Contaminated drinking water poses significant environmental health risks, particularly in developing countries like Nigeria, where inadequate treatment and microbial pollution of groundwater remain major challenges. This study investigates bacterial movement in contaminated groundwater using column experiments to assess filtration efficiency under varying conditions.
Sewage samples were collected, and bacterial isolates (Escherichia coli, a rod-shaped bacterium, and Staphylococcus aureus, a coccoid bacterium) were selected based on biochemical characterization and morphology. A laboratory-scale column system was packed with sterile sand of different particle sizes (600 µm, 425 µm, 212 µm, and 150 µm) and depths (10 cm, 20 cm, 40 cm, and 50 cm). Bacterial suspensions were injected into the column, followed by intermittent sterile water elution. Effluent samples were collected and analyzed microbiologically to determine bacterial retention.
Results showed that bacterial recovery decreased with increasing sand depth and decreasing particle size. The highest retention occurred at 50 cm depth with 150 µm sand, while the lowest retention was observed at 10 cm with 600 µm sand. Sequential elution further reduced bacterial loads, with the first eluent containing the highest concentration and the fifth the least. Statistical analysis confirmed a significant negative correlation between bacterial recovery and sand depth (p < 0.05). E. coli exhibited greater mobility than S. aureus, suggesting shape-dependent transport behavior.
These findings imply that bacteria from septic tanks and pit latrines can migrate through subsurface layers, reaching groundwater sources and posing fecal–oral disease risks. Since aquifer remediation is often impractical, preventive measures, such as proper waste disposal and optimized well placement, are critical for safeguarding groundwater quality. This study underscores the need for improved water management policies in Nigeria to mitigate public health threats from microbial contamination.
