Impact of feeding strategy on the performance and operational stability of aerobic granular sludge treating high-strength ammonium concentrations

Abstract

We evaluated the impact of feeding strategy on the performance and operational stability of aerobic granular sludge (AGS) treating high-strength ammonium concentrations. Synthetic wastewater with characteristics close to those found in sanitary landfill leachate was applied in sequential batch reactors (SBR) for biomass cultivation. In this sense, differing only in the feeding method, three identical 7.6 L (working volume) reactors were operated with the same total cycle time of 12 h duration. In R1 and R2, it was adopted feeding in the anaerobic period with a duration of 20 min (fast) and 40 min (slow), respectively. In R3, feeding was distributed throughout the cycle (step-feeding), half of which was introduced initially, and the other half divided equally with 40 and 60% of the cycle. Substrate distribution throughout the cycle (R3) minimized three of the biggest problems faced when treating leachate in AGS systems: granules' stability, biomass retention, and nitrite accumulation. Besides, compared to fast (R1) and slow (R3) feeding, this mode of operation obtained the best total phosphorus (TP, 53%) and total nitrogen (TN, 92%) removals, without any nitrite or nitrate accumulations. COD removals were very similar in R2 and R3, but TN and TP removals were significantly greater in R3. Therefore, the feeding method directly interferes with the performance, granules' characteristics, and system stability. The results obtained in this research can be used in future works applying the AGS technology for sanitary landfill leachate and other complex wastewaters treatment.