Biomedical subjects

S Kunst

Publications and source records attributed to S Kunst.

11 recordsLinked to original sources

PubMed2005

Processes in vertical-flow reed beds: nitrification, oxygen transfer and soil clogging.

Vertical-flow reed beds (VF) with intermittent feeding are extremely reliable regarding aerobic processes. For a save operation with high nitrification rates and without soil clogging it is essential to preserve aerobic conditions in the filter. The challenge is to keep aerobic conditions in the filter without oversizing the system (economical aspects). It is very difficult to determine the current oxygen content in the filters because it ultimately results from complex interactions of a large number of different influencing parameters such as loading rate, degree of clogging, temperature, and hydraulic behaviour of the reed bed. To gain better knowledge of this complex system, different tests and examinations were carried out over several years. Focusing on the questions of identification and the description of conversion and transport processes (water/gas), a full-scale treatment plant under clogged and non-clogged conditions was investigated in detail. Additionally soil column test were carried out. The results make it possible to describe some of the processes and their interactions in the filter body. Recommendations for a safe and controlled operation can be derived.

Bacteria, Aerobic↗

PubMed2004

Start up of deammonification process in one single SBR system.

A process for autotrophic nitrogen removal named aerobic/anoxic deammonification wherein NH4+ is oxidized by nearly 50% to NO2- and subsequently the ammonia is converted together with the nitrite to molecular nitrogen (N2 gas), has come to full-scale application within the last few years. In this research, sludge from a biological rotation disk located at a landfill leachate plant at Mechernich, Germany, which is capable of performing the deammonification process, was used as seed sludge for acclimating deammonification activities in laboratory scale batch-reactors. In parallel, the same tests were performed with normal activated sludge. Research results indicated that deammonification activities could be obtained from the seeded reactor and also, with limited performance, from normal activated sludge in a single SBR system after several months acclimation. It was also seen that oxygen is an important factor that influences the deammonification from both the acclimatization process and process running. Further results were approved that report an impact of nitrite as a process intermediate on the closely related process of anaerobic ammonia oxidation ("Anammox"). However, limiting concentrations on a bacteria population performing deammonification were found to be different to those reported for a pure Anammox-culture. Also the influence of another intermediate, hydrazine, was tested for speeding up the acclimating process by inducing the deammonification activities and recovering the activities of deammonification from nitrite inhibition.

Bacteria, Anaerobic↗

PubMed2004

Model-based evaluation on the conversion ratio of ammonium to nitrite in a nitritation process for ammonium-rich wastewater treatment.

Modeling for nitritation process was discussed and analyzed quantitatively for the factors that influence nitrite accumulation. The results indicated that pH, inorganic carbon source and Hydraulic Retention Time (HRT) as well as biomass concentration are the main factors that influenced the conversion ratio of ammonium to nitrite. A constant high pH can lead to a high nitritation rate and results in high conversion ratio on condition that free ammonia inhibition do not happen. In a CSTR system, without pH control, this conversion ratio can be monitored by pH variation in the reactor. The pH goes down far from the inlet level means a strongly nitrite accumulation. High concentration of alkalinity can promoted the conversion ratio by means of accelerating the nitritation rate through providing sufficient inorganic carbon source(carbon dioxide). When inorganic carbon source was depleted, the nitritation process stopped. HRT adjustment could be an efficient way to make the nitritation system run more flexible, which to some extent can meet the requirements of the fluctuant of inlet parameters such as ammonium concentration, pH, and temperature and so on. Biomass concentration is the key point, especially for a CSTR system in steady state, which was normally circumscribed by the characteristics of bacteria and may also affected by aeration mode and can be increased by prolonging the HRT on the condition of no nitrate accumulation when no recirculation available. The higher the biomass concentration is, the better the nitrite accumulation can be obtained.

Biomass↗

PubMed2003

Nutrient removal from piggery effluent using vertical flow constructed wetlands in southern Brazil.

Santa Catarina State, southern Brazil, has the greatest swine breeding activities of Latin America. Generally, the piggery wastewater is treated in pond systems that are able to remove organic material according to local environmental legislation. However, these systems do not remove nitrogen and phosphorus efficiently. This work deals with a post-treatment system, using vertical flow constructed wetlands. The experiment was conducted in a swine production farm which has 45,000 animals. Although the pond system was able to partially remove the content of nutrients, their concentration in the effluent was high for environmental disposal. A four-bed vertical flow constructed wetland pilot plant, using Typha spp., was built. The pilot plant operated for 280 days for beds 2-4 (sand 2). However, the experiments with beds 1-3 (sand 1) were stopped after 111 days of operation, when a reduction in the wastewater drainage was observed. The beds with sand 2 showed a 33% COD removal, and about 49% of nitrification was observed from 111 days until the end of the operation. PO(4)-P removal was 45% with a loading rate of around 1.36 g m(-2) d(-1).

Animals↗

PubMed2003

Controlling a combined lagoon/reed bed system using the oxidation-reduction potential (ORP).

Lagoon systems achieve good and stable effluent data in regard to organic pollutants, but they charge the receiving waters with relatively high ammonium loads. Therefore an existing lagoon-plant was extended by a vertical flow reed-bed for the special purpose of nitrification. This paper presents the efficiency of the combination plant as well as the possibility to monitor and control the reed-bed operation by the oxidation-reduction potential (ORP). The results show that the combination plant achieved excellent purification results, the average efficiency degrees were 97% for COD, 77% for N(total) and 94% for the TKN elimination. The ORP in the effluent of the reed bed showed a clear dependence in its characteristic course and its absolute values on the current nitrification performance, the oxygen supply and the hydraulic behaviour of the reed bed. Therefore the ORP is a very good indicator for the state of the reed bed, which ultimately results from the accumulation of a large number of different influencing parameters. As the preservation of aerobic conditions in the reed bed is the crucial prerequisite for a high nitrification performance and for the avoidance of clogging, the ORP thus offers the possibility of immediate operation control.

Ecosystem↗

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↗

PubMed2002

Control of bulking sludge caused by Type 021 N and Type 0961 in an industrial wastewater treatment plant with an aerobic selector.

Over a period of 6 months, pilot plant investigations were carried out with the purpose of bulking sludge control with different aerobic selectors. The wastewater was dominated by industrial dischargers, containing volatile fatty acids up to 450 mg/l. With complete-mix-selectors it was not possible to achieve a stable SVI below 150 ml/g. The bulking sludge could only be controlled with a sectionalized selector (HRT 5-8 minutes per section). The SVI decreased to values below 100 ml/g. Shock-loads and increased VFA-concentrations (by dosing NaC2H3OO) did not cause filamentous growth.

Bacteria, Aerobic↗

PubMed2002

Balancing of nitrogen conversion in deammonifying biofilms through batch tests and GC/MS.

Growth carriers from a technical deammonifying moving-bed WWTP were used in batch tests to determine possible N-conversion reactions under varying oxygen and substrate conditions. Deammonification, denitrification, and nitrification reactions could be proved using conventional analysis, combined with gas chromatography/mass spectrometry analysis to get additional information about 15N-isotope labelled gaseous end products of the different reactions. In this orientating study N2O could be observed in some cases up to 12% of the total gas production. N2O production came from incomplete denitrification processes under anoxic or oxygen-limiting conditions and in the absence of organic substrate, as if structural components of deammonifying biofilms play a crucial role for the portion of side-reactions, leading to undesirable gaseous end products.

Ammonia↗

PubMed2002

Nitrification in reed beds--capacity and potential control methods.

Vertical-flow reed beds (VFBs) are known to be very effective regarding nitrification. However, a generally accepted design formula for dimensioning reed beds for a controlled nitrification process has still not been found. Especially for the purpose of nitrification a vertical-flow reed bed (VFB) has been installed following an existing unaerated pond-system. The paper presents the results concerning the limits of the VFB's performance as well as the main factors influencing the nitrification process gained by balancing the conversion rates under different loads. Even under high loads the VFB provides an excellent nitrification performance, which is mainly influenced by the wastewater temperature. The ammonia oxidation rate is about 90% at temperatures over 10 degrees C; at temperatures below 5 degrees C the average nitrification rate is still approximately 50%. The hydraulic load and the TKN load have almost no impact on this efficiency (the maximum load has been: 180 mm/d, 7.1 g TKN/(m2 x d)). The redox potenial, which is continuously measured in the effluent of the reed bed, proved to be dependent on the current nitrification performance and the oxygen supply of the VFB, and therefore appears to be a suitable control parameter for the operation of VFBs.

Ecosystem↗

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↗