Health and environmental impact of the reuse of treated wastewater for irrigation in the ecological park of the city of Oujda (Eastern Morocco)

Wastewater mainly contains chemical (pesticides, pharmaceuticals, heavy metals, ...) and biological (bacteria, helminths, viruses, ...) risks, and their effects on human health and the environment are very harmful when reused. The bioaccumulation of heavy metals or organic matter in soils irrigated by these waters can affect their quality. On the other hand, the transmission of infections by pathogenic organisms is the main worry, and simple contact with contaminated water can lead to hydric diseases such as typhoid, cholera, etc. With serious and sometimes fatal symptoms such as diarrhea. The reuse of treated wastewater from the Oujda WWTP (around 900 m³/d: i.e., 2.63% of treated water flow) for localized irrigation of the Oujda Ecological Park is a first pilot experiment in the Oriental region. Our study focused on a four-year follow-up (from 2018 to 2021) of the physicochemical and bacteriological quality of the treated wastewater from the WWTP, the drippers in the ecological park's drip irrigation system and the irrigated soil at different plant occupancy levels (under dripper, under tree and between tree rows). The results of treated wastewater analyses showed average concentrations of BOD₅, COD and TSS acceptable in relation to Moroccan reuse standards, at 69.0 mg O₂/l, 170.8 mg O₂/l and 87.4 mg/l respectively. Paradoxically, bacteriological analyses did not comply with Moroccan reuse standards, with an average concentration of 4.10³ CFU/100ml. Analyses of the irrigated soil in the ecological park revealed a spatiotemporal increase in the concentration of fecal coliforms, organic matter and electrical conductivity at the under-drip level and in the Eucalyptus soil occupations and grass during the study period.