Biomedical subjects

A Hippen

Publications and source records attributed to A Hippen.

3 recordsLinked to original sources

PubMed2002

Deammonification in biofilm systems: population structure and function.

For the development of alternative concepts for the cost effective treatment of wastewaters with high ammonium content and low C/N-ratio, autotrophic consortia of micro-organisms with the ability to convert ammonium directly into N2 are of particular interest. Several full-scale industrial biofilm plants eliminating nitrogen without carbon source for years in a stable process, are suspected for some time to harbor active anaerobic ammonium oxidizers in deeper, oxygen-limited biofilm layers. In order to identify the processes of the single-stage nitrogen elimination (deammonification) in biofilm systems and to allocate them to the responsible micro-organisms, a deammonifying moving-bed pilot plant was investigated in detail. 15N-labelled tracer compounds were used as well as 16S rDNA libraries and in situ identification of dominant organisms. The usage of rRNA-targeted oligonucleotide probes (FISH) was particularly emphasized on the ammonium oxidizers of the beta-subclass of Proteobacteria and on the members of the order Planctomycetales. The combined application of these methods led to a deeper insight into the population structure and function of a deammonifying biofilm.

Biofilms↗

PubMed2001

Single stage biological nitrogen removal by nitritation and anaerobic ammonium oxidation in biofilm systems.

In full scale wastewater treatment plants with at times considerable deficits in the nitrogen balances, it could hitherto not be sufficiently explained which reactions are the cause of the nitrogen losses and which micro-organisms participate in the process. The single stage conversion of ammonium into gaseous end-products--which is henceforth referred to as deammonification--occurs particularly frequently in biofilm systems. In the meantime, one has succeeded to establish the deammonification processes in a continuous flow moving-bed pilot plant. In batch tests with the biofilm covered carriers, it was possible for the first time to examine the nitrogen conversion at the intact biofilm. Depending on the dissolved oxygen (DO) concentration, two autotrophic nitrogen converting reactions in the biofilm could be proven: one nitritation process under aerobic conditions and one anaerobic ammonium oxidation. With the anaerobic ammonium oxidation, ammonium as electron donor was converted with nitrite as electron acceptor. The end-product of this reaction was N2. Ammonium and nitrite did react in a stoichiometrical ratio of 1:1.37, a ratio which has in the very same dimension been described for the ANAMMOX-process (1:1.31 +/- 0.06). Via the oxygen concentration in the surrounding medium, it was possible to control the ratio of nitritation and anaerobic ammonium oxidation in the nitrogen conversion of the biofilm. Both processes were evenly balanced at a DO concentration of 0.7 mg/l, so that it was possible to achieve a direct, almost complete elimination of ammonium without addition of nitrite. One part of the provided ammonium did participate in the nitritation, the other in the anaerobic ammonium oxidation. Through the aerobic ammonium oxidation into nitrite within the outer oxygen supplied layers of the biofilm, the reaction partner was produced for the anaerobic ammonium oxidation within the inner layers of the biofilm.

Bacteria, Anaerobic↗

PubMed2001

Six years' practical experience with aerobic/anoxic deammonification in biofilm systems.

Nitrogen elimination through autotrophic micro-organisms is currently in the focus of research projects on the treatment of wastewater with high nitrogen contents, for instance to be able to develop and fix dimensioning parameters for purposeful application. In fact, several industrial plants have already shown for some years that the steady operation of nitrogen elimination without carbon demand is possible. Due to the low growth rates of the participating micro-organisms, these processes can be found in particular in biofilm systems, which also allow for the simultaneous running of the two basic processes. In the following, we will discuss on the basis of the operation results of industrial and pilot-scale plants the operation stability of the aerobic/anoxic deammonification, and explain which experiences are available in particular for conversion in biofilm systems.

Bacteria, Aerobic↗