Emissions of organic compounds from landfills

Sammanfattning: The presence of hazardous compounds in waste presents ahazard to the environment both in the short term and the longterm perspective. Landfills containing organic waste canassimilate certain levels of hazardous organic compounds sincethey offer a potential for retention and possibly degradationof organic constituents during events which occur in landfills.From a literature review the transitions of wastes andleachates with time have been compiled.In this thesis, specific organic compounds have beenidentified in leachates from a Swedish municipal landfill. Theresults showed considerable differences in the nature oforganic compounds identified, and the difficulty to determinethe origin of the compounds. It is not possible to analyse morethan a fraction of the organic compounds present in landfills.The organic compounds are primarily present in µg/l levelsin landfill leachates and only in exceptional cases in highconcentrations in the order of mg/l.A conceptual model was proposed including the most importantprocesses, sorption, water transport, transformation andevaporation. With this model, the physical, chemical andbiological characteristics of specific compounds werecorrelated to the emissions. Automatic experimental equipmentwas then developed with which different landfill processescould be examined at the µg/l concentration level. Thelaboratory equipment was used for determining the sorption oforganic compounds to actual waste. The time for reachingsorption equilibrium varied from hours to days, depending onthe hydrophobicities of the compounds. The sorption could bedescribed as linear, at least within limited concentrationintervals. The sorption was also found to be linearlycorrelated with the Kowof the compounds.Further the transport of organic compounds with percolatingwater through a pilot-scale landfill containing 540 m3of waste was examined. It was concluded that thewater was percolating along preferential flow paths through thelandfill, together with fractions of the added compounds.Laboratory experiments indicated that the transport of organiccompounds with mobile particles and colloids was significant.The fate of the organic compounds inside the landfill wastheoretically estimated from literature data concerningsorption, evaporation and transformation. It was concluded thata good correlation existed between the measured emissions andthe theoretically evaluated fate. It is therefore suggestedthat the emissions of organic compounds from landfills can bequalitatively predicted from literature data. Forquantitativepredictions the amount of a compound present in the landfillmust be known.Keywords: organic compounds, municipal landfills,sorption, transport, preferential flow