This study investigates the potential of mechanically disintegrated surplus activated sludge (SAS) to be used as an internal carbon source for biological nutrient removal (BNR) using two laboratory tests. In the phosphorus release test, the addition of disintegrated sludge as a carbon source was able to enhance phosphate (PO4-P) release by 14.9 mg l(-1) PO4-P when compared with acetate (7.9 mg l(-1) PO4-P), considering the 4.3 mg l(-1) PO4-P released in the control vessel, without carbon addition. Similarly, in the denitrification test, the nitrate (NO3-N) consumption rate was improved after the addition of disintegrated sludge (14.9 mg NO3-N g(-1) VSS h(-1)) compared with acetate (7.0 mg NO3-N g(-1) VSS h(-1)), taking in consideration the rate obtained in the control vessel (6.9 mg NO3-N g(-1) VSS h(-1)). Two to five minutes of SAS disintegration time in the deflaker (2300-6200 kJ kg(-1) total solids) is recommended for this application. (c) 2008 Elsevier Ltd. All rights reserved.