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

Recently, studies have been 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 the biomass in a wastewater treatment plant upgraded from the activated sludge to AGS technology. In the upgraded facility, granulation was obtained quickly and it was observed that the granule morphology depended of the temperature. In the granular biomass harvested at moderate temperatures in the reactor (15°C), the granules with diameters in the range from 125 to 500 μm constituted the largest share (about 60%), while the second-largest biomass fraction comprised the granules with diameters over 1 mm (25%). The analysis of granule diameters carried out in winter (the temperature in the reactor equaled 8°C) showed a decrease in the share of the largest granules and predominance of the granules with diameters in the range from 90 to 355 μm (about 75%). Upgrading the 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 chemical oxygen demand (COD) and phosphorus removal 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 the existing facilities to aerobic granular sludge technology; it was also proven that this technology is an excellent alternative to a conventional activated sludge.