Assessment of treatment efficiency and potential marine environmental risk of petrochemical effluents from the GL3-Z Refinery in Arzew, Algeria

This study presents a 27-month monitoring (January 2021–March 2023) of treated industrial effluents from the GL3-Z refinery wastewater treatment plant (WWTP) in Arzew, Algeria. A total of 27 samples were analyzed using standard methods to investigate physicochemical parameters from the industrial effluent, including temperature, pH, total suspended solids (TSS), chemical oxygen demand (COD), biochemical oxygen demand over 5 days (BOD₅), phosphate (PO₄³⁻), cyanide (CN⁻) and concentrations of selected heavy metals ions such as Cr(VI), Fe(II), Cu(II), Zn(II). The obtained results were: temperature (15.10–28.13 °C), pH (4.04–5.97), TSS (8.00–272.00 mg/L), COD (15.50–317.33 mg/L), BOD₅ (0.80–108.93 mg/L), PO₄³ ⁻(36.75–103.95 mg/L), Zn(II) (0.037–0.90 mg/L), Fe(II) (0.16–26.30 mg/L), Cr(VI) (0.002–0.18 mg/L), Cu(II) (0.02–25.57 mg/L), and CN⁻ (0.001–0.16 mg/L). The major findings of this research work reveal the ineffectiveness of the treatment system employed by the WWTP in reducing TSS, COD, BOD₅, PO₄³ ⁻, Cu(II), Zn(II), Cr(VI), and CN⁻ levels to comply with the regulatory standards of the Ministry of Land Planning and Environment of Algeria, the World Bank Group, and the Australian and New Zealand Environment and Conservation Council. The results showed that effluents from this WWTP are potential sources of marine pollution and call for urgent improvement of WWTP operations to ensure safe effluent discharge.