A study on the impact of wastewater on the quality water quality from certain wells in the Oued Amlil region of the Taza province, Morocco

Olive mill wastewater, a byproduct of olive oil production, poses a major environmental challenge for Mediterranean countries like Morocco. These residues are rich in polyphenols with notable antimicrobial properties. This study aimed to investigate the impact of anthropogenic factors on the quality of certain wells in the Oued Amlil region of the Taza province, Morocco. It was carried out during two distinct periods by sampling water from six wells: P1, P2, P3, P4, P5 and P6. The first period occurred during the winter season of December 2022, when olive crushing operations for oil production were at their peak. The second period took place in the summer (August 2022), when the activities of the oil mills were stopped. The objective is to assess microbiological quality by determining the microbial load in total germs at 37°C (TG), Fecal Coliforms (FC), Total Coliforms (TC), and Fecal Streptococci (FS), as well as performing a polyphenol assay. The analysis results showed high concentrations of TG (Maximum value = 3100/100ml), FC (Maximum value = 910/100ml), TC (Maximum value = 7120/100ml), and FS (Maximum value = 7000/100ml) in wells P1, P2, and P5, although they are not located on the flow path of groundwater contaminated by the Innaouene River and the local olive oil mills. However, despite their location along this axis, wells P3, P4, and P6 show lower contamination levels. In order to identify similarities between different water sources and/or different points of contamination acquisition, principal component analysis (PCA) was applied to the collected data and  showed a significant negative correlation between polyphenols and bacteriological parameters, confirming the hypothesis of polyphenols' bactericidal effect on fecal bacteria. In addition, the degree of contamination varies from one well to another depending on their location with the direction of flow of water in the groundwater and the proximity of sources of pollution