An advanced wastewater treatment process involving Sludge reduction, Inorganic solids separation, Phosphorus recovery, and Enhanced nutrient Removal (SIPER) was developed to reduce sludge production, prevent the accumulation of inorganic solids, recover phosphorus, and enhance nutrient removal. The feasibility of recovering carbon (C)-source from excess sludge to enhance nutrient removal and the sludge reduction potential of the process was evaluated. The results showed that sludge hydrolysis and acidification yields were 20 +/- 3% and 34 +/- 2%, respectively. The COD/TN and VFA/TP ratios for the supernatant of alkaline-treated sludge were 2.8 and 2.5 times those in the influent, respectively. Nutrients were removed effectively in the system, especially TN, for which the removal efficiency reached 80 +/- 2%. The C-source recovered from the excess sludge was successfully employed as an internal C-source for enhanced nutrient removal. The observed sludge yield of the system was 0.096 g VSS g COD-1, demonstrating the excellent sludge reduction potential of this process. (C) 2013 Elsevier Ltd. All rights reserved.