Increasing the capacity of an extended nutrient removal plant by using different techniques

Abstract

A comprehensive investigation which included full scale tests was initiated towards the late 1980:s with the primary aim to find an appropriate technology for the Klagshamn wastewater treatment plant in Malmö, Sweden. The finally selected strategy enabled that a concentration of less than 8 mg N/l could be reached in the secondary effluent without having to extend either the primary or secondary treatment step at the actual load on the plant. In order to comply with a future stringent phosphorus standard however, a tertiary filtration plant has to be built. In future, it has to be anticipated that the load on the plant may be doubled due to the fact that a bridge between Malmö and Copenhagen is being built. As a consequence, it was important to continue the upgrading work by estimating the ultimate plant capacity and to look for measures to increase the capacity if necessary. By optimising the plant operation, it seems possible to reach an effluent nitrogen concentration of less than 12 mg/l at a load corresponding to the future design load. The suggested approach implies that the plant has to be operated on the margin and as a consequence the possibility to include a denitrification step as part of the filtration plant was also investigated. As a result, it was decided to build a separate denitrification step at the same time as the filtration plant was built.