Performance of different biocarriers in MBBR and SBBR systems for wastewater treatment: A review

Biocarriers play a critical role in moving bed biofilm reactor (MBBR) and sequencing batch biofilm reactor (SBBR) wastewater treatment systems by providing surfaces for biofilm development. Although a wide variety of carrier materials and geometries are used, the literature remains fragmented, with most studies focusing on individual carriers and lacking a systematic understanding of how carrier characteristics govern treatment performance across different operational conditions. Additionally, review articles comparing biocarrier efficacy in synthetic wastewater systems are limited. This review article synthesizes the performance of various biocarriers in synthetic wastewater treatment and evaluates their efficiency in reducing chemical oxygen demand (COD), ammonia, and total nitrogen (TN). Reported removal efficiencies range from 68% to 96% for COD, up to 99% for ammonia, and 40.0%–97.5% for TN, depending on carrier design and reactor configuration. Carrier-specific surface areas typically range from 250 m²/m³ to 2 800 m²/m³. Analysis reveals that performance is significantly influenced by carrier features such as shape, material, surface roughness, porosity, and specific surface area. Notably, carriers with higher porosity and rough surfaces generally promote superior biofilm formation and pollutant removal, although optimization of surface area may compromise mechanical strength and long-term durability. Operational parameters, such as loading rate, filling ratio, and temperature, also interact with carrier design to determine overall treatment efficiency. While existing studies offer valuable insights, comparative research that links design parameters to treatment performance across varying conditions remains scarce. Future studies should prioritize quantifying relationships between carrier geometry, material properties, and biological activity, as well as developing standardized testing protocols to enable more reliable cross-study comparisons.