A method for evaluating and verifying biochemical methane potential test completion performed with landfilled municipal solid waste

The biochemical methane potential (BMP) test is significant for the landfill industry as it provides a means to evaluate the gas potential, and therefore potential degradability, of both incoming and in-place municipal solid waste (MSW). However, the BMP test is not standardized making comparison of BMP results across sites problematic. For example, the BMP test duration has historically ranged from 20 days to several months with most current BMP tests lasting 60 days. However, the gas generation data can potentially be modelled for any of those durations to produce a prediction of the ultimate BMP value (BMPULT). Currently, the predicted BMPULT values of 23 long-duration (115-150 days) BMP tests were used to determine the required quantity of data (i.e. number of days) needed to produce an accurate BMPULT prediction. Results showed that no single test duration produced both accurate and efficient results, so a novel performance-based endpoint was proposed. The relative change in predicted BMPULT values with respect to time (dBMPULT/dt) was chosen as a potential performance-based completion metric. Results indicate that once the absolute normalized dBMPULT/dt value is within <2.5, <1.5 and <0.6% day-1 that the predicted BMPULT is within 20, 10 and 5% of the true BMPULT, respectively. Overall, the use of performance-based metrics for determining BMP test completion will allow for the collection of partial data sets, reduced experimental times and verification of results.

Binding of active Ras and its mutants to the Ras binding domain of PI-3-kinase: A quantitative approach to KD measurements

Ras family GTPases (H/K/N-Ras) modulate numerous effectors, including the lipid kinase PI3K (phosphatidylinositol-3-kinase) that generates growth signal lipid PIP3 (phosphatidylinositol-3,4,5-triphosphate). Active GTP-Ras binds PI3K with high affinity, thereby stimulating PIP3 production. We hypothesize the affinity of this binding interaction could be significantly increased or decreased by Ras mutations at PI3K contact positions, with clinical implications since some Ras mutations at PI3K contact positions are disease-linked. To enable tests of this hypothesis, we have developed an approach combining UV spectral deconvolution, HPLC, and microscale thermophoresis to quantify the KD for binding. The approach measures the total Ras concentration, the fraction of Ras in the active state, and the affinity of active Ras binding to its docking site on PI3K Ras binding domain (RBD) in solution. The approach is illustrated by KD measurements for the binding of active H-Ras and representative mutants, each loaded with GTP or GMPPNP, to PI3Kγ RBD. The findings demonstrate that quantitation of the Ras activation state increases the precision of KD measurements, while also revealing that Ras mutations can increase (Q25L), decrease (D38E, Y40C), or have no effect (G13R) on PI3K binding affinity. Significant Ras affinity changes are predicted to alter PI3K regulation and PIP3 growth signals.

Estimating degradation-related settlement in two landfill-reclaimed soils by sand-salt analogues

Landfill reclaimed soil here refers to largely degraded materials excavated from old landfill sites, which after processing can be reinstated as more competent fill, thereby restoring the former landfill space. The success of the process depends on the presence of remaining degradable particles and their influence on settlement. Tests on salt-sand mixtures, from which the salt is removed, have been used to quantify the impact of particle loss on settlement. Where the amount of particle loss is small, say 10% by mass or less, settlements are small and apparently independent of lost particle size. A conceptual model is presented to explain this behaviour in terms of nestling particles and strong force chains. At higher percentages of lost particles, greater rates of settlement together with some sensitivity to particle size were observed. The conceptual model was then applied to two landfill reclaimed soils, the long-term settlements of which were found to be consistent with the conceptual model suggesting that knowledge of particle content and relative size are sufficient to estimate the influence of degradable particles in landfill reclaimed soils.

Indirect measurements of field-scale hydraulic conductivity of waste from two landfill sites

Management and prediction of the movement and distribution of fluids in large landfills is important for various reasons. Bioreactor landfill technology shows promise, but in arid or semi-arid regions, the natural content of landfilled waste may be low, thus requiring addition of significant volumes of water. In more humid locations, landfills can become saturated, flooding gas collection systems and causing sideslope leachate seeps or other undesirable occurrences. This paper compares results from two different approaches to monitoring water in waste. At the Brock West Landfill in eastern Canada, positive pore pressures were measured at various depths in saturated waste. The downward seepage flux through the waste is known, thus the vertical saturated hydraulic conductivity of the waste at this landfill was determined to be 3 × 10(-7)cm/s. By comparison, the Spadina Landfill in western Canada is predominantly unsaturated. The infiltration of moisture into the waste was measured using moisture sensors installed in boreholes which determined arrival time for moisture fronts resulting from major precipitation events as well as longer-term change in moisture content resulting from unsaturated drainage during winter when frozen ground prevented infiltration. The unsaturated hydraulic conductivity calculated from these data ranged from approximately 10(-6)cm/s for the slow winter drainage in the absence of significant recharge to 10(-2)cm/s or higher for shallow waste subject to high infiltration through apparent preferential pathways. These two very different approaches to field-scale measurements of vertical hydraulic conductivity provide insight into the nature of fluid movement in saturated and unsaturated waste masses. It is suggested that the principles of unsaturated seepage apply reasonably well for landfilled waste and that the hydraulic behavior of waste is profoundly influenced by the nature and size of voids and by the degree of saturation prevailing in the landfill.

A design chart for estimation of horizontal displacement in municipal landfills

This paper describes the development of a design chart for the estimation of maximum horizontal displacement within a municipal landfill using the height and the side slope of the landfill. The design chart is based on the results of a finite element parametric study in which the behaviour of the municipal solid waste (MSW) was modeled using a non-linear elastic hyperbolic model. The model input parameters, i.e. non-linear stiffness, shear strength and unit weight of MSW, were obtained from laboratory testing data and an extensive stochastic numerical modelling exercise. Non-linear variations of unit weight as well as Young's modulus of MSW with depth were incorporated in the finite element analyses. The validity of the design chart was assessed using field monitoring results from a large landfill located in Ontario, Canada.

Comparison of slope stability in two Brazilian municipal landfills

The implementation of landfill gas to energy (LFGTE) projects has greatly assisted in reducing the greenhouse gases and air pollutants, leading to an improved local air quality and reduced health risks. The majority of cities in developing countries still dispose of their municipal waste in uncontrolled 'open dumps.' Municipal solid waste landfill construction practices and operating procedures in these countries pose a challenge to implementation of LFGTE projects because of concern about damage to the gas collection infrastructure (horizontal headers and vertical wells) caused by minor, relatively shallow slumps and slides within the waste mass. While major slope failures can and have occurred, such failures in most cases have been shown to involve contributory factors or triggers such as high pore pressures, weak foundation soil or failure along weak geosynthetic interfaces. Many researchers who have studied waste mechanics propose that the shear strength of municipal waste is sufficient such that major deep-seated catastrophic failures under most circumstances require such contributory factors. Obviously, evaluation of such potential major failures requires expert analysis by geotechnical specialists with detailed site-specific information regarding foundation soils, interface shearing resistances and pore pressures both within the waste and in clayey barrier layers or foundation soils. The objective of this paper is to evaluate the potential use of very simple stability analyses which can be used to study the potential for slumps and slides within the waste mass and which may represent a significant constraint on construction and development of the landfill, on reclamation and closure and on the feasibility of a LFGTE project. The stability analyses rely on site-specific but simple estimates of the unit weight of waste and the pore pressure conditions and use "generic" published shear strength envelopes for municipal waste. Application of the slope stability analysis method is presented in a case study of two Brazilian landfill sites; the Cruz das Almas Landfill in Maceio and the Muribeca Landfill in Recife. The Muribeca site has never recorded a slope failure and is much larger and better-maintained when compared to the Maceio site at which numerous minor slumps and slides have been observed. Conventional limit-equilibrium analysis was used to calculate factors of safety for stability of the landfill side slopes. Results indicate that the Muribeca site is more stable with computed factors of safety values in the range 1.6-2.4 compared with computed values ranging from 0.9 to 1.4 for the Maceio site at which slope failures have been known to occur. The results suggest that this approach may be useful as a screening-level tool when considering the feasibility of implementing LFGTE projects.

A new approach to electrical safety testing of electromedical equipment

The "New Approach" to electrical safety testing in Sir Charles Gairdner Hospital (SCGH) is based on the results and experience we have obtained in carrying out such tests for a period of over twenty years. Until recently our testing was carried out according to the annual procedures as described in Standards Australia recommendations. Test protocol changes have, however, now been made since it seemed from our records that we had been carrying out testing to an extent not justified by our test results. The paper describes the safety testing programme now in place at SCGH. This programme has resulted in substantial reduction in the testing time without, in our opinion, compromises in safety. The main elements in electromedical equipment test procedures are:- Acceptance tests In-Service tests Tests after repair We have found that the main consumer of time in electrical safety testing, aside from the test procedure itself, is gaining access to the equipment. This can be particularly difficult in areas where equipment is in constant use, e.g. in CCU, ICU, Renal Dialysis, Operating Theatres, etc. We have developed an earth integrity meter for the purpose of checking medical equipment without the need to disconnect it from the mains supply or from the patient. By means of this device, together with our new testing protocol, access problems have been largely eliminated.

Vector cardiographic assessment of implanted cardiac pacemakers

The design and use of an on-line PDP 11/40 based vector cardiographic pacemaker assessment system is described. The system has been designed for comprehensive, automated testing of either fixed rate or demand implanted cardiac pacemakers. It is accurate and can be operated by a laboratory assistant without special training. Pacemaker parameters extracted are pulse height, width, rate, energy index and the frontal plane vector length and angle at maximum inspiration and during quiet breathing. In addition, a graphical representation of the patient's ECG and the pacemaker pulse is obtained on a computer graphics terminal. Patient data are written to cartridge disk for permanent record following the test. At each subsequent test of the implanted pacemaker, the data on disk are addended with the latest quantitative results. A separate off-line FORTRAN program can interrogate disk files for detailed analysis of patient data and display of parameter trends since implantation.