Relationships between organic loading and zone settling velocity in the activated sludge process

The performance of the activated sludge process is functionally dependent on the settling and compaction properties of the activated sludge. The settling properties of activated sludges vary markedly depending on the presence or absence of filamentous organisms and on the process operating conditions. In this study the process was operated to minimize the presence of filamentous organisms and to investigate the effects of operating process variables, mainly organic loading. It was found that over the range of organic loadings tested, the ZSV increased with organic loading due to the size of the sludge floc which was also directly proportional to the organic loading. The ZSV in aerobically digested sludge was found to decrease with sludge age.