Das Projekt "Study of the influence of long starvation periods on the nitrifying bacteria in SFBBRs" wird vom Umweltbundesamt gefördert und von Universität Magdeburg, Institut für Apparate- und Umwelttechnik, Professur für Umweltschutztechnik durchgeführt. Introduction Smaller wastewater treatment plants may have to experience starvation periods lasting several months. Examples are plants operating on wastewater generated in a tourist area or wastewater from an agricultural crop processing plant operating only seasonally. The nitrifying biofilm develops only slowly over months at temperatures below 20 C. In order to achieve a quick start-up of the nitrification in the next season it is of importance to preserve the nitrifying biofilm during starvation periods as active as possible. Decay process is a general term with distinct meanings depending on the context. From a microbiological point of view, decay implies maintenance, endogenous respiration, degradation of enzymes or lysis due to adverse environmental conditions. In the maintenance process, an external substrate is used to keep the current biological activity going, but the amount of bacteria is not altered. The endogenous respiration concept involves the consumption of the cell-internal substrate, which leads to a loss of activity and slightly reduced biomass. Similarly, enzyme degradation causes a loss of activity, but this is rapidly restored if substrate becomes available. In contrast to the previous processes, lysis leads to death and breaking apart of the cells and therefore to a loss of bacteria. From an engineering process point of view, decay describes the loss of microbial activity in general. Description of the proposed Experimental Work The main goal of this study is to find the best operation conditions for preserving nitrifying bacteria during long starvation periods. Batch experiments are suggested to be carried out weekly to investigate the activity and decay rates change of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in SFBBRs. The initial suggested study period is 4 months. It is believed that long starvation period will harmfully affect the activity of nitrifying bacteria. Therefore actions may be taken in order to keep on the total biomass or regenerate the loss. These actions such as adding external rich ammonia substrate and applying long aeration periods are supposed to be taken. Through this study period the activity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) will be investigated.