Wastewater treatment and industrial reuse in a semi-arid mining basin: Performance and energy efficiency of the Khouribga wastewater treatment plant (Morocco)
Abstract
Morocco’s structural water scarcity has increased interest in treated-wastewater reuse for phosphate processing. This study evaluates the 2025 performance and energy intensity of the Khouribga activated-sludge wastewater treatment plant using 365 daily operator records. Concentration removal, inlet and outlet mass loads, and volumetric and COD-mass-based energy indicators were recalculated with explicit Qin/Qout definitions. Exploratory correlations were adjusted using the Benjamini–Hochberg false-discovery-rate procedure, while time-ordered re-gressions used Newey–West heteroskedasticity-and autocorrelation-consistent standard errors with a 7-day lag. Mean concentration removals were 91.3% for total suspended solids (TSS), 90.1% for chemical oxygen demand (COD), and 94.3% for five-day biochemical oxygen demand (BOD 5 ). All available TSS, COD and BOD 5 measurements met the Moroccan general domestic-discharge limits. However, only 12.1%, 34.2% and 38.4% of the corresponding observations met the more stringent historical tertiary-treatment objectives reported for this plant; these objectives are performance benchmarks rather than statutory or currently verified OCP specifications. The summer–winter COD-removal difference was 2.01 percentage points (HAC p = 0.039), whereas temperature was not independently significant in the multivariable model. Flow explained little variation in pollutant removal. Mean volumetric energy intensity was 0.687 kWh/m³ for all days and 0.660 kWh/m³ after excluding two very-low-flow sensitivity observations. Mean COD-mass-based intensity was 1.216 kWh/kg COD removed. Their daily cor - relation decreased from r = 0.392 in the complete series to r = 0.035 in the sensitivity set. The results demonstrate high average removal but also show that legal discharge compliance, attainment of stringent reuse targets, and energy benchmarking are distinct questions. The supplied code and supplementary outputs provide a reproducible workflow for future plant audits.