Study on rapid formation of aerobic granular sludge promoted by addition of Fe²⁺

The aerobic granular sludge (AGS) process has been regarded as a promising sewage treatment technology. Compared with the activated sludge process, AGS process has the advantages of high efficiency and saving space. However, AGS process has several limitations in its application such as long cultivation cycle and easy disintegration. In this study, Fe²⁺was added to the wastewater to cultivate AGS. The improvement on the cultivation of AGS with the addition of Fe²⁺was investigated by analyzing the characteristics of AGS and the removal efficiency of pollutants. The results showed that adding Fe²⁺(3∼5 mg/L) to the reactor could effectively promote the formation of AGS. The sludge particles could be granulated within 7 days with the average particle size of more than 0.35 mm. In addition, the SEM showed that the dominant microorganisms were coryneform bacteria inside of the AGS. The XRD results indicates that the Fe²⁺was converted into Fe₂O₃presenting in AGS. The mixed liquid suspended solids (MLSS) and the sludge volume index at 30 min (SVI₃₀) was 3.1 g/L and 40 mL/g, respectively, at the 40th day. The COD and NH₄⁺-N were effectively removed by AGS. This study could provide an effective approach for rapid formation of AGS.