Evaluation of Environmental Pollution and Microbial Treatment of Shallow Groundwater in El Omayed Area, Egypt.

Abstract

In the last few years, the northwestern coastal zone of Egypt has been affected by many stresses that impact its water resources, leading to undesirable consequences related to water quantity and quality. This paper aims to evaluate the possible contamination sources of shallow aquifers in the El-Omayed area, Egypt, that are causing its deterioration; this was achieved through an integration of hydrochemical and isotopic techniques, an assessment of the undesirable consequences of potential toxic metals (PTMs) on human health risk as a result of direct water consumption, and finally, the application of biological treatment in the remediation of some metal contamination. The chemical composition, environmental isotopes (δ18 O and δ2 H), and microbial analyses were analyzed from 13 collected water samples. Approximately 20% of the groundwater samples were classified as fresh water, and the rest were classified as slightly saline to moderately saline. Stable isotopes proved the contribution of the El Sheikh Zoied canal (which is mainly recharged from the Nile system) as a recharge source. The toxicity of PTMs (Cd, Cu, Co, Cr, Pb, Zn, B, and Fe) was evaluated on the basis of their exceedance values. It was proven that the majority of the groundwater samples were contaminated, which might be attributed to natural and anthropogenic actions in the study area; however, according to human health risk exposure assessment calculations, there is no human cancer risk posed via ingestion of drinking groundwater. The total bacterial count was determined for all water samples; autochthonous microorganisms were capable of removing heavy metals in the polluted water sample. The bacterial strain M52, which was identified by 16S rRNA sequencing as Stenotrophomonas rhizophila, showed the best results, by removing 75% and 65% of the initial concentrations of Fe and B, respectively. The results indicate that this bacterial strain may be useful and represents an environmentally friendly method to remove pollutants and heavy metals from contaminated water. Integr Environ Assess Manag 2020;16:461-471. © 2020 SETAC.