Size Distribution Study of Refractory Organic Matter in Leachates from Elevated Temperature Landfills (ETLFS)

摘要

In North America, there are a number of landfills that are experiencing elevated temperatures. Gas and waste temperatures are persistently well beyond 55 °C (131 °F) over a substantial area of a cell(s). The underlying cause for the high temperatures recorded at these elevated temperature landfills (ETLFs) is still not established. Some of these elevated temperature landfills (ETLFs) have received industrial wastes that are known to release heat, but others have not and yet there are sites with both circumstances that experienced elevated temperatures in their landfills.;The use of Ultraviolet light (UV254) for disinfection is becoming popular, however the required 60% UV transmittance criteria is not achieved by treatment plants that employ this method in disinfecting wastewater co-treated with leachate from ETLFs. Due to the high concentration of recalcitrant organic matter present in such 'aggressive' leachate, a significant amount of UV light will be blocked by this leachate even if the leachate makes up only a small percentage by volume of the total municipal flow.;There have been a number of studies about combined physical and chemical treatment methods for treating leachates, however none has been directed at the problem of leachates from ETLF sites. This paper is a characterization of the molecular size distribution of contaminants in untreated and biologically treated leachate, comparing the characteristics of leachate obtained from ETLFs with those from landfills with normal observed temperatures. This is achieved using size fractionation by ultrafiltration (UF) and microfiltration (MF) in conjunction with various analyses (COD, TOC, UV254 absorbance and nitrogen species tests). The analyses were performed on untreated and biologically treated landfill leachates from impacted (areas with elevated temperatures) and non-impacted (areas with normal or expected temperatures) cells in ETLF.;The COD to TOC size distribution comparison of the untreated ETLF leachate show that the impacted leachate has more bioavailable organic matter in the form of Volatile Fatty Acids (VFAs) compared to the non-impacted leachate. This indicates a potential for treatment through aerobic biological activity. The results of the organic pollutant (TOC) distribution after biological treatment (Sequential Batch Reactor, SBR) of the leachate samples however showed that biorefractory organic matter below 0.002 microm was dominant after treatment. The size range of these substances should have made them accessible to bacteria for decomposition but their refractory nature is also due to their chemical structure and not only their molecular weight. In addition, the recalcitrant organic substances significantly absorb UV 254 at about the same size range in which reduction in COD and TOC concentrations were low after SBR treatment. The study's findings conclude that the ETLF impacted leachate is leachate at the acid phase of decomposition. This leachate however has high concentrations of COD and solids accumulated over time, which are not in tandem with the typical leachate COD and solids concentration values at a similar phase of anaerobic degradation. Thus, during the anaerobic degradation process at the ETLF landfill site, the impacted leachate is stuck at the acid phase and inhibited from proceeding to complete decomposition.;Ultimately, the most important benefit derived from this study of the size characterization of pollutants is the development of an improved rationale for the selection, design and evaluation of ETLF leachate treatment systems.