Performance Optimization of Moving-bed Biofilm Reactor ( MBBR) Systems for Municipal Wastewater in Egypt: Impact of change Hydraulic Retention Time and Dissolved Oxygen

Egypt is among the most climate-vulnerable countries in the MENA region, facing increasing stress on freshwater resources, particularly for agriculture. Therefore, innovative and efficient municipal wastewater treatment technologies are urgently needed. The Moving Bed Biofilm Reactor (MBBR) represents a promising solution due to its compact design, operational simplicity, low sludge production, and high-quality effluent. This study investigates the performance of lab-scale MBBRs treating municipal wastewater under Egyptian conditions, with a focus on varying Hydraulic Retention Times (HRTs) of 4, 6, and 8 hours, and two dissolved oxygen (DO) levels: low (2.3 mg/L) and high (>4.5 mg/L). Results demonstrated excellent removal efficiencies: COD (87.4–94.5%), BOD₅ (87.6–94.4%), and TSS (83.4–92.6%). Residual nutrient levels (TKN, NH₄⁺, and TP) ranged from 13.7–22.4 mg N/L, 2.7–14.1 mg N/L, and 1.07–2.65 mg P/L, respectively. Higher DO improved performance, but even under low DO, effluent quality at 6 and 8 hours HRT met reuse and discharge standards. These findings suggest that MBBRs can be efficiently operated at moderate HRT and low DO, offering a sustainable and cost-effective option for wastewater treatment and water reuse in arid regions like Egypt.