P. Lakshmikanthan

Estimation of the components of municipal solid waste settlement.

Estimation of the municipal solid waste settlements and the contribution of each of the components are essential in the estimation of the volume of the waste that can be accommodated in a landfill and increase the post-usage of the landfill. This article describes an experimental methodology for estimating and separating primary settlement, settlement owing to creep and biodegradation-induced settlement. The primary settlement and secondary settlement have been estimated and separated based on 100% pore pressure dissipation time and the coefficient of consolidation. Mechanical creep and biodegradation settlements were estimated and separated based on the observed time required for landfill gas production. The results of a series of laboratory triaxial tests, creep tests and anaerobic reactor cell setups were conducted to describe the components of settlement. All the tests were conducted on municipal solid waste (compost reject) samples. It was observed that biodegradation accounted to more than 40% of the total settlement, whereas mechanical creep contributed more than 20% towards the total settlement. The essential model parameters, such as the compression ratio (Cc’), rate of mechanical creep (c), coefficient of mechanical creep (b), rate of biodegradation (d) and the total strain owing to biodegradation (EDG), are useful parameters in the estimation of total settlements as well as components of settlement in landfill.

Shear strength characteristics of mechanically biologically treated municipal solid waste (MBT-MSW) from Bangalore

Strength and stiffness properties of municipal solid waste (MSW) are important in landfill design. This paper presents the results of comprehensive testing of shear strength properties of mechanically biologically treated municipal solid waste (MBT-MSW) in laboratory. Changes in shear strength of MSW as a function of unit weight and particle size were investigated by performing laboratory studies on the MSW collected from Mavallipura landfill site in Bangalore. Direct shear tests, small scale and large scale consolidated undrained and drained triaxial tests were conducted on reconstituted compost reject MSW samples. The triaxial test results showed that the MSW samples exhibited a strain-hardening behaviour and the strength of MSW increased with increase in unit weight. Consolidated drained tests showed that the mobilized shear strength of the MSW increased by 40% for a unit weight increase from 7.3kN/m(3) to 10.3kN/m(3) at 20% strain levels. The mobilized cohesion and friction angle ranged from 5 to 9kPa and 8° to 33° corresponding to a strain level of 20%. The consolidated undrained tests exhibited reduced friction angle values compared to the consolidated drained tests. The friction angle increased with increase in the unit weight from 8° to 55° in the consolidated undrained tests. Minor variations were found in the cohesion values. Relationships for strength and stiffness of MSW in terms of strength and stiffness ratios are developed and discussed. The stiffness ratio and the strength ratio of MSW were found to be 10 and 0.43.

Seismic characterization and dynamic site response of a municipal solid waste landfill in Bangalore, India

Seismic design of landfills requires an understanding of the dynamic properties of municipal solid waste (MSW) and the dynamic site response of landfill waste during seismic events. The dynamic response of the Mavallipura landfill situated in Bangalore, India, is investigated using field measurements, laboratory studies and recorded ground motions from the intraplate region. The dynamic shear modulus values for the MSW were established on the basis of field measurements of shear wave velocities. Cyclic triaxial testing was performed on reconstituted MSW samples and the shear modulus reduction and damping characteristics of MSW were studied. Ten ground motions were selected based on regional seismicity and site response parameters have been obtained considering one-dimensional non-linear analysis in the DEEPSOIL program. The surface spectral response varied from 0.6 to 2 g and persisted only for a period of 1 s for most of the ground motions. The maximum peak ground acceleration (PGA) obtained was 0.5 g and the minimum and maximum amplifications are 1.35 and 4.05. Amplification of the base acceleration was observed at the top surface of the landfill underlined by a composite soil layer and bedrock for all ground motions. Dynamic seismic properties with amplification and site response parameters for MSW landfill in Bangalore, India, are presented in this paper. This study shows that MSW has less shear stiffness and more amplification due to loose filling and damping, which need to be accounted for seismic design of MSW landfills in India.

Evaluation of Bioreactor Landfill as Sustainable Land Disposal Method

Sustainable municipal solid waste management has become a challenge to the engineers in the present world. Good pretreatment methods coupled with landfilling are looked as sustainable means of disposal of municipal solid waste. Bioreactor landfill is one such sustainable option. In the present study two landfill simulators (dry and leachate recirculation) were used to investigate the effect of leachate recirculation on the stabilisation process of mechanically biologically treated (MBT) municipal solid waste (MSW). The simulator with a leachate recirculation had a higher degree of waste stabilisation towards the end of the experiment due to higher moisture content and micro-organisms. The results observed at the end of 380 days prevail that the process combination of above operational parameters adopted in bioreactor was a more efficient approach for stabilisation of MSW. After 1 year of operation, the residues of the simulators were analysed, and it was found that the settlement and gas production were greater in leachate recirculation simulator than the dry simulator. The carbon content reduced in the bioreactor simulator by more than 60 % compared to the dry simulator. It was also observed that the biodegradation time for MBT-MSW was reduced in bioreactor simulator compared to maximum values presented in the literature.

Assessment of Landfill Sustainability

Assessing landfills in terms of sustainability is a difficult task and needs to be addressed comprehensively. In this paper, we present an initial operationalisation of this approach for a pragmatic legal landfill assessment and its application to assess two prototypic Swiss landfills as part of a pilot study. Thereby, the six generic criteria of SPA are specified using 18 functional key variables (FKVs), such as ‘control of pollutant release’ or ‘resilience to intended human impacts’. The first results from the pilot study indicate that SPA and its generic criteria provide a purposeful guiding framework for achieving a systemic and comprehensive SD assessment that seems (i) to be feasible for practical application, (ii) sensitive for relevant SD issues and (iii) transparent for the addressees of the assessment results. The results show that thermal treatment of the unrecyclable part of the waste stream is the preferred option for waste management when compared to modern landfilling. Furthermore, Eco-indicator 99 method is used to investigate the human health, ecosystem quality and resource use impact categories.

Experimental and modelling studies on a laboratory scale anaerobic bioreactor treating mechanically biologically treated municipal solid waste

The performance of an anaerobic bioreactor in treating mechanically biologically treated municipal solid waste was investigated using experimental and modelling techniques. The key parameters measured during the experimental test period included the gas yield, leachate generation and settlement under applied load. Modelling of the anaerobic bioreactor was carried out using the University of Southampton landfill degradation and transport model. The model was used to simulate the actual gas production and settlement. A sensitivity analysis showed that the most influential model parameters are the monod growth rate and moisture. In this case, pH had no effect on the total gas production and waste settlement, and only a small variation in the gas production was observed when the heat transfer coefficient of waste was varied from 20 to 100 kJ/(m d K)-1. The anaerobic bioreactor contained 1.9 kg (dry) of mechanically biologically treated waste producing 10 L of landfill gas over 125 days.

Dynamic Properties of Municipal Solid Waste and Amplification of Landfill Site

Understanding of the dynamic properties of municipal solid waste (MSW) and the response of waste landfill for cyclic loads are important for safe seismic design and ensuring sustainability of landfills. This study presents estimation of the dynamic properties through field and laboratory tests of MSW landfill and dynamic response of Mavallipura landfill in Bangalore. Both field tests and laboratory tests are used to develop model to represent variation of shear modulus and damping ratio for different strain levels. Ten ground motions are selected based on regional seismicity of landfill site, and detailed site response analysis was carried out considering one-dimensional nonlinear analysis in DEEPSOIL programme. Surface response parameters have been estimated; the surface spectral response varied from 0.6 to 2 g and persisted only for a period of 1 s for most of the ground motions. The minimum and maximum amplifications are 1.35 and 4.05. This study shows that Indian MSW has less shear stiffness and loose filling, may be subject to more amplification for moderate earthquake ground motions, which need to be accounted for seismic design of landfills.