This paper reviews some of the key wastewater composition parameters, which influence the biological removal of phosphate from wastewaters, such as COD content, volatile fatty acid (VFA) content, cation concentration, phosphorus load, pH and food to microorganism ratio. The discussion also focuses on operational parameters affecting successful nutrient removal in wastewater treatment plants, such as temperature, sludge quality, sludge settlement, dissolved oxygen (DO) concentration, anaerobic P-release and secondary P-release. The aim of this review is to compile an updated document for researchers and operators of biological nutrient removal (BNR) systems. In addition, the article will provide a good foundation for readers with no prior knowledge of the process. (C) 2003 Elsevier Ltd. All rights reserved.