【正文】 21). 3. Results and discussion Fig. 1 presents data of MLSS and yield observed during the operational period of the reactor. One of the advantages of MBR reactor was it can be operated in high MLSS concentration. The reactor was seeded with EBPR sludge from the Kiheung, sewage treatment plant, Korea. The reactor was startup with the MLSS concentration of 5700 mg/L. It starts to increase steadily with increase in period of reactor operation and reached a value of 8100 mg/L on day 38. From then onwards, MLSS concentration was maintained in the range of 7500 mg/L by withdrawing excess sludge produced and called run I. The observed yields (Yobs) for experiments without sludge digestion (run I) and with sludge digestion were calculated and given in Fig. 1. The Yobs for run I was found to be gMLSS/gCOD. It was paratively lower than a value of gMLSS/gCOD reported for the conventional activated sludge processes (Tchobanoglous et al., 2021). The difference in observed yield of these two systems is attributed to their working MLSS concentration. At high MLSS concentration the yield observed was found to be low (Visvanathan et al., 2021). As a result of that MBR generated less presently used MLSS ranges (一 g/L) are selected on the basis of the remendation by Rosenberger et al. (2021). In their study, they reported that the general trend of MLSS increase on fouling in municipal applications seems to result in no impact at medium MLSS concentrations (7 一 12 g/L). The thermo chemical sludge digestion was started on day 70 by withdrawing sludge at the ratio of ％ Q/day. The sludge digestion period was divided into two phases namely, run II (day 70139) and run III (day 140210). During run II, the MLSS concentration in MBR was maintained around 7500 mg/L and for run III it was maintained around 10500 mg/L. Both of these two runs (II and III) demonstrate the role of sludge disintegration in controlling the excess sludge production. The Yobs for run II and III were found to be , respectively. It accounts for 58% and 75% of sludge reduction when pared to run I. The observed yield for run III was found to be lower than run II. This is due to the fact that at run III more amount of biosolids were subjected to be sludge digestion. It is evident from the data that the COD removal efficiency of A2O system remains unaffected before and after the introduction of sludge digestion practices. A test analysis showed that the differences between the period without sludge digestion (run I) and with sludge digestion (run II and III) are not statistically significant. However, it has been reported that, in wastewater treatment processes including disintegrationinduced sludge degradation, the effluent water quality is slightly detonated due to the release of nondegradable substances such as soluble microbial products (Yasui and Shibata, 1994。t cause membrane fouling. 4. Conclusions Stable operation of MBR process was possible without significant accumulation of biomass when a part of the biological solids were disintegrated with alkali at pH 11 and temperature 75℃ Thermo chemical sludge digestion favors the recovery of phosphorous in the supernatant using calcium salts. The system can run for a long period of time with any further detoriation in TP removal efficiency. Further studies focusing on fate of disintegrated sludge are in progress. Acknowledgements This work was partly supported by the GS group of panies and Brain Korea 21 program from the Korean Ministry of Education References 1. Akin, ., Ugurlu, A., 2021. The effect of an anoxic zone on biological phosphorus removal by a sequential batch reactor. Bioresour. Technol. 94, 17 2. APHA, 2021. Standard Methods for the Examination of Water and Wastewater, 21 st ed. American Public Health Association, American Water Works Association,Water Pollution and Control Federation, Washington, DC 3. 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