Multivariate and index-based evaluation of long-term reclaimed wastewater quality and reuse suitability

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 ۲۰۱۶–۲۰۲۵ 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 ۸۹۳:۲۰۲۱. 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 ۳۰ campaigns using ordinary least-squares regression, reporting slope, coefficient of determination, and p-value; Escherichia coli was evaluated on the log۱۰ scale. Principal component analysis, hierarchical cluster analysis, and Environmental Protection Agency Positive Matrix Factorization ۵.۰ characterized covariance, similarity, and stable effluent-quality profiles.FINDINGS: Average parameter-level compliance ranged from ۵۰ to ۶۵ 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 ۱۰۰. Subsequent sensitivity evaluations revealed that Escherichia coli drove approximately ۹۹.۹۹ 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 ۱۰۰, 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 ۸۹.۵۴ percent of variance through four components, and positive matrix factorization resolved four stable profiles contributing ۵۴.۰, ۲۰.۳, ۱۶.۷, and ۹.۱ 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 ۸۹۳:۲۰۲۱ 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.

کلیدواژه ها:

Index-based evaluation ، Jordan ، Multivariate methods ، Positive matrix factorization ، Reclaimed wastewater ، Source apportionment.