Journal article

Efficiency and potential environmental impacts of different cleaning agents used on contaminated railway ballast

Railway ballast consists of crushed aggregate and serves as foundation and drainage for railway tracks. Over time, ballast loses its geotechnical properties and cannot be reused within the rail industry but can be sold on to other users to be utilized as a recycled engineering fill. However, it is often contaminated with diesel, grease, lubricating oils, and other deposits from locomotives and carriages. Its reuse generally involves cleaning at a specialist plant. Such contamination may also be removed from geotechnically sound ballast returned to the track where the appearance of dirty ballast is considered unsightly, e.g. in railway stations, and a potential health hazard. Cleaning of the ballast generally involves the use of solvent or surfactant cleaning agents, each with different efficiencies and potential environmental impacts. In this study, the efficiency of three cleaning agents, two terpene-based organic solvents and a surfactant-based system were tested on heavily contaminated ballast using a laboratory-scale cleaning system. The solvents used, both derived from oranges, reduced contamination by 96% or 98%. The surfactant-based cleaning removed 93%. Environmental impacts of residual contamination, solvent or surfactant are discussed and consideration given to the over-all sustainability of the approach including disposal of wastewater.


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