Effect of Effluent Recirculation on the Performance of an Anaerobic Baffled Reactor in Municipal Wastewater Treatment: A Modeling Approach

Nadeem Ullah, Zeshan Sheikh (), Sarah Bader Alotaibi, Mujahid Khan and Aziz Ahmad
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Nadeem Ullah: Institute of Environmental Sciences and Engineering, School of Civil and Environmental Engineering, National University of Sciences and Technology (NUST), Sector H-12, Islamabad 44000, Pakistan
Zeshan Sheikh: Institute of Environmental Sciences and Engineering, School of Civil and Environmental Engineering, National University of Sciences and Technology (NUST), Sector H-12, Islamabad 44000, Pakistan
Sarah Bader Alotaibi: Department of Teaching and Learning, College of Education and Human Development, Princess Nourah bint Abdulrahman University, Riyadh 11671, Saudi Arabia
Mujahid Khan: Department of Civil Engineering, University of Engineering and Technology, Peshawar 25000, Pakistan
Aziz Ahmad: Department of Civil Engineering, City University of Science and Information Technology, P.O. Box 24370, Peshawar 25000, Pakistan

Sustainability, 2025, vol. 17, issue 9, 1-24

Abstract: This study examined the effect of effluent recirculation on the performance of an anaerobic baffled reactor (ABR) in treating municipal wastewater under mesophilic steady-state conditions. Although effluent recirculation is proposed to enhance ABRs’ performance, its benefits remain inconclusive, highly dependent on wastewater characteristics, and inadequately understood during steady-state conditions. Utilizing the GPS-X computer application, an innovative modeling and simulation approach was employed to evaluate an ABR’s performance in removing chemical oxygen demand (COD) and total suspended solids (TSS). Sensitivity analysis was utilized to refine critical stoichiometric, kinetic, and operational parameters for precise model calibration and validation, thus enhancing the model accuracy. The average absolute relative error (ARE) and Thiel inequality coefficient (TIC) were employed for model calibration and validation. The effect of effluent recirculation on the treatment behavior of the reactor was investigated through model predictions, considering recirculation ratios of 10%, 20%, and 30%. The results showed that effluent recirculation had a limited effect on ABR performance at HRTs of 24, 18, and 12 h, with COD removal efficiency (RE) improving by up to 2.1%, and TSS RE by up to 5.7%. However, at an HRT of 8 h, COD RE declined from 65% (no recirculation) to 61.6% at a 30% recirculation ratio, while TSS RE slightly improved at 10% but decreased by 4.1% at 30%. This study concluded that, under mesophilic conditions, effluent recirculation may not be an effective strategy for improving ABR performance in municipal wastewater treatment, potentially increasing operational costs due to an increase in energy consumption for effluent recirculation.

Keywords: anaerobic baffled reactor; effluent recirculation; GPS-X modeling; model predictions; municipal wastewater treatment (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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