springer-Verlag 2012 Abstract In this study, treatment sludge obtained from a chemical-metal finishing industry, which contained poten- tially toxic heavy metals and organics, was characterized, and the performance of the solidification/stabilization (S/S) of the sludge was discussed. The hazard characteristics of the waste were determined by means of extraction proce- dure toxicity test and DIN 38414-S4 Test, as defined in both Turkish and USEPA regulations. S/S studies were conducted using Portland cement to solidify the sludge containing high concentrations of total organic carbon, Cr, Cu, Hg, Ni, Pb, and Zn. The waste/binder ratios of 36 sludge specimens were kept between 0/100 and 40/100. The specimens were cured at room temperature for 7, 28, and 90 days. The compressive strengths of the specimens were measured to determine the feasibility of using solid- ified waste sludge as construction materials. The com- pressive strength values indicated that specimens could be potentially used as construction materials. The heavy metal and organic contents of the extracts of each specimen were detected in concentrations which were lower than the standard concentrations in EPTox and DIN 38414-S4 leaching procedures for the most part. Keywords Solidification/stabilization Á Hazardous waste treatment Á Compressive strength Á Portland cement Á Leaching Introduction Solidification/stabilization (S/S) processes have become widely used technologies as the final treatment step for the treatment of industrial hazardous waste before disposal (Cioffi et al. 2002; Poon and Lio 1997). S/S technologies are potentially useful for improving chemical and physical properties of hazardous wastes to an extent that they are suitable for less expensive disposal or utilization with safety environmental impact (Stegemann and Cote 1996). Stabilization refers to reducing the hazardous behavior of a waste by means of chemical reactions, and solidifi- cation refers to generating a monolithic solid of high structural integrity (Coz et al. 2004). When a specific waste is stabilized by means of a specific binding matrix, a study is necessary to assess its potential to be used as building material and therefore, assess the reuse of the waste instead of safe disposal (Cioffi et al. 2002). Different processes exhibit different setting and curing reactions. However, most of the commercial inorganic S/S systems were thor- oughly in connection with the Portland cement technology used in concrete making. S/S processes develop a very wide variety of strength and durability values depending on many factors: waste type, water content, reagent type, reagent addition ratio (mix ratio), curing time, and tem- perature. Many processes can adjust the final strength and durability values by changing reagent mix ratios (Conner and Hoeffner 1998). Although there is no ideal laboratory test to evaluate the stabilization efficiency for every waste, it is possible to select proper tests based on the aim of the stabilization program and chemical composition of the waste (La Grega et al. 1994). Performance of S/S systems is assessed tra- ditionally using three parameters: leaching behavior, per- meability, and structural integrity (Cohen et al. 1997). S. Bayar (&) Department of Environmental Engineering, Gebze Institute of Technology, 41400 Gebze, Kocaelı, Turkey e-mail: bulut@gyte.edu.tr I ˙ . Talinli Department of Environmental Engineering, Istanbul Technical University, 80626 Maslak, Istanbul, Turkey e-mail: italinli@ins.itu.edu.tr 123 Clean Techn Environ Policy (2013) 15:157–165 DOI 10.1007/s10098-012-0494-1