A study on the influence of chemical dosing on biological phosphorus and nitrogen removal was carried out through batch experimental tests by lab-scale and a full-scale wastewater treatment plant (employing a typical anaerobic-anoxic-oxic treatment). Results indicated that the inhibition of aluminum salt on biological phosphorus release and uptake processes is significant, as well as the inhibition of aluminum salt on Ammonia-Oxidizing Bacteria (AOB) is dominantly observed in the nitrification process and is recoverability. The inhibition of iron salt in biological phosphorus and nitrogen removal is weak, and only the inhibition of iron salt on phosphorus release at anaerobic periods emerge under large dosing. Evidence shows persistent inhibition from the accumulation of chemical doses in sludge mass. Intermittent chemical dosing proves recommendable for simultaneous chemical phosphorus removal. (C) 2010 Elsevier Ltd. All rights reserved.