A Bioreactor Designed for Restricting Oversize of Aerobic Granular Sludge

Abstract

Aerobic granular sludge (AGS) with oversized diameter commonly affects its stability and pollutant removal. In order to effectively restrict the particle size of AGS, a sequencing batch reactor (SBR) with a spiny aeration device was put forward. A conventional SBR (R1) and an SBR (R2) with the spiny aeration device treating tannery wastewater were compared in the laboratory. The result indicates that the size of the granular sludge from R2 was smaller than that from R1 with sludge granulation. The spines and air bubbles could effectively restrict the particle size of AGS by collision and abrasion. Nevertheless, there was no significant change in mixed liquor suspended solids (MLSS) and the sludge volume index (SVI) in either bioreactors. The removal (%) of chemical oxygen demand (COD) and ammonia nitrogen (NH4+-N) in these two bioreactors did not differ from each other greatly. The analysis of biological composition displays that the proportion of Proteobacteria decreased slightly in R2. The X-ray fluorescence (XRF) analysis revealed less accumulation of Fe and Ca in smaller granules. Furthermore, a pilot-scale SBR with a spiny aeration device was successfully utilized to restrict the diameter of granules at about 300 μm.

Roles of Granular Sludge Size Restricting and Organic Degradation in an Extended Filamentous AGS System Using Agnail Aeration Device

“…The experimental results demonstrate that the agnail device had no obvious effect on organic degradation through the SND process. This is agreed well with our batch experiment and a previous study [27].…”

“…However, the influent and effluent NH 4 + -N stayed at 25.9-27.1 mg/L and 0 mg/L (Figure 3d). These results indicate that the agnail aeration device can effectively control AGS size, and it had a slight influence on COD removal besides NH 4 + -N. This is consistent with previous work [27].…”

“…This means that the gap between SVI5 and SVI30 was reduced in the extended filamentous bacterial AGS with a large size using the agnail aeration device in this work. These experimental results demonstrate that this agnail device could successfully restrict large AGS [27] and further prevent filamentous overgrowth for long-term operation in this work. The initial MLSS and MLVSS of R1 and R2 were 3543-3573 mg/L and 1613-1633 mg/L, suggesting that the seeding sludge (dewatering sludge) contained about 55% inorganic matter.…”

“…This means that the gap between SVI 5 and SVI 30 was reduced in the extended filamentous bacterial AGS with a large size using the agnail aeration device in this work. These experimental results demonstrate that this agnail device could successfully restrict large AGS [27] and further prevent filamentous overgrowth for long-term operation in this work.…”

“…Concurrently, the organic degradation of COD and NH 4 + -N was successful through the SND process before and after employing the agnail device (Figure 7b-d); the SND efficiency was slightly influenced by the filamentous bacteria existing (Figure 7c), and it recovered after the biomass gradually increased with AGS system recovery (Figure 7d). This indicated that employing the agnail device had no significant negative role in organic degradation [27].…”