Development of a holistic risk assessment methodology and a corresponding computer model for landfill leachate

  • Talib Butt

Student thesis: Doctoral Thesis


This thesis reports on the development of a holistic risk assessment methodology and a corresponding computer model for landfill leachate. Lack of a quantitative risk assessment methodology in a holistic format has prompted this research.

The two main aims of the study are:

• To investigate risk assessments regarding landfills and develop a quantitative methodology of risk analysis for landfill leachate in a holistic manner.

• To produce an electronic representation o f the methodology in the form of a knowledge-base computer model.

In this study, a detailed review of the literature and available computer models on risk analysis for various environmental issues was undertaken. However, this review was narrowed down to focus on risk assessments particularly regarding landfills. The literature review revealed that there is no evidence of the existence of a holistic and yet quantitative risk analysis methodology. This was also found to be the case for computer models reviewed. All existing knowledge and gaps in the knowledge, which could be used as building blocks to assemble and produce a holistic framework of a risk assessment methodology (RAM) specifically for landfill leachate, were investigated and recognised.

The novel knowledge in this study has been generated in terms of adopting, adapting and furthering the existing knowledge with respect to risk analyses of landfill leachate. Where knowledge gaps exist, new concepts have been created to form the holistic RAM, thereby bridging the gaps. In addition, the RAM has been converted into a corresponding computer model, which can assist risk assessors and risk managers in executing risk assessment for a given landfill leachate in a quantitative and interactive manner. The RAM computer model produced was validated by employing a real landfill data provided by a company. A stage-by-stage comparison was drawn between this RAM application and the company’s landfill risk analysis process, thereby identifying discrepancies between the two approaches.

The research work identifies boundaries of the internal relationship between various constituents within the RAM, and the external relationship of the RAM with risk control and risk management. Some examples of the main constituents of the RAM, which are individually developed in this research work, are listed as follows: 1) Baseline Study; 2) Hazard Identification & Categorisation; 3) Exposure Assessment & Exposure Quantification, 4) Concentration Assessment including toxicity assessment; 5) Migration Assessment; 6) Significance Assessment; 7) Uncertainty Assessment; 8) Risk Characterisation comprising Hazard Indices and Risk Quantification. The first four constituents together are referred to as Hazard Assessment in this study, and the last four as Risk Estimation.

The RAM, together with a corresponding computer model, is a novel development, in that no system has utilised this modem risk analysis concept before. The RAM has been designed in such a way that it can be applied to landfill leachate using a novel three-risk-theme approach. These three themes are ‘worst case’, ‘most likely / mean’ and ‘least bad’ scenarios of risk. A methodology, accompanied with a corresponding computer model, now exists for quantifying risk analysis of landfill leachate in a holistic format. This modem risk analysis approach addresses the piece-meal approach that has been employed to landfills to date.
Date of Award2008
Original languageEnglish
SupervisorKehinde Oduyemi (Supervisor)

Cite this