Kinetic start-up performance of two large treatment plants for nutrient removal

In 1987 an action plan was passed in the Danish Parliament demanding a considerable reduction of the discharge of nutrients to the aquatic environment in Denmark. Consequently, the two largest wastewater treatment plants in the Copenhagen area had to be upgraded to include nutrient removal. For more than 8 years an extensive effort has been made to determine an optimum solution for this upgrading from a technical and financial point of view. The work included six years of comprehensive pilot plant investigations with the aim of thoroughly studying and interpreting the kinetics of the processes involved. The investigations revealed valuable information particularly concerning limitations of the nitrification process. Consequently, the investigations contributed to an expectation of no unforeseen problems during the implementation of the upgraded plants. This paper presents the results of the start-up of the two full-scale plants with the main emphasis laid on the kinetic performance in relation to the information achieved from the pilot tests. The results showed that the start-up of the full scale plants proceeded with great accuracy as expected from the investigations. Accordingly, the implementation of the plants was carried out successfully, ending an era of more than 10 years in total.