The background of the diploma thesis is the implementation of the IPPC-directive and the adjustment of the waste water treatment of urea and melamine plants to the state of the art. First, the present legal situation in terms of waste water from urea and melamine plants is defined and the implementation of the IPPC-directive in Austria and its future impact on the company is described. Furthermore the state of the art for urea and melamine manufacturing and treatment of their waste water is presented. In the second part of my thesis the present situation concerning water consumption, waste water formation and treatment is shown. For this purpose mass balances were prepared and the composition of the most important streams were analyzed. Based on the conclusions of the former chapters improvement possibilities for the plants are described. These include technical and economic information, e.g. cost saving opportunities. As an overall result of the diploma thesis, possible future emission limits for waste water of the different plants were evaluated and an action plan was presented, that would be needed for reaching these new limits.