Nutrient Removal in a 2-Stage Biological Sewage Treatment Plant
The Dradenau sewage treatment plant consists basically of a large activated sludge plant which supplements the treatment stages of the Köhlbrandhöft plant. Although built to mainly oxidize ammonia and despite unfavourable operating conditions - the different locations of the Köhlbrandhöft and Dradenau plants - considerable amounts of nitrogen have successfully been eliminated. Denitrification takes place in the distribution channel of the Dradenau plant and in one of the biological stages of the Köhlbrandhöft plant. This stage takes over the excess sludge from the Dradenau plant resulting in nitrifying - and denitrifying - part of the nitrogen load already here. There is an average overall reduction of 70 %. Simultaneous precipitation at the Köhlbrandhöft treatment plant reduces the phosphorus concentration in the effluent of the combined treatment plants Köhlbrandhöft/Dradenau to values recently set by legal regulations (1 mgP/l).