Pham M.D.T.Nguyen P.T.Lin C.Visvanathan C.Bui X.T.Mahidol University2026-02-232026-02-232026-04-01Journal of Environmental Chemical Engineering Vol.14 No.2 (2026)22132929https://repository.li.mahidol.ac.th/handle/123456789/115266Microalgal–bacterial granules (MBG) have attracted increasing attention for wastewater treatment due to their high pollutant removal efficiency and low energy demand. This study evaluated the influence of COD/N ratios on MBG properties and treatment performance using four sequencing batch photobioreactors operated at the COD/N ratios of 5, 10, 15, and 20. Although the MLVSS/MLSS ratio remained stable, granule morphology and settling exhibited clear shifts with varying COD/N ratios. The most compact and fast-settling granules were obtained at COD/N = 10, while the lower ratios generated smaller granules. The COD removal rate was stable at 15–17 mg COD/g VSS·d, while the highest ammonium and phosphorus removal rates peaked at COD/N = 5 (1.16 mg NH₄⁺–N/g VSS·d) and COD/N = 20 (0.15 mg TP/g VSS·d), respectively. These results indicate that the COD/N ratio and nutrient loading are critical operational parameters influencing both the physical characteristics of MBG and their nutrient removal performance.Chemical EngineeringEnvironmental ScienceEngineeringArticleSCOPUS10.1016/j.jece.2026.1218362-s2.0-10503023348622133437