Environmental risks associated with the leakage of untreated wastewater in industrial Areas

MANY countries around the world are forced to use wastewaters in plant production and their codes regulate such usage. However, these policies are not enough to stop their indirect impacts on the ecosystem. In Shobra El-Khema (Egypt), canals and agricultural drains still receive massive amounts of untreated industrial wastes and; therefore, the Egyptian government prohibited the usage of this wastewater for crop production. Alternatively, farmers use well water for irrigation; however, these shallow wells still receive wastewater leakage from the main drains and this probably possesses negative implications on the environment immediately or at least in the long-term. Accordingly, water, soil and plant samples were collected from these wastewater - contaminated areas wherein their contents of Fe, Mn, Zn, Cu, Cd, Co, Ni and Pb were investigated. The comprehensive pollution index (CPI) was then calculated for potentially toxic elements (PTEs) in water of both the main drain and the well waters (during the winter and summer seasons of 2016, 2017 and 2018). Results indicate that there was no significant variation in CPI between these two sources (P<0.05). On the other hand, ammonium bicarbonate–diethylene triamine penta acetic acid (AB-DTPA) extractable PTEs and their total contents increased progressively and significantly within the subsequent soil layers during the three successive years of study (P<0.05). In this concern, the highest concentrations of PTEs were detected within the top (0-15 cm) soil layer, while decreased with increasing soil depth. The grown plants nearby the main drain (especially leafy vegetables) accumulated high concentrations of PTEs in their shoots and these concentrations exceed the permissible levels of Pb and Cd. On the other hand, levels of soil pollution with PTEs decreased considerably with increasing the distance from the main drain in spite of that slight to moderate levels of soil pollution with PTEs were detected at 1000 m apart from the main drain. Thus, leakage of untreated wastewaters possesses high ecological risks that extents to a distance of one kilometer apart from the main drain.