Phosphate uptake and release rates with different carbon sources in biological nutrient removal using a SBR

A three-step sequencing batch reactor (SBR) was used for nutrient removal from synthetic wastewater with different glucose–organic acid mixtures (1/1). Acetic, butyric, propionic and citric acids were used as organic acids along with glucose. The operation consisted of anaerobic, anoxic and oxic (An/Ax/Ox) phases with durations of 2/1/4.5 h. Sludge age was kept constant for 10 days. Phosphate release and uptake rates were determined for different glucose–organic acid mixtures in the feed wastewater. Maximum phosphate uptake (8.1 mg P l−1 h−1) and release rates (2.23 mg P l−1 h−1) were obtained with the glucose–citric acid mixture. The highest (96%) percent phosphate removal at the end of the nutrient removal cycle (7.5 h) was also obtained with the glucose–citric acid mixture while the glucose–acetic acid mixture resulted in comparable percent phosphate removal (95%).