Leachate injection using vertical wells in bioreactor landfills

Leachate recirculation or liquid injection in municipal solid waste landfills offers economic and environmental benefits. The key objective of this study was to carry out numerical evaluation of key design variables for leachate recirculation system consisting of vertical wells. In order to achieve the objective, numerical modeling was carried out using the finite-element model HYDRUS-2D. The following design parameters were evaluated by simulating liquid pressure head on the liner and the wetted width of the waste under steady-state flow conditions: (1) hydraulic conductivities of the waste and vertical well backfill; (2) liquid injection rate and dosing frequency; (3) well diameter, screen height and screen depth; and (4) hydraulic conductivity of the leachate collection system, slope of the leachate collection system and spacing of the leachate collection pipes. The key findings of this study are as follows. The well diameter, hydraulic conductivity of the well drainage pack, and screen height and screen depth of the well have very little effect on the wetted width for a given liquid flux. The wetted width and the injection pressure for a given liquid flux decrease with the increase in the hydraulic conductivity of the waste. The pressure head on the liner increases with the decrease in the vertical distance between the bottom of the well screen and the top of leachate collection system. The liquid injection flux increases with the decrease in hydraulic conductivity of the leachate collection system. Unlike sand (k approximately 10(-4)m/s), pea gravel (k approximately 0.01 m/s) resulted in less than 0.3m pressure head on the liner for all simulations carried out in this study.     

Leachate recirculation effects on waste degradation: study on columns

The purpose of this study is to determine the impact of leachate recirculation on the degradation of municipal solid wastes (bioreactor concept). The study was carried out using columns containing approximately 50 kg of waste, in order to follow waste degradation over a limited time. Three types of waste were studied: fresh waste of standard composition, fresh waste of fermentable composition and some 8-yr-old waste extracted from a site in France. Measurement of the global parameters, such as chemical oxygen demand (COD), volatile acidity, alkalinity, leachate conductivity, methane potential of the wastes and biogas production monitoring (volume of CO2 and CH4 produced), were carried out. The quantity of oxydizable matter and biogas production was increased by the leachate recirculation, and the duration of the first degradation phases was reduced in all cases. Chloride, ammonium and organic pollution accumulation was observed according to the duration of recirculation. After 400 days of degradation, waste stabilization seemed to be reached for all of the recirculated columns (COD<300 mg/L O2, and methane potential reached).     

Estimating naphthenic acids concentrations in laboratory-exposed fish and in fish from the wild

Naphthenic acids (NAs) are the most water-soluble organic components found in the Athabasca oil sands in Alberta, Canada, and these acids are released into aqueous tailing waters as a result of bitumen extraction. Although the toxicity of NAs to fish is well known, there has been no method available to estimate NAs concentrations in fish. This paper describes a newly developed analytical method using single ion monitoring gas chromatography-mass spectrometry (GC-MS) to measure NAs in fish, down to concentrations of approximately 0.1mgkg(-1) of fish flesh. This method was used to measure the uptake and depuration of commercial NAs in laboratory experiments. Exposure of rainbow trout (Oncorhynchus mykiss) to 3mg NAsl(-1) for 9d gave a bioconcentration factor of approximately 2 at pH 8.2. Within 1d after the fish were transferred to NAs-free water, about 95% of the NAs were depurated. In addition, the analytical method was used to determine if NAs were present in four species of wild fish - northern pike (Esox lucius), lake whitefish (Coregonus clupeaformis), white sucker (Catostomus commersoni), walleye (Sander vitreus) - collected from near the oil sands. Flesh samples from 23 wild fish were analyzed, and 18 of these had no detectable NAs. Four fish (one of each species) contained NAs at concentrations from 0.2 to 2.8mgkg(-1). The GC-MS results from one wild fish presented a unique problem. However, with additional work it was concluded that the NAs concentration in this fish was <0.1mgkg(-1).     

Mechanical Property Characterization of Plasticized Sugar Beet Pulp and Poly(Lactic Acid) Green Composites Using Acoustic Emission and Confocal Microscopy

Sorbitol and glycerol were used to plasticize sugar beet pulp-poly(lactic acid) green composites. The plasticizer was incorporated into sugar beet pulp (SBP) at 0%, 10%, 20%, 30% and 40% w/w at low temperature and shear and then compounded with poly(lactic acid) (PLA) using twin-screw extrusion and injection molding. The SBP:PLA ratio was maintained at 30:70. As expected, tensile strength decreased by 25% and the elongation increased. Acoustic emission (AE) showed correlated debonding and fracture mechanisms for up to 20% w/w plasticizer and uncorrelated debonding and fracture for 30–40% sorbitol and 30% glycerol content in SBP–PLA composites. All samples had a well dispersed SBP phase with some aggregation in the PLA matrix. However, at 40% glycerol plasticized SBP–PLA composites exhibited unique AE behavior and confocal microscopy revealed the plasticized SBP and PLA formed a co-continuous two phase system.

Therapeutic governance: psycho-social intervention and trauma risk management,.

This paper critically analyses the significance of psycho-social intervention as a new form of international therapeutic governance based on social risk management. First, the paper examines the international psycho-social model and its origins in an Anglo-American therapeutic ethos. Second, the paper argues that psycho-social approaches jeopardise local coping strategies. Third, the paper highlights the potential political, social and psychological consequences of the pathologisation of war-affected societies. Finally the paper concludes that therapeutic governance represents the reduction of politics to administration.     

Molecular response of the sponge Suberites domuncula to bacterial infection

The aim of this study was the documentation of the molecular immune response of Suberites domuncula upon bacterial infection. Additionally, the bacteria that are naturally present in the sponge after prolonged aquarium maintenance were characterized. After 6 months of maintenance of S. domuncula in seawater aquaria, only one bacterial 16S rDNA sequence could be recovered, which belongs to the genus Pseudomonas. Concomitantly, morphologically uniform bacteria were found encapsulated in bacteriocytes. These findings indicate that certain bacteria, possibly of the genus Pseudomonas, are able to persist for long periods in host bacteriocytes. Subsequent to performing a previously established infection assay with S. domuncula, a potentially pathogenic Vibrio sp. was isolated from the tissues. Furthermore, the host tissue disintegrated and asexual propagation bodies (gemmules) were formed. In order to gain insights into the molecular events occurring after bacterial infection, the stress-response kinases, p38 protein kinase and JNK protein kinase, were analyzed. It is demonstrated that these two kinases are activated (phosphorylated) upon incubation of the tissue with the bacterial endotoxin lipopolysaccharide (LPS). Moreover, LPS strongly inhibits protein synthesis. It is concluded that there are many functionally different interactions between S. domuncula and bacteria and that the animal possesses mechanisms to differentiate between bacteria and to respond accordingly.     

Measuring the effectiveness of landscape approaches to conservation and development

Landscape approaches attempt to achieve balance amongst multiple goals over long time periods and to adapt to changing conditions. We review project reports and the literature on integrated landscape approaches, and found a lack of documented studies of their long-term effectiveness. The combination of multiple and potentially changing goals presents problems for the conventional measures of impact. We propose more critical use of theories of change and measures of process and progress to complement the conventional impact assessments. Theories of change make the links between project deliverables, outputs, outcomes, and impacts explicit, and allow a full exploration of the landscape context. Landscape approaches are long-term engagements, but short-term process metrics are needed to confirm that progress is being made in negotiation of goals, meaningful stakeholder engagement, existence of connections to policy processes, and effectiveness of governance. Long-term impact metrics are needed to assess progress on achieving landscapes that deliver multiple societal benefits, including conservation, production, and livelihood benefits. Generic criteria for process are proposed, but impact metrics will be highly situation specific and must be derived from an effective process and a credible theory of change.     

Removal of heavy metal ions from wastewaters using dendrimer-functionalized multi-walled carbon nanotubes

Dendrimer-functionalized multi-walled carbon nanotubes (MWCNT) for heavy metal ion removal from wastewaters were developed. Triazole dendrimers (TD) were built directly onto the carbon nanotube surface by successive click chemistry reactions affording the zero- and first-generation dendrimer-functionalized MWCNT (MWCNT-TD1 and MWCNT-TD2). The Moedritzer-Irani reaction carried out on the amino groups present on the MWCNT-TD2 sample gave the corresponding α-aminophosphonate nanosystem MWCNT-TD2P. Both MWCNT-TD2 and MWCNT-TD2P nanosystems have been characterized by physical, chemical, and morphological analyses. Their chelating abilities towards the toxic metal ions Pb²⁺, Hg²⁺, and Ni²⁺ and the harmless Ca²⁺ ion have been experimentally evaluated in the two different sets of experiments and at the salt concentrations of 1 mg/mL or 1 μg/mL by inductively coupled plasma mass spectrometry (ICP-MS). The results of these studies pointed out the interesting chelating behavior for the phosphonated nanosystem towards the Hg²⁺ ion. The complexation mode of the best chelating system MWCNT-TD2P with mercury was investigated through density functional theory (DFT) calculations, suggesting a chelation mechanism involving the two oxygen atoms of the phosphate group. The synthesized dendrimers, supported on the multi-walled carbon nanotubes, have shown the potential to be used for the selective toxic metal ion removal and recovery.     

Fir decline and mortality in the southern Siberian Mountains

Regional Environmental Change - Increased dieback and mortality of “dark needle conifer” (DNC) stands (composed of fir (Abies sibirica), Siberian pine (Pinus sibirica) and spruce (Picea...