Abstract
This study assessed the groundwater quality around two municipal solid waste landfill sites, in the city of Bloemfontein, Free State Province, South Africa. The two landfill sites are located in two contrasting geological terrains, with both lacking some basic facilities found in a well-designed landfill. A total of eight groundwater samples were collected from pollution monitoring boreholes near the two landfill sites, with five samples representing the northern landfill site and three samples representing the southern landfill site. The samples were collected in the autumn and winter seasons to assess any possible seasonal variations. They were analysed for physicochemical (pH, electrical conductivity (EC), total dissolve solids (TDS), chemical oxygen demand (COD) and total organic carbon (TOC)) and microbiological parameters (Escherichia coli, total coliform). The results of the analysis showed that the waters from both landfills were generally dominated by Ca, Mg, SO4, and HCO3 ions. Some of the major anions and cations in the water samples were above the South African National Standard (SANS241:2015) and World Health Organisation (WHO) permissible limits for drinking water. Majority of the boreholes had total dissolved solids and electrical conductivity values exceeding the SANS 241:2015 and WHO permissible limits. Piper trilinear plots for the two landfill sites showed that Ca(Mg)HCO3 water type predominates, but Ca(Mg)SO4 and Ca(Mg)Cl were also found. These water types were further confirmed with expanded Durov diagrams, indicating that that the boreholes represented a water type that is seldom found which is undergoing ion exchange, typical of sulphate contamination. From the SAR diagrams, boreholes in the northern landfill site had a high salinity hazard with only one borehole in the southern landfill site having a high salinity hazard. The geology was found to play a significant role in the distribution of contaminants into the groundwater systems in the study area. The study concluded that the northern landfill site had a poorer water quality in comparison to the southern landfill site based on the analysed physicochemical parameters. However, the southern landfill site showed significant microbial contamination, due to the elevated amount of E. coli and total coliform concentrations. The high permeability of the weathered dolerites in the northern landfill site might have enabled the percolation of contaminants into the groundwater resulting in the poorer water quality.
Highlights
Water is regarded as an essential requirement of life which has been considered more as an economic resource than a social good [1]
TDS concentrations varied across the two landfill sites with boreholes in the northern landfill site having the highest TDS concentrations over the two seasons (Table 2)
Three groundwater samples were taken from the southern landfill boreholes, while five boreholes samples were taken from the northern landfill boreholes
Summary
Water is regarded as an essential requirement of life which has been considered more as an economic resource than a social good [1]. Urbanisation, irrigation and domestic activities have resulted in the overexploitation of available water resources of which surface water has been the most reliable source of water [1]. According to Pietersen et al [2], surface water resources in South Africa have over the years been unable to meet the country’s water demands, and groundwater has become a potential and convenient source of drinking water. Groundwater is considered as a safe source of drinking water because it is abstracted with low microbial load, and minimal treatment is required before consumption [3]. The contamination of groundwater resources either by natural or anthropogenic sources, degrades their quality rendering it unfit for use
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