The quality of bio-sludge of the MSBR system was better than that of the SBR system due to the SVI value. The SVI of the MSBR system under organic loading of 1340 g BOD5/m3 d,
or HRT of 3 d was only 97G8.3 ml/g while it was 142G 13.1 ml/g in the SBR system as shown in Tables 5 and 7.