BACKGROUND AND OBJECTIVES: Reclaimed wastewater is important in water-scarce regions, but safe reuse requires sustained effluent quality. The study objectives were to evaluate the quality and reuse potential of effluent discharged from the Karak domestic wastewater treatment plant in Jordan over the 2016–2025 period. The investigation employed a comprehensive framework integrating regulatory standards, water quality indices, temporal trend evaluations, multivariate statistical techniques, and positive matrix factorization.METHODS: Seventeen physicochemical and microbiological parameters were assessed against Jordanian Standard 893:2021. Water quality index and water pollution index were applied as supplementary screening tools, and parameter-contribution and sensitivity analyses evaluated the magnitude of influence exerted by specific variables and the underlying weighting framework. Linear trends were estimated from 30 campaigns using ordinary least-squares regression, reporting slope, coefficient of determination, and p-value; Escherichia coli was evaluated on the log10 scale. Principal component analysis, hierarchical cluster analysis, and Environmental Protection Agency Positive Matrix Factorization 5.0 characterized covariance, similarity, and stable effluent-quality profiles.FINDINGS: Average parameter-level compliance ranged from 50 to 65 percent across reuse and discharge categories, with limitations from residual organic matter, suspended solids, nutrients, bicarbonate, phenol, fats, oils and grease, and Escherichia coli. Across all categories, water quality index values surpassed 100. Subsequent sensitivity evaluations revealed that Escherichia coli drove approximately 99.99 percent of the weighted index for Class D irrigation and groundwater recharge, whereas phenol dominated Classes B and C. Equal weighting reduced mean Class C water quality index below 100, confirming weighting sensitivity without changing the regulatory compliance conclusion. Water pollution index decomposition also showed dominant Escherichia coli influence. Significant decreasing linear trends occurred for biochemical oxygen demand, chemical oxygen demand, total dissolved solids, total suspended solids, total nitrogen, phosphate-phosphorus, chloride, and sodium adsorption ratio, whereas dissolved oxygen, phenol, and nitrate-nitrogen increased. Principal component analysis explained 89.54 percent of variance through four components, and positive matrix factorization resolved four stable profiles contributing 54.0, 20.3, 16.7, and 9.1 percent.CONCLUSION: Index magnitudes were strongly affected by restrictive standards and dominant parameters, while temporal trends indicated directional change without establishing causal treatment mechanisms. Direct Jordanian Standard 893:2021 compliance should remain the primary basis for reuse decisions. Confirming underlying causal mechanisms or targeted treatment interventions necessitates higher-frequency monitoring protocols that encompass influent, hydraulic, operational, and source-specific metrics.