IN-SITU STRUCTURE FUNCTION STUDIES IN WASTE-WATER TREATMENT SYSTEMS/

As an example of the importance and the potential of in situ structure /function studies, nitrifying aggregates from different zones of a lab -scale fluidised bed reactor were analysed by microelectrode measureme nts of O-2, NH4+, NO2-, and NO3- and in situ hybridisation targeting t he 16S rRNA of the nitrifying bacteria. A shift from an ammonia oxidis ing to a nitrite oxidising community is present along the reactor. In the single aggregates an active nitrifying shell of about 100 mu m cou ld be related to the maximum abundance of nitrifiers in this zone. Int erestingly, the main actors in this system are not representatives of the well-described genera Nitrosomonas and Nitrobacter but some other ammonia oxidisers from the beta subclass of Proteobacteria and a thus far unknown nitrite oxidising population. (C) 1998 IAWQ. Published by Elsevier Science Ltd.