SRT contributes significantly to sludge reduction in the OSA-based activated sludge process.Though activated sludge systems have contributed significantly to the control of hygiene of our society, the wastewater treatment generates large amount of excess sludge.  Sludge retention time (SRT) was the main 'contributor' to sludge reduction.  The sludge reduction percentage of the process with side hydrolysis and acidification was 42%, with the contribution by long SRT of 33%, energy uncoupling of 7.7%, and hydrolysis/acidification of 1.1%. 
SRT
SRT contributes significantly to sludge reduction in the OSA-based activated sludge process.Though activated sludge systems have contributed significantly to the control of hygiene of our society, the wastewater treatment generates large amount of excess sludge. 
OSA-based activated sludge process
Four conditions were examined to clarify the sludge reduction mechanism in the OSA-based process.  In addition, the sludge reduction in the OSA-based process had no obvious impact on the efficiency of nutrient removal.  The clarified mechanism for sludge reduction in the OSA-based process could provide valuable clue for future system optimization.
OSA-based process
Four conditions were examined to clarify the sludge reduction mechanism in the OSA-based process.  In addition, the sludge reduction in the OSA-based process had no obvious impact on the efficiency of nutrient removal.  The clarified mechanism for sludge reduction in the OSA-based process could provide valuable clue for future system optimization.
OSA-based process
Four conditions were examined to clarify the sludge reduction mechanism in the OSA-based process.  In addition, the sludge reduction in the OSA-based process had no obvious impact on the efficiency of nutrient removal.  The clarified mechanism for sludge reduction in the OSA-based process could provide valuable clue for future system optimization.
OSA-based process