Experimental and Modelling Approaches for the Assessment of Chemical Impacts of Leachate Migration from Landfills: A Case Study of a Site on the Triassic Sandstone Aquifer in the UK East Midlands

Abstract

Current risk-based methods for assessing the effects of landfill leachate migration on groundwater resources are conservative and generalised. Cost-effective and practical strategies are required which can robustly determine the potential for contaminant attenuation on a site-specific basis. In this paper laboratory column experiments and reactive transport modelling are evaluated as a combined approach for assessing the chem'ical impact of leachate migration in the Triassic Sandstone aquifer. The results are compared with field data for a landfill in the East Midlands. Columns of aquifer sandstone were flushed sequentially with groundwater, followed by acetogenic or methanogenic leachate to simulate chemical interactions occurring during leachate loading episodes. The key contaminants in leachate (NH 4 , heavy metals, organic fractions) were attenuated by ion exchange, redox reactions, sorption and degradation. These processes produce a consistent hydrochemical signature which may help identify the extent of leachate migration in the aquifer. The laboratory results largely replicate those found in the field system, and the behaviour of inorganic contaminants during leachate flushing of the aquifer columns can be described by the reactive transport model. The experimental and modelling approach presented represents a powerful tool for risk assessment and prediction of leachate contaminant fate at unlined and lined landfills.

Towards prediction of saturated-zone pollutant movement in groundwaters in fractured permeable-matrix aquifers: the case of the UK Permo-Triassic sandstones

“…The laboratory experiments of Thornton et al (1995Thornton et al ( , 2000bThornton et al ( , 2005 suggest that NH4 § exchange behaves very similarly, as might be expected, to K § exchange, and this seems to be the case in the field too (Lewin et al 1994). Usually a Kd approach is applied when predicting NH4 migration (Erskine 2000;Gillespie et al 2000;Jones 2001;Adey 2004;Buss et al 2004), and the experiments of Thornton et al (2000b) show that breakthroughs for NH4 § (and K +) can indeed be described by retardation factors: geochemical modelling work generally supports this conclusion, but also suggests that the appropriate Kd value is very difficult to predict/ measure without extensive knowledge of the system (Clarke 2005).…”

Method of evaluating the impact of landfill leachate on groundwater quality

“…Such methods are usually time-consuming and expensive, particularly if they are applied in closed objects. The degree of pollution of underground waters can be estimated based on model test results (Burn and Engesgaard 2002 ; Thornton et al 2005 ). Model tests should be performed taking into account the conditions of landfill location, qualitative and quantitative parameters of landfill leachate, and underground water (Szymański and Janowska 2016 ; Tsanis 2006 ; Tałałaj and Dzienis 2007 ; Zhu et al 2013 ).…”