Studies of the Composition of Distillates from Leachate by Gas Chromatography/Mass Spectrometry Coupled to Solid-Phase Microextraction

Every day municipal solid waste landfills produce huge amounts of a liquid waste, called leachate, generated mainly by water washing away of the solid waste. Leachate is substantially water containing several organic and inorganic pollutants, usually at trace levels, and must be collected and treated for the mantainance of the landfill. We have studied, on a laboratory scale, an evaporation process for concentration of the leachate, capable of providing a distillate suitable for disposal into surface waters. The distillate was checked for the usual pollution parameters, of which chemical oxygen demand (COD) was the main one. Analysis by gas chromatography/mass spectrometry (GC/MS) was used to identify the organic pollutants, and so to define if toxic substances were present. Solid phase microextraction (SPME) was used to extract the organics from water, by both headspace and immersion methods. We examined the distillates obtained from untreated leachate and also after acidification to pH 4 and basification to pH 10. It was possible to identify several compounds such as phthalates, linear and cyclic unsaturated alcohols, alkylphenols, carbonyl polycyclic compounds, etc. Such compounds were also present in the starting leachate. When the evaporation process was applied to acidified leachate, the composition of the distillate was very similar except for the presence of some aliphatic carboxylic acids not present in the other headspace products, and which could account for the higher COD values of the distillates from acidified leachate.