Groundwater contamination at a landfill: a case study of coastal park landfill, Cape Town

Baderoon, Muneeb

Groundwater contamination at a landfill: a case study of coastal park landfill, Cape Town

Master Thesis

2022

Abstract

The extent of groundwater pollution from landfills varies throughout the year. Studies have shown that rainfall is the greatest contributor to nutrient pollution in groundwater. Therefore, groundwater monitoring that is based on predetermined schedules and fails to consider the effects of rainfall, may not adequately represent the condition of the groundwater or the effects the landfill has on groundwater. The subsequent management of landfills will, in such cases, be based on a limited understanding of the groundwater condition. This study aimed to determine the fluxes in groundwater quality at the Coastal Park landfill in Cape Town, South Africa, and to analyse how groundwater quality changes with local rainfall. Changes in borehole water levels, pH, conductivity, dissolved oxygen, ammonia, nitrate and phosphate were analysed over consecutive weeks of seasonal rainfall from boreholes that were upstream and downstream of two large landfill cells; one being lined and the other unlined. The results were compared to rainfall over the same period and the results showed nutrient concentrations in the groundwater were influenced by several factors, the most significant being rainfall. The concentrations of each selected nutrient displayed widely different variation patterns over the monitoring period. Monitoring results from any single sampling event was shown to be merely a snapshot in time and therefore could not be accepted as a wholistic representation of groundwater pollution. Groundwater monitoring results obtained from predetermined low frequency sampling schedules should then be interpreted in the context of the prevailing intra-seasonal rainfall patterns and sampling locations if the groundwater monitoring results are to be understood correctly. The location of groundwater monitoring boreholes significantly affected the lag between rainfall and groundwater nutrient pollution changes and trends. The results further suggest that any groundwater monitoring schedule that is based on a small number of predetermined sampling dates cannot accurately describe the rate and direction of groundwater nutrient concentration trends and will not identify the peak concentrations of all significant pollutants.

Keywords

Environmental and Geographical Science

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