Effect of wastewater quality on the performance of a constructed wetland–soil aquifer treatment hybrid system in Palestine

ABSTRACT Graphical abstract shows the CW-SAT setup, water quality results at the inlet and outlets, and reuse and recharge standards. This study evaluated the performance of hybrid horizontal subsurface flow constructed wetlands (CWs) coupled with soil aquifer treatment (SAT) for polishing treated wastewater and assessing suitability for aquifer recharge and crop irrigation. Three parallel CW–SAT systems were operated using secondary effluent from the Birzeit University activated sludge wastewater treatment plant (WWTP) (BZUEff), settled raw wastewater from the Al-Bireh WWTP (ABRW), and secondary effluent from the Al-Bireh extended aeration WWTP (ABEff). CWs treating secondary effluents met Palestinian Class A standards and aquifer recharge requirements for physicochemical parameters (biochemical oxygen demand (BOD) < 20 mg/L, chemical oxygen demand (COD) < 50 mg/L, NH4–N < 5 mg/L, NO3–N < 20 mg/L, and total suspended solids (TSS) < 30 mg/L). Fecal coliform (FC) concentrations were reduced to 36 CFU/100 mL for the ABEff, meeting Class A requirements (<200 CFU/100 mL), and 625 CFU/100 mL for the BZUEff, meeting Class B requirements (<1,000 CFU/100 mL). Subsequent SAT further improved the quality of both secondary effluents, enabling compliance with Class A standards. In contrast, the CW treating settled raw wastewater did not satisfy aquifer recharge requirements. Overall, the integrated CW–SAT system enhanced effluent quality and demonstrated resilience to short-term WWTP underperformance, providing a robust treatment barrier for groundwater protection and aquifer recharge.