The Growth of Escherichia coli in Soil Layers Separating the Soil Surface from the Underground Water Table, in Central Africa: The Hierarchical Influence of the Soil Chemical Characteristics

摘要

The study was carried aimed at assessing the future of E. coli during its transfer through soil layers containing Biodegradable Organic Carbon (BOC) and to classify in order of hierarchy some soil chemical factors that may influence this process from soil surface to the underground water table. A circular hole was dug from the soil surface to the underground water table. This hole crossed 8 different soil layers which were named H_1, H_2,..., H_8 from the soil surface to the underground water table. Experiments were carried out with soil particles with or without BOC. In the absence of BOC, cell retention occurred in all soil layers used. In the presence of BOC, cell retention also, initially occurred and cell growth occurred with a delay which varied from one soil layer to another. Bacterial cell growth from soil layers closer to the surface to those in contact with the underground water table was 1.34, 1.23, 1.22, 1.01, 1.02, 0.86, 0.80 and 0.75/h, respectively. Using the sum of power law function, it was noted that the most 3 factors controlling the cell growth rate in most soil layers are Fe, K, Si, Al and N. The factor K influences in all soil layers. Si also influence in all soil layers with H, excepted. Fe mostly influences in the soil layers H_1, H_2, H_4 and H_6. The factor Al and the factor N mostly influence in the soil layers H, and H_3 and in the soil layers H_5, H_7 and H_8 respectively. During wastewater infiltration through soil layers, bacterial pollutants would be retained on the particles of soil. This retention may be offset by cell growth if the water contains BOC. The process is controlled by various chemicals of the soil, in different magnitude with respect to the soil layer.