Application of stability indicators for the assessment of the degradation of residual household waste before landfilling.

In France, domestic waste production is estimated at c 350 kg year-1 per person and landfilling still represents a predominant way of municipal solid waste management, with 39% of waste dumped in 2007. Waste characterization campaigns were conducted at different stages of a mechanical-biological treatment process in order to evaluate its efficiency. Waste samples were sorted by size (>100 mm, <100-20 mm and <20 mm) in order to assess the opportunity for mechanical and aerobic degradation and to reduce the volume of waste landfilled. The monitoring of parameter characteristics of waste stabilization highlighted a decrease in both organic matter and oxidizable organic matter, and an increase in fine particles <20 mm. The respirometric index after 4 days performed on waste samples from the pre-treatment stage showed a decrease in the biological activity compared with the samples taken upstream in the process. The biochemical methane potential of the waste is above the German limit of acceptance in landfills. This intermediate phase of stabilization is confirmed by the results of the leaching tests and hydrophobic fractionation.

Dissolved organic matter: precautions for the study of hydrophilic substances using XAD resins.

This study concerns the possible changes in the repartition and the molecular characteristics of hydrophilic substances (HyS) isolated by XAD resins from the same source of organic matter as a function of the distribution coefficient k' and the DOM concentration. We tested that on two different sources of organic matter (a surface water and a landfill leachate). Breakthrough curves column experiments highlighted a modification of the repartition between hydrophilic and humic substances according to the k' value applied. But, we find that the composition of HyS is significantly modified between k' = 50 and 100. Our observations tend to suggest a higher contribution of humic-like matter (high-molecular weight aromatic compounds) with an increase of the k' value. This results in a shift of fluorescence bands to longer wavelengths and changing patterns of the SEC profiles and molecular fingerprints performed by flash pyrolysis. Our results show that DOM concentration also influences the composition of HyS while little effect is observed on their quantification at k' = 50 or 100.

Combination of biodegradable organic matter quantification and XAD-fractionation as effective working parameter for the study of biodegradability in environmental and anthropic samples.

The present work proposes to couple quantification of biodegradable organic matter (BOM) with XAD-fractionation. Biodegradable dissolved organic carbon (BDOC) and assimilable organic carbon (AOC) analysis were applied to fractions extracted by XAD resin. An examination of mechanisms during consumption of BOM has been carried out, using comparison of biodegradability between the bulk BOM of samples (landfill leachate and surface water) and the sum of BOM contents obtained for the extracted fractions. Results point out that a cometabolism mechanism seems to be involved during the degradation of the surface water fractions. On the other hand, fractions extracted from the leachate seem to be degraded as primary substratum. The more reactive fractions of the leachate (HPO*) and the water (HPI) have been identified as well the less reactive (HPI* and HPO, respectively). The BDOC contents determined for the bulk leachate and surface water are 10+/-2% and 28+/-2%, respectively. The values of AOC are 107+/-18 microg C acetate L(-1) and 163+/-21 microg C acetate L(-1), respectively.

Estimate of the pollution removed by leaching of standard domestic waste: mass assessments carried out in batches and columns.

Batch and column tests allowed estimation of the mobilization of pollution of standard domestic waste in leachate and biogas. Three laboratory tests (biochemical methane potential (BMP), tank leaching test (TLT), and column tests) have been applied to evaluate the emission of pollutants in liquid and/or gas phase from reconstituted municipal solid waste (MSW) on the basis of French waste. In the case of the batch tests (BMP and TLT), BMP tests indicated a maximum organic carbon share produced by waste (biogas potential) equal to 59% of the initial carbon. The maximum quantity of carbon likely to be leached by the waste (TLT) corresponded to 6% of the carbon contained in the waste. On the other hand, during column tests, 3.3% of carbon was leached and 8% of carbon was evacuated in biogas at the end of a 440-day follow-up. It thus appears that the test conditions have a great influence on the remobilization of pollution. In particular it has been proven than the greater the optimization of the liquid/solid ratio, the agitation, the sowing, and the temperature, the greater the pollutant is leached. This study highlights the possible use of batch and column tests to evaluate the pollution risk of a landfill.