A new system for groundwater contamination hazard rating of landfills

In developing countries, several unregulated landfills exist adjacent to large cities, releasing harmful contaminants to the underlying aquifer. Normally, landfills are constructed to hold three types of waste, namely hazardous waste, municipal solid waste, and construction and demolition waste. Hazardous waste and municipal solid waste landfills are of greater importance as these pose greater hazard to groundwater, in comparison with landfills holding waste from construction and demolition. The polluting landfills need to be prioritized to undertake necessary control and remedial measures. This paper assesses existing site hazard rating systems and presents a new groundwater contamination hazard rating system for landfills, which can be used for site prioritization. The proposed system is based on source-pathway-receptor relationships and evaluates different sites relative to one another. The system parameters have been selected based on literature. The Delphi technique is used to derive the relative importance weights of the system parameters. The proposed system is compared with nine existing systems. The comparison shows that the site hazard scores produced by the existing systems for hazardous waste, municipal solid waste, and construction and demolition waste landfills are of the same order of magnitude and tend to overlap each other but the scores produced by the proposed system for the three types of landfills vary almost by an order of magnitude, which shows that the proposed system is more sensitive to the type of waste. The comparison further shows that the proposed system exhibits greater sensitivity also to varied site conditions. The application of different systems to six old municipal solid waste landfills shows that whereas the existing systems produce clustered scores, the proposed system produces significantly differing scores for all the six landfills, which improves decision making in site ranking. This demonstrates that the proposed system makes a better tool for prioritization of landfills for adopting control measures and remediation.