Tow plug flow reactors were operated with municipal wastewater according to reversed A2/O process. The only difference was in sludge return ratio. Despite that more VFAs were consumed by denitrification, phosphate removal was enhanced rather than impaired by a higher sludge return ratio of 300%. It seems that higher phosphate removal can be achieved even more nitrate was reduced which means more carbon source consumption. This is contradictory with the well accepted enhanced biological phosphate removal (EBPR) theory, which regards sufficient volatile fatty acids in the wastewater as the indispensable premise. With less phosphate was released in the anaerobic zones, the final phosphate concentration in the effluent was lower when higher sludge return ratio was applied. The results indicated that neither carbon source nor phosphate release can directly determine phosphate uptake ability.