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Bioaugmentation by nitrification with return sludge (BABE technology) PhD-student: Ir. Sonia Salem Tel: +31 15 278 1482 e-mail: [email protected] Promotor: Prof. dr.ir. Mark C.M. van Loosdrecht Institute: Delft University of Technology, Department of Biotechnology, Environmental Biotechnology group (EBT) Project term: April 2000 – December 2004 Financed by: DHV Water- STOWA Description The nitrification capacity of an activated sludge process can be augmented by the addition of nitrifiers. These bacteria are usually added as cell suspension. An important disadvantage of adding bacteria in suspension is that they are susceptible to grazing by higher organisms, and not necessarily adapted to the conditions of the actual treatment process. The so-called BABE® (Biological Augmentation Batch Enhanced) technology, developed by DHV in cooperation with the TUD overcomes this problem by producing nitrifying bacteria into the activated sludge flocs. To achieve this, a limited amount of activated sludge from the main process is recycled over the BABE reactor. The concept has two main goals: biological treatment of a nitrogen rich side-stream and augmentation of nitrifying bacteria in the main stream. In this project, the augmentation technology was proposed and experimentally evaluated. First, the effect of feeding a normal activated sludge system with nitrifiers enriched in a separate reactor (the so-called BABE reactor) was studied. A dynamic simulation model was used for evaluating design criteria. A high-load WWTP (Houtrust in Den Haag) and a lowload (Walcheren), partially nitrifying WWTP were taken as examples. The simulations gave proper design criteria and showed the advantages of upgrading according to the BABE concept. The process was tested at full-scale at the WWTP of Garmerwolde (300,000 PE) in the north of the Netherlands. These experiments were successfully conducted by DHV and supported by model-evaluation and FISH analysis at the TU Delft. In the BABE reactor nitrogen from the sludge digestion was converted. Moreover FISH analysis revealed that nitrifying bacteria were being augmented in the main treatment plant, leading to increased nitrification capacity. The simulations have shown that the decay rate of nitrifiers is a crucial factor for designing the BABE reactor. Extensive experimental work was done to evaluate the decay rate of nitrifiers under different conditions and different temperatures. The sludge of Den Bosch WWTP was used for experiments where the first full-scale application of the BABE The BABE reactor in Garmerwolde WWTP process will take place. (300000 p.e.) Project Outcome: New process for augmentation of nitrifiers in sludge: BABE - Salem S, Berends D, Van Loosdrecht MCM & Heijnen JJ. (2003). Bio-augmentation by nitrification with return sludge. Water Res 37(8) p1794-1804. Mathematical modeling of the BABE process - Salem S, Berends D, Van Loosdrecht MCM & Heijnen JJ. (2002). Model based evaluation of a new upgrading concept for N-removal Water Sci Technol 45(6) p169-176. - Berends D.H.J.G., van der Kuij R.J., Salem S., Uiiterlinde C. (2002). BABE-technologie voor volwassen. H2O (in Dutch) 19, 81-83.