(GB2351284-A)   NOVELTY - Waste water treatment comprises passing the water through an anaerobic zone (1), an aerobic zone (3) and a settlement zone (4) and passing the resultant activated sludge to the anaerobic zone. Some or all of the sludge is treated to release intracellular carbon and the sludge is denitrified.    USE - For the treatment of waste water (claimed), especially for the removal of phosphorus.    ADVANTAGE - The need for an aerobic recycle is eliminated. Release of intracellular carbon from the return activated sludge (RAS) acts as a carbon source for denitrifying bacteria and enables the bacteria to denitrify the RAS prior to its entry into the anaerobic zone. In the anaerobic zone, phosphorus-accumulating bacteria can remove phosphorus without competition for available carbon from the denitrifying bacteria. High denitrification rates (e.g. 3-5 mgN/gMLSS/hr) are obtained. Existing plants can easily be modified to carry out this process by installation of a small ultrasound generator, an in-line horn and a small pre-anaerobic tank.    (GB2351284-B)   NOVELTY - Waste water treatment comprises passing the water through an anaerobic zone (1), an aerobic zone (3) and a settlement zone (4) and passing the resultant activated sludge to the anaerobic zone. Some or all of the sludge is treated to release intracellular carbon and the sludge is denitrified.    USE - For the treatment of waste water (claimed), especially for the removal of phosphorus.    ADVANTAGE - The need for an aerobic recycle is eliminated. Release of intracellular carbon from the return activated sludge (RAS) acts as a carbon source for denitrifying bacteria and enables the bacteria to denitrify the RAS prior to its entry into the anaerobic zone. In the anaerobic zone, phosphorus-accumulating bacteria can remove phosphorus without competition for available carbon from the denitrifying bacteria. High denitrification rates (e.g. 3-5 mgN/gMLSS/hr) are obtained. Existing plants can easily be modified to carry out this process by installation of a small ultrasound generator, an in-line horn and a small pre-anaerobic tank.