Natural attenuation and characterization of contaminants composition in landfill leachate under different disposing ages.
ABSTRACT Chemical Oxygen Demand (COD) composition in landfill leachate would vary as the disposal time extended. Leachates with different ages were collected from Laogang Refuse Landfill of Shanghai, the largest landfill in China with a placement scale of 7600 t refuse per day. To characterize COD composition in leachate, samples were size-fractioned into suspended fractions (>0.45 microm), colloid fraction (0.45 microm<fraction<1 K Da MW) and dissolved fractions (<1 KDa MW) based on the molecular weight distribution. The fractions <0.45 microm (including colloid fraction and dissolved fractions) in leachate were further divided into 6 fractions, i.e. hydrophobic bases (Ho-base), hydrophobic acids (Ho-acid), hydrophobic neutral (Ho-neutral), hydrophilic bases (Hi-base), hydrophilic acids (Hi-acid) and hydrophilic neutral (Hi-neutral). It was found that the ratio of TOC/TC in leachate decreased over time, indicating that the percentage of organic matters in leachate decreased as the disposal time extended. It was also observed that the hydrophobic fraction accounted to about 50% of the total matters presented in the fraction <0.45 microm of all leachate samples. The main components in <0.45 microm fraction were the Ho-acid, Hi-acid and Hi-base fractions. The percentage of Ho-acid in leachate decreased from 60.8% (2 a) to 43.2% (12 a). In addition, leachate with different ages was categorized into 3 phases according to the results of Principle component analysis (PCA). TOC/COD ranges of leachate in periods I, II and III were 40-54.6%, 16.9-41.3% and 10-38.9%, respectively, indicating that the COD contribution of non-carbon reduction substances increased over time in leachate. Hence, the corresponding landfill leachate treatment process should be modified according to the leachate characterization. The results obtained in this study might provide the important information for modeling, design, and operation of landfill leachate treatment systems.
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ABSTRACT: Variation and evolution process of leachate can be applied as a reference for landfill stabilization phase. In this work, leachates with different ages were collected from Laogang Refuse Landfill, and characterized with 14 key parameters. Simultaneously, principal component analysis (PCA) was applied to develop a synthetic parameter-F based on these 14 parameters, and a logarithm equation was simulated for the landfill stabilization process finally. It was predicted that leachates would meet Class I and Class II in standard for pollution control on the landfill site of municipal solid waste (GB 16889-1997) after 32 years and 22 years disposal under the natural attenuation in the humid and warm southern areas of China, respectively. The predication of landfill state would be more accurate and useful according to the synthetic parameter F of leachate from a working landfill.Frontiers of Environmental Science & Engineering. 06/2014; 8(3).
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ABSTRACT: The management of electronic waste (e-waste) is a serious problem worldwide and much of it is landfilled. A survey of four selected landfills in an arid region of South Australia was conducted to determine the proportion of e-waste in municipal waste and the properties of each landfill site. Leachate and groundwater samples were collected upgradient and downgradient of the landfills for analysis of polybrominated diphenyl ethers (PBDEs) and 14 metals and metalloids, including Al, As, Ba, Be, Cd, Co, Cr, Cu, Fe, Ni, Pb, Sb, V and Zn. Our data demonstrate that the selected landfills in South Australia continue to receive municipal waste containing in excess of 6%, or 25,000 tonnes per year, of e-waste. The leachates and groundwater collected from the landfills contained significantly elevated concentrations of Pb with the highest concentration in groundwater of 38 μg/l, almost four times higher than the Australian drinking water guideline of 10 μg/l. The presence of PBDEs was detected in both leachate and groundwater samples. Total PBDEs values of 2.13–59.75 ng/l in leachate samples were 10 times higher than in groundwater samples, which recorded a range of 0.41–6.53 ng/l at all sites. Moreover, the concentrations of metals and metalloids in sampled groundwater contained elevated levels of Al, As, Fe, Ni and Pb that exceeded Australian drinking water guideline values. For these reasons potential leaching of these contaminants is of concern and while difficult to attribute elevated contaminant levels to e-waste, we do not recommend continued disposal of e-waste in old landfills that were not originally designed to contain leachates. The survey also revealed temporal variation in the electrical conductivity and concentrations of As, Cd and Pb present in leachates of landfills in arid Mediterranean climates. These results are consistent with the marked variations in rainfall patterns observed for such climates. The solute concentration (EC and other ions including As, Cd and Pb) declines in the leachates during wet winter months (June to September), in contrast to tropical countries where such changes are observed during wet summer months.Waste Management 11/2014; · 3.16 Impact Factor
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ABSTRACT: Final disposal of Municipal Solid Wastes – MSW in landfills is still well accepted and used for its economic advantages; however, this type of disposal is the responsible of greenhouse gas emission and leachate production. The leachate resulting in landfills comprises a very complex composition of organic, inorganic and heavy metal content, therefore, to determine the strategies to balance the potential toxic effect of this substances in the environment it is necessary an appropriated characterization. The current regulatory approach considers the physic-chemical characterization and the toxicological assessment for this type of liquid wastes, as well. The main objective of this work was to determine the influence of the leachate age over the physic-chemical properties and its toxicity using Daphnia pulex as indicator organism, in acute and static test for 48h. Leachates studied where sampled from different aged landfills: Young leachate (JL) for less than 5 years, Intermediate aged leachate (IL) between 5-10 years and Mature Leachate (ML) for more than 15 years. It was found that physic-chemical parameters such as COD, conductivity and ammonia nitrogen are inversely proportional to the leachate age. The Daphnia pulex toxicity essays showed a less toxicity for the oldest leachate, with 83.1, 47.7 and 27.7 TU (toxic units) of LC50 for the JL, IL and ML respectively.Afinidad -Barcelona- 04/2013; LXX(563):183 - 188. · 0.11 Impact Factor