Solidification/stabilization of landfill leachate concentrate using different aggregate materials Selda Yigit Hunce a , Deniz Akgul a , Goksel Demir b , Bulent Mertoglu c,⇑ a Department of Environmental Engineering, Marmara University, 34722 Goztepe, Istanbul, Turkey b Department of Environmental Engineering, Bahcesehir University, 34353 Besiktas, Istanbul, Turkey c Department of Bioengineering, Marmara University, 34722 Goztepe, Istanbul, Turkey article info Article history: Received 4 December 2011 Accepted 10 March 2012 Available online 11 April 2012 Keywords: Leachate Reverse osmosis Concentrate Solidification/stabilization Zeolite abstract The application of reverse osmosis for the treatment of landfill leachate is becoming widespread in Tur- key as well as in Europe. A major drawback of this process is the production of concentrate, which could be as much as 30% of the feed stream, and high concentrations of salts and contaminants. The reverse osmosis concentrate is disposed of by using several methods including re-infiltration, drying, incineration and solidification/stabilization. In this study, solidification/stabilization (S/S) technology was studied for the treatment of reverse osmosis concentrate produced from landfill leachate. In order to benefit from its capability to absorb heavy metals, ammonia and some other pollutants, zeolite and different aggregate materials were used in solidification experiments. Main pollutants in the leachate concentrate, TOC, DOC, TDS and ammonia were successfully solidified and approximately 1% of TOC, DOC, TDS and ammo- nia remained in the eluate water. The results indicated that the landfill disposal limits could be attained by solidification/stabilization process. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Solid waste management by landfilling is a widely used method in Turkey. It is the most economical way of disposing municipal so- lid wastes among other alternatives (Lema et al., 1998; Tchobanog- lous et al., 1993). The leachate is generated by the landfilling must be treated before disposal to the receiving environment. All over the world, the leachate formed in landfilling or wild dumping areas cause serious environmental problems. Landfill leachate is waste- water heavily loaded with various types of organic and inorganic contaminants and presents a major risk to natural water resources (Christensen et al., 1992; Li et al., 2009). Among the new processes for leachate treatment, reverse osmosis (RO) generates a high effluent quality and achieves contaminant removal rates better than 99%. Renou et al. (2008) reported that the use of membrane technologies in leachate treatment plants has shown to be an indispensable means of achieving purification. This technology can be used either as a main step in the landfill leachate treatment plant or as the single post-treatment step. The major drawbacks of the application of RO to landfill leach- ate treatment are membrane fouling and the generations of large volumes of concentrate. Membrane fouling requires extensive pre- treatment or chemical cleaning of the membranes and results in a short lifetime of the membranes and decreases process productiv- ity (Renou et al., 2008). All of these consequences cause high oper- ational costs in reverse osmosis operation. The treatment or disposal of concentrate that is produced by reverse osmosis system is the most troublesome issue that must be taken into consider- ation. In general the concentrate is re-infiltrated into the landfill body, sent to a sewage treatment works, thermally incinerated or dried. van der Bruggen et al. (2003) classified the methods used for concentrate processing into the following categories: reuse, fur- ther treatment by removal of contaminants, incineration, direct or indirect discharge in surface water, direct or indirect discharge in groundwater and landfilling. Alternatively Peters (1998) suggested best technology available for concentrate handling are: the trans- port of the concentrate to an incineration plant; solidification of the concentrate with different materials, like fly ash or sludge from waste water treatment plants; and controlled reinjection of the concentrate into changing areas of the landfill body in order to im- prove the biochemical degradation process and accelerate the immobilization of the organic matter. Concentrate return to the landfill site is the most commonly used method for the disposal of reverse osmosis concentrate in landfills. The effects of the recir- culation of concentrate to the landfill body were evaluated in de- tailed by Robinson (2005) in Wischhafen landfill site. According to the author, the return of concentrate to the landfill has an imme- diate effect on the landfill leachate because it causes an increase in COD and ammonia concentration levels and a sharp increase in leachate conductivity. This situation directly affects the perfor- 0956-053X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.wasman.2012.03.010 ⇑ Corresponding author. Tel.: +90 216 3480292; fax: +90 216 3480293. E-mail addresses: bmertoglu@yahoo.com, bulent.mertoglu@marmara.edu.tr (B. Mertoglu). Waste Management 32 (2012) 1394–1400 Contents lists available at SciVerse ScienceDirect Waste Management journal homepage: www.elsevier.com/locate/wasman