Modelling the Fate and Transport of Microbial Pathogens and Risk Analysis Utilizing Faecal Indicators at Temba Cemetery, Hammanskraal, South Africa

Abstract

The study conducted at Temba Cemetery in Hammanskraal, South Africa, sought to comprehend the complexities of microbial pathogen fate and transport within burial sites. Aiming to address environmental contamination and associated health risks, the investigation focused on modelling pathogen movement using faecal indicators, specifically E. coli. Real-time observations and assessments were possible due to Temba Cemetery's active use since the late 1960s, providing a dynamic research setting. The site visit identified significant factors impacting the study, such as waterlogged graves and notable groundwater seepage, influencing faecal indicator distribution and pathogen movement. Drilling operations established ten monitoring wells, crucial for assessing groundwater levels, hydraulic conductivity, and diverse testing protocols. Hydraulic tests unveiled variations in soil types, affecting pathogen migration rates, while groundwater flow calculations determined velocities across the cemetery. The geometric mean of hydraulic conductivity and groundwater flow velocity from bail tests was calculated to be 0.0528 and 3.4803 m/day, respectively. Water quality analyses identified elevated faecal coliform (i.e. 5 000 colonies/100 ml) and E. coli (i.e. 5 000 to 5 300 colonies/100 ml) counts in burial zones and stream, surpassing safety thresholds. Tracer tests informed a sophisticated Advection-Dispersion Equation (ADE) model using Sauty (1980) equation, refining pathogen transport simulations. Utilizing the breakthrough curves (BTC) for two tracer tests, longitudinal dispersivity of 5.1 and 2.3 m; velocities of 18 and 6 m/day and effective porosities of 0.02 and 0.05 were calculated from model fitting. However, discrepancies between simulated and observed velocities highlighted model limitations, necessitating continual refinement. Quantitative Microbial Risk Assessment (QMRA) indicated potential exposure routes, emphasizing the need for further investigation to mitigate health risks. Varied groundwater velocities highlighted the complex hydrogeological system's influence on pathogen transport. This investigation explained the challenges in predicting pathogen fate and transport, highlighting the need for continuous model refinement. Discrepancies identified emphasized the complexities in modelling pathogen movement, demanding ongoing model validation and refinement to improve accuracy. Recommendations include improved burial practices, community engagement, collaborative efforts, regular monitoring, and in-depth hydrogeological studies. These findings underscore the critical role of accurate modelling in addressing health risks and guiding environmental health management within cemetery environments.