In this study an anaerobic/aerobic sequencing batch reactor was used for an enhanced biological phosphorus removal. These conditions were tested by a laboratory scale reactor (14 liter) with a synthetic feed, glucose being the sole carbon source. However, enhanced biological phosphorus removal (EBPR) was not achieved during this study. A series of batch tests were conducted with various substrates; acetic acid, glucose and the mixture of acetic acid and glucose. High phosphate removal was obtained when acetate was the substrate (68.7%). It was observed that when the acetic acid was used as a sole substrate, the bacteria growing in the alternating anaerobic/aerobic system removed the organic substrate under anaerobic conditions. However, in case of the glucose feed most of the COD removal took place under not truly anaerobic conditions. This also coincides with low phosphate removal (37.8%). These results are in consistent with the results of the continuous operation. When the acetic acid-glucose mixture was used, the phosphate removal decreased down to 60.8%. This was thought to be due to the glucose that reduced the dependency on poly-P as an energy source.