K5/1766 - Field investigations to study the fate and transport of LNAPLs in groundwater
Funded by: Water Research Commission
April 2007 – March 2011

Partner organisations: University of the Free State; UKZN School of Environmental Hydrology , GeoMeasure Guateng

Project description
In 2007, the Pollution Research Group joined the Institute of Groundwater Studies at the University of the Free State on a study to research the fate and transport of Light Non-aqueous Phase Liquids (LNAPL) in groundwater in South Africa. LNAPLs are organic chemicals that exist in a lighter-than-water immiscible phase when released into the environment. They include a number of organic products and represent some of the most widely used potential environmental contaminants. While existing research provides a valuable knowledge base for understanding the fate and transport of LNAPLs, limited research has been carried out in South Africa. This project examined LNAPLs in the specific geologic and climactic conditions of South Africa. 

The aims of this study were to characterise the fate and transport of identified priority LNAPLs in flagship field sites, examining the mechanisms by which LNAPL pollutants enter groundwater flow systems; their fate in the subsurface; and the applicability of different remedial techniques in South Africa. In addition, the study aimed to develop reliable predictions of the transport of LNAPLs within the South African flow systems; and from these results develop appropriate guidelines for LNAPLs which are appropriate to South African conditions.

The study involved seven steps, including an extensive literature review, data collection on the environmental and infrastructural conditions of the sites, assessment of the vadose, saturated and unsaturated zones at each site, investigation into microbial populations at each site, the development of conceptual and mathematical models to predict the migration of LNAPLs in the environment, evaluation of different remedial solutions, and workshops with key stakeholders to share learnings. The research was carried out in a phased approach, in which a preliminary investigation of each site provided the basis for further exploratory investigations to determine the nature and extent of contamination and the geology, geochemistry, hydrogeology and hydrology of each site. The project set out to produce several guidelines on monitoring LNAPL sites, risk-based management and remediation, and characterisation of LNAPL sites that incorporate source, pathways and receptors. 

Pollution Research Group was involved specifically in conducting research on the Island View site and the Chatsworth site both located in eThekwini Municipality.