Environmental negative and positive impacts of treated sewage water on the soil: A case study from Sohag Governorate, Egypt

This study aims to investigate the environmental negative and positive impacts of treated sewage water on the soil at two sites (El Cola and El-Deir), Sohag Governorate, Egypt. The changes in soil properties and nutrient contents due to prolonged treated sewage water irrigation were also studied compared to non-irrigated soils on the subsurface layers. The results indicate that most of the soil samples in El Cola and El Deir area - Sohag governorate have a sandy texture. soil pH values of the studied area varied between 7.1 and 8.23 In most cases, pH of the surface layers was lower than that of the subsurface ones, especially for those irrigated by sewage water for a long time (20, 19, 29 and 21 years). The ECe values of the soils (El Cola and El Deir) ranged from 0.7 to 1.4 ds/m with an average value of 1.1 dS/m. Most of the cultivated soil samples had low salinity (ECe < 4dS/m). In most of the sewage water irrigated soils, the surface layers showed higher ECe values than the subsurface ones due to the salt accumulation of this sewage water. Moreover, soil organic matter content tended to decrease with depth and soil prolonged irrigated with sewage water increased the soil organic matter compared to the short time irrigated soil. In general, the results also showed that increases in the total N, available phosphorus and available K of all studied soils irrigated with sewage water occurred compared to those of the non-irrigated soil. The soils irrigated with sewage water for a long time were higher than those under short-term use. A positive significant correlation between nutrients (total N and available K) and soil organic matter was found and it suggests that sewage irrigation helps to increase levels of soil organic matter and hence improve the fertility status of the soil.,Regarding to heavy metals, the soil contents of all investigated heavy metals (Cd, Zn, Cu, Pb and Ni) are lower than their corresponding values of the common range, background and average concentrations for world soils. However, in term of contamination factor (CF), the soil samples have CF values ranged from 1 to 48 in El-Cola and from 0.6 to 19 in El-Deir, indicating the pollution levels are in the range of low or moderate to very high levels Among all metals, Pb showed the highest values of CF (48 mg per kg).