Aerobic Granule Sludge's Performance In Two Different Reactors

This study mainly focused on the effect of reactor type on the cultivation, morphology, removal efficiency, stability of aerobic granules and membrane fouling. Two systems were used in this study, i.e., SBAR(Sequencing Batch Airlift Reactor) and AGMBR(Aerobic Granule Membrane Bioreactor).In order to confirm the optimal conditions for cultivation of aerobic granule, the effects of settling time, hydraulic retention time, and carbon source on the formation, morphology, performance, and stability of aerobic granules were investigated in SBAR. Results showed that aerobic granule favored to be cultivated under settling time less than 5 min, aeration intensity between 0.15-0.24 m³/h, and hydraulic retention time less than 10 h. Aerobic granule showed different characteristics when fed with different carbon source. Sucrose-fed aerobic granule weas easily formed due to the presence of a large amount of filamentous, they exhibited irregular structure and poor stability. Acetate-fed aerobic granule was relative stable, though they were small and coexisted with flocs. They also showed the highest COD removal efficiency and the lowest TN removal efficiency. Glucose-fed aerobic granule was the most stable ones and their surface was smooth and mainly consisted of bacillus and coccus. The removal efficiency of COD, ammonia-nitrogen, and TN, reached higher than 85%, 88%, and 80%, respectively. The start-up of ethanol-fed aerobic granular reactor needed about 25 days and granules were unstable.The feasibly of treating beer wastewater by aerobic granule was also investigated in SBAR. After aerobic granule was formed and reached steady state by fed with synthesize water, beer wastewater was added gradually and substituted synthesize water eventually. After operated about 3 months, aerobic granules showed excellent ability of adapting moderate beer wastewater. COD, BOD₅, NH₃^--N, TP, and SS in effluent were less than 80,20, 15, 3, 70 mg/L, respectively. The resistance for beer wastewater of aerobic granules was also studied in this study. Results showed that the COD removal efficiency was high than 95% under OLR between 8-16 kg COD/m³Â·d, while they dropped significantly when OLR reached 18kgCOD/m³Â·d.In this study, aerobic granules membrane bioreactors (AGMBR) were built up and the short-term membrane fouling was investigated systematically. Two identical MBRs were operated in parallel with aerobic granules and activated sludge to compare their impacts on membrane fouling. The results showed that aerobic granules have some advantages over conventional bioflocs on controlling membrane fouling. Membrane resistance was mainly evaluated by intrinsic membrane resistance, cake resistance and pore blocking resistance. These results of fouling mechanisms and experiment data suggested that pore blocking resistance was the predominant factor affecting membrane fouling in AGMBR during membrane filtration of sludge suspension, whereas, cake resistance was the predominant factors affecting membrane fouling strongly in activated sludge system. The formation mechanism of membrane foulants was also analyzed by Fourier transform infrared (FITR), the results showed that the proteins and carbonhydrates were significant contributors to membrane foulants.The identical external membrane bioreactor and submerged membrane bioreactor were operated to specify the ability to remove nutrient substrate, the membrane fouling mechanism and the stability of aerobic granules. The results indicated that AGMBR was an excellent biotechnology for handling industrial and municipal wastewater. The COD, NH₃^--N, total nitrogen (TN) removal could reach more than 96%, 90% and 85 %, respectively. In the submerged membrane bioreactor, 2 days after the member module applied, the aerobic granules began to be disaggregated to conventional bioflocs and the physical characteristic was changed dramatically. After 6 days, the aerobic granules was completely disaggregated and led to severe membrane fouling. The value of TMP was over 30 Kpa in 2 days. However, the aerobic granules in external membrane bioreactor were not changed obviously besides the increased granules size. The results suggested that the aerobic granules in R2 had a good behavior and had a positive effect on membrane permeation.