Treatment Efficiency and Characteristics of Biomass in a Full-Scale Wastewater Treatment Plant with Aerobic Granular Sludge

Recently, research are carried out on an implementation of aerobic granular sludge (AGS) technology in full-scale wastewater treatment plants. The aim of the work was to evaluate the effectiveness of organic, phosphorus and nitrogen compounds removal from municipal wastewater and to characterize biomass in a wastewater treatment plant upgraded from activated sludge to AGS technology. In the upgraded facility, granulation was obtained quickly and it was observed that granule morphology depended of the temperature. In the granular biomass harvested at moderate temperatures in the reactor (15°C), the largest share (about 60%) constituted granules with diameters in the range from 125 to 500 μm, while the second-largest biomass fraction constituted granules with diameters over 1 mm (25%). Analysis of granule diameters carried out in winter (temperature in the reactor 8°C) showed a decrease in the share of the largest granules and predominance of granules with diameters in the range from 90 to 355 μm (about 75%). Upgrading municipal wastewater treatment plant from activated sludge to aerobic granular sludge significantly improved the settling properties of the biomass and efficiency of wastewater treatment. The average efficiency of removal of chemical oxygen demand (COD) and phosphorus increased by about 10% and 20%, respectively, while ammonium nitrogen was completely oxidized, regardless of the season. After modernization, the concentration of nitrates in the effluent increased significantly to about 3-6 mg/L. The results of the study show that it is possible to effectively upgrade existing facilities to aerobic granular sludge technology and that this technology is an excellent alternative to a conventional activated sludge