Optimisation of Hamburg's wastewater treatment plants--three years of experience with the new concept.

In the end of the year 1999 a new concept for Hamburg's wastewater treatment plants was commissioned to cope with the additional load of 250,000 PE which has been connected to the existing plant serving 1.85 million population equivalents. The new concept consists of an additional tank for the storage of sludge liquor to avoid peak nitrogen concentrations in the effluent of the plant. This solution has been developed within a study assessing a wide range of concepts with costs between initial [see symbol in text] 100 million and the final construction costs of [see symbol in text]1 million. Here the dynamic simulation showed to be a very efficient planning tool. Within the first three years of operation the chosen solution showed to be able to fulfil the requirements. In 2002 the concept has been improved by a few more measures, mainly the equipment of one of the storage tanks as a SAT tank for further cost effective nitrogen removal. For a further improvement of the treatment capacity additional measures are planned to be carried out within the next years.