The Gdansk - East Wastewater Treatment Plant (WWTP) with its predicted average discharge of 2 m3 s-1 is the largest treatment plant with an outfall pointing into the Gulf of Gdansk. The discharge of only mechanically treated wastes into the final kilometre of the River Wisla gave rise to serious environmental problems in the coastal zone. This paper discusses the situation in 1995 and the possible relocation of the outfall based on hydrodynamic conditions. Numerical modelling has been applied to estimate the area influenced by treated water discharged at a variety of locations. The analysis indicates that the optimum location for the outfall would be approximately 2500 metres offshore.