Simultaneous removal of carbon, nitrogen, and phosphorus from landfill leachate using an aerobic granular reactor

In this study, aerobic granular reactor (AGR) was used to treat landfill leachate by changing the concentrations of chemical oxygen demand (COD) (668 ± 110-1149 ± 93 mg/L), ammonia (NH3–N) (30 ± 3.3-48 ± 1.3 mg/L), and phosphorus (PO4–P) (147 ± 18-221 ± 17 mg/L). The average COD removal was gradually reduced from 81 to 75%, increasing COD concentrations from 668 ± 110 to 1149 ± 93 mg/L. In phase I, the maximum removal of COD (94%) and NH3–N (85%) were observed at influent concentrations of 668 ± 110 mg/L and 30 ± 3.3 mg/L, respectively. Significant removal of PO4–P was observed, resulting in a maximum of up to 87%, further reducing up to 34% due to an increase in influent PO4–P concentration. The SVI30 reduced from 77 mL/g to 24.15 mL/g towards the end of phase III indicates the formation of granular biomass. The stability of AGR was also investigated in extreme conditions like shut-down and shock-loading phases. The treatment of real leachate diluted with wastewater (∼20:80% v/v) in AGR showed a significant COD, NH3–N, and PO4–P removal of 62%–65%, 61%–93%, and 56%–64%, respectively. Mass balance analysis indicated that the AGR requires a lower nitrogen percentage for microbial assimilation than the COD and phosphorus. Proteobacteria and Planctomycetes were identified as the predominant (80%) bacterial community in aerobic granules responsible for removing COD, NH3–N, and PO4–P from leachate using AGR. The maximum biodegradation rate (rmax) and half-saturation constant (Ks) of COD in AGR were determined as 123.5 mg/L h and 309 mg/L, respectively.