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Hägele FA, Dörner R, Koop J, Lübken M, Seidel U, Rimbach G, Müller MJ, Bosy-Westphal A. Impact of one-day fasting, ketogenic diet or exogenous ketones on control of energy balance in healthy participants. Clin Nutr ESPEN 2023; 55:292-299. [PMID: 37202059 DOI: 10.1016/j.clnesp.2023.03.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 03/02/2023] [Accepted: 03/23/2023] [Indexed: 05/20/2023]
Abstract
BACKGROUND & AIMS Oral ketone supplements may mimic the beneficial effects of endogenous ketones on energy metabolism as β-hydroxybutyrate has been proposed to increase energy expenditure and improve body weight regulation. Therefore, our objective was to compare the effects of a one-day isocaloric ketogenic diet, fasting and supplementation with ketone salts on energy expenditure and appetite perception. METHODS Eight healthy young adults (4 women, 4 men, age 24 ± 3 years, BMI 24.3 ± 3.1 kg/m2) participated in a randomized cross-over trial with four 24 h-interventions in a whole room indirect calorimeter at a physical activity level of 1.65: (i) total fasting (FAST), (ii) isocaloric ketogenic diet (3.1% energy from carbohydrates (CHO), KETO), (iii) isocaloric control diet (47.4% energy from CHO, ISO), and (iv) ISO supplemented with 38.7 g/d ketone salts (exogenous ketones, EXO). Effects on serum ketone levels (15 h-iAUC), energy metabolism (total energy expenditure, TEE; sleeping energy expenditure, SEE; macronutrient oxidation) and subjective appetite were measured. RESULTS Compared to ISO, ketone levels were considerably higher with FAST and KETO and little higher with EXO (all p > 0.05). Total and sleeping energy expenditure did not differ between ISO, FAST and EXO whereas KETO increased TEE (+110 ± 54 kcal/d vs. ISO, p < 0.05) and SEE (+201 ± 90 kcal/d vs. ISO, p < 0.05). CHO oxidation was slightly decreased with EXO compared to ISO (-48 ± 27 g/d, p < 0.05) resulting in a positive CHO balance (p < 0.05). No differences between the interventions were found for subjective appetite ratings (all p > 0.05). CONCLUSION A 24 h-ketogenic diet may contribute to maintain a neutral energy balance by increasing energy expenditure. Exogenous ketones in addition to an isocaloric diet did not improve regulation of energy balance. CLINICAL TRIAL REGISTRATION NCT04490226 https://clinicaltrials.gov/.
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Affiliation(s)
- Franziska A Hägele
- Department of Human Nutrition, Institute of Human Nutrition and Food Sciences, Kiel University, Düsternbrooker Weg 17, 24105 Kiel, Germany
| | - Rebecca Dörner
- Department of Human Nutrition, Institute of Human Nutrition and Food Sciences, Kiel University, Düsternbrooker Weg 17, 24105 Kiel, Germany
| | - Jana Koop
- Department of Human Nutrition, Institute of Human Nutrition and Food Sciences, Kiel University, Düsternbrooker Weg 17, 24105 Kiel, Germany
| | - Marie Lübken
- Department of Human Nutrition, Institute of Human Nutrition and Food Sciences, Kiel University, Düsternbrooker Weg 17, 24105 Kiel, Germany
| | - Ulrike Seidel
- Department of Food Sciences, Institute of Human Nutrition and Food Sciences, Kiel University, Hermann-Rodewald-Strasse 6, 24098 Kiel, Germany
| | - Gerald Rimbach
- Department of Food Sciences, Institute of Human Nutrition and Food Sciences, Kiel University, Hermann-Rodewald-Strasse 6, 24098 Kiel, Germany
| | - Manfred J Müller
- Department of Human Nutrition, Institute of Human Nutrition and Food Sciences, Kiel University, Düsternbrooker Weg 17, 24105 Kiel, Germany
| | - Anja Bosy-Westphal
- Department of Human Nutrition, Institute of Human Nutrition and Food Sciences, Kiel University, Düsternbrooker Weg 17, 24105 Kiel, Germany.
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Gehring T, Deineko E, Hobus I, Kolisch G, Lübken M, Wichern M. Effect of sewage sampling frequency on determination of design parameters for municipal wastewater treatment plants. Water Sci Technol 2021; 84:284-292. [PMID: 34312336 DOI: 10.2166/wst.2020.588] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The uncertainty associated with the determination of load parameters, which is a key step in the design of wastewater treatment plants (WWTPs), was investigated on the basis of data sets from 58 WWTPs. A further analysed aspect was the organic load variations associated with variable sewage temperatures. Data from 26 WWTPs with a high inflow sampling frequency was used to simulate scenarios to investigate the effect of lower sampling frequencies through a Monte Carlo approach. The calculation of 85-percentile values for chemical oxygen demand (COD) loadings based on only 26 samples per year is associated with a variability of up to ±18%. Approximately 90 samples per year will be necessary to reduce this uncertainty for estimation of COD loadings below 10%. Hence, a low sampling frequency can potentially lead to under- or overestimation of design parameters. Through an analogous approach, it was possible to identify uncertainties of ±11% in COD loading when weekly average data was used with four samples per week. Finally, a tendency to lower COD input loads with increasing temperatures was identified, with a reduction of about 1% of the average loading per degree Celsius.
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Affiliation(s)
- T Gehring
- Institute of Urban Water Management and Environmental Engineering, Department of Civil and Environmental Engineering, Ruhr-Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany
| | - E Deineko
- Institute of Urban Water Management and Environmental Engineering, Department of Civil and Environmental Engineering, Ruhr-Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany; German Aerospace Center (DLR), Institute of Transport Research, Commercial Transport, Rudower Chaussee 7, 12489 Berlin, Germany
| | - I Hobus
- Wupperverbandsgesellschaft für integrale Wasserwirtschaft mbH, Untere Lichtenplatzer Str. 100, 42289 Wuppertal, Germany
| | - G Kolisch
- Wupperverbandsgesellschaft für integrale Wasserwirtschaft mbH, Untere Lichtenplatzer Str. 100, 42289 Wuppertal, Germany
| | - M Lübken
- Institute of Urban Water Management and Environmental Engineering, Department of Civil and Environmental Engineering, Ruhr-Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany
| | - M Wichern
- Institute of Urban Water Management and Environmental Engineering, Department of Civil and Environmental Engineering, Ruhr-Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany
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Lübken M, Kosse P, Clausen K, Pehl B, Bendt T, Wichern M. Direct dosage of reactivated carbon from waterworks into the activated sludge tank for removal of organic micropollutants. Water Sci Technol 2018; 2017:370-377. [PMID: 29851389 DOI: 10.2166/wst.2018.154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The thermal reactivation of granular activated carbon is a substantial ecological and economic benefit in the process of drinking water treatment. A significant amount of abraded carbon, which is similar to powdered activated carbon (PAC), is produced that can be brought to application at wastewater treatment plant level for the removal of micropollutants in a powdered activated carbon-activated sludge (PAC-AS) system. This excess carbon derived as a by-product from the reactivation process in a waterworks was applied directly into the activated sludge tank and has been elevated in this study by monitoring the removal efficiencies for benzotriazole, carbamazepine, diclofenac, metoprolol and sulfamethoxazole in the effluent of a semi-technical wastewater treatment plant of 39 m3. A simulation-derived sampling strategy was applied to optimize the recovery rates of the micropollutants. Flow-proportional, 72-hour composite sampling was considered best. The elimination rates obtained for a 10 g PAC·m-3 dosage were 73% for benzotriazole, 59% for carbamazepine, 60% for diclofenac, 67% for metoprolol and 48% for sulfamethoxazole. The obtained results underline the importance of appropriate sampling strategies, which can be derived from hydraulic modeling.
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Affiliation(s)
- M Lübken
- Institute of Urban Water Management and Environmental Engineering, Ruhr-Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany E-mail:
| | - P Kosse
- Institute of Urban Water Management and Environmental Engineering, Ruhr-Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany E-mail:
| | - K Clausen
- Institute of Urban Water Management and Environmental Engineering, Ruhr-Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany E-mail:
| | - B Pehl
- Stadtentwässerungsbetrieb Düsseldorf, Auf Dem Draap 15, 40221 Düsseldorf, Germany
| | - T Bendt
- Stadtentwässerungsbetrieb Düsseldorf, Auf Dem Draap 15, 40221 Düsseldorf, Germany
| | - M Wichern
- Institute of Urban Water Management and Environmental Engineering, Ruhr-Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany E-mail:
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Azari M, Le AV, Lübken M, Denecke M. Model-based analysis of microbial consortia and microbial products in an anammox biofilm reactor. Water Sci Technol 2018; 77:1951-1959. [PMID: 29676752 DOI: 10.2166/wst.2018.081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
A mathematical model for a granular biofilm reactor for leachate treatment was validated by long-term measured data to investigate the mechanisms and drivers influencing biological nitrogen removal and microbial consortia dynamics. The proposed model, based on Activated Sludge Model (ASM1), included anaerobic ammonium oxidation (anammox), nitrifying and heterotrophic denitrifying bacteria which can attach and grow on granular activated carbon (GAC) particles. Two kinetic descriptions for the model were proposed: with and without soluble microbial products (SMP) and extracellular polymeric substance (EPS). The model accuracy was checked using recorded total inorganic nitrogen concentrations in the effluent and estimated relative abundance of active bacteria using quantitative fluorescence in-situ hybridization (qFISH). Results suggested that the model with EPS kinetics fits better for the relative abundance of anammox bacteria and nitrifying bacteria compared to the model without EPS. The model with EPS and SMP confirms that the growth and existence of heterotrophs in anammox biofilm systems slightly increased due to including the kinetics of SMP production in the model. During the one-year simulation period, the fractions of autotrophs and EPS in the biomass were almost stable but the fraction of heterotrophs decreased which is correlated with the reduction in nitrogen surface loading on the biofilm.
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Affiliation(s)
- M Azari
- Department of Urban Water- and Waste Management, University of Duisburg-Essen, Universitätsstraße 15, 45141 Essen, Germany E-mail: ; Contributed equally to this work
| | - A V Le
- Department of Urban Water- and Waste Management, University of Duisburg-Essen, Universitätsstraße 15, 45141 Essen, Germany E-mail: ; Contributed equally to this work
| | - M Lübken
- Institute of Urban Water Management and Environmental Engineering, Ruhr-Universität Bochum, Universitätsstraβe 150, 44801 Bochum, Germany
| | - M Denecke
- Department of Urban Water- and Waste Management, University of Duisburg-Essen, Universitätsstraße 15, 45141 Essen, Germany E-mail:
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Schmidtlein F, Lübken M, Grote I, Orth H, Wichern M. Photoreactivation and subsequent solar disinfection of Escherichia coli in UV-disinfected municipal wastewater under natural conditions. Water Sci Technol 2015; 71:220-226. [PMID: 25633945 DOI: 10.2166/wst.2014.488] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Photoreactivation of ultraviolet (UV)-disinfected wastewater of different qualities was experimentally assessed. Photoreactivation ability of secondary effluent and microstrained inflow was analyzed in different samples of 50 mL (Petri dish) and 7,000 mL volume to describe open channel effluent situations of wastewater treatment plants in a more realistic approach. The small sample of secondary effluent revealed a total log10 inactivation of 1.8 units and the small sample of microstrained inflow a total log10 inactivation of 3.2, with an applied UV-254 fluence of 84 and 253 J/m², respectively. Maximum net photoreactivation for secondary effluent and microstrained inflow was in the order of 1.2 log10 and 0.37 log10 units, respectively, for both sample sizes. However, significantly faster photoreactivation performance was generally determined for small sample volumes. The photoreactivation processes were completely compensated for by solar disinfection within a 120 min exposure time. Solar disinfection processes were negligible in the larger sample volumes of microstrained inflow. For municipal wastewater treatment systems with open channel effluents, it is essential to take into consideration the dependence of solar UV-365 fluence rate on water depth and wastewater characteristics.
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Affiliation(s)
- F Schmidtlein
- Institute of Urban Water Management and Environmental Engineering, Ruhr-Universität Bochum, Universitätsstraße 150, Bochum 44780, Germany E-mail:
| | - M Lübken
- Institute of Urban Water Management and Environmental Engineering, Ruhr-Universität Bochum, Universitätsstraße 150, Bochum 44780, Germany E-mail:
| | - I Grote
- Institute of Urban Water Management and Environmental Engineering, Ruhr-Universität Bochum, Universitätsstraße 150, Bochum 44780, Germany E-mail:
| | - H Orth
- Institute of Urban Water Management and Environmental Engineering, Ruhr-Universität Bochum, Universitätsstraße 150, Bochum 44780, Germany E-mail:
| | - M Wichern
- Institute of Urban Water Management and Environmental Engineering, Ruhr-Universität Bochum, Universitätsstraße 150, Bochum 44780, Germany E-mail:
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Wichern M, Lübken M, Horn H. Optimizing sequencing batch reactor (SBR) reactor operation for treatment of dairy wastewater with aerobic granular sludge. Water Sci Technol 2008; 58:1199-1206. [PMID: 18845857 DOI: 10.2166/wst.2008.486] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The biological wastewater treatment using aerobic granular sludge is a new and very promising method, which is predominantly used in SBR reactors which have higher volumetric conversion rates than methods with flocculent sludge. With suitable reactor operation, flocculent biomass will accumulate into globular aggregates, due to the creation of increased substrate gradients and high shearing power degrees. In the research project described in this paper dairy wastewater with a high particle load was treated with aerobic granular sludge in an SBR reactor. A dynamic mathematical model was developed describing COD and nitrogen removal as well as typical biofilm processes such as diffusion or substrate limitation in greater detail. The calibrated model was excellently able to reproduce the measuring data despite of strongly varying wastewater composition. In this paper scenario calculations with a calibrated biokinetic model were executed to evaluate the effect of different operation strategies for the granular SBR. Modeling results showed that the granules with an average diameter of 2.5 mm had an aerobic layer in between 65-95 microm. Density of the granules was 40 kgVSS/m3. Results revealed amongst others optimal operation conditions for nitrogen removal with oxygen concentrations below 5 gO2/m3. Lower oxygen concentrations led to thinner aerobic but thicker anoxic granular layers with higher nitrate removal efficiencies. Total SBR-cycle times should be in between 360-480 minutes. Reduction of the cycle time from 480 to 360 minutes with a 50% higher throughput resulted in an increase of peak nitrogen effluent concentrations by 40%. Considering biochemical processes the volumetric loading rate for dairy wastewater should be higher than 4.5 kgCOD/(m3*d). Higher COD input load with a COD-based volumetric loading rate of 9.0 kgCOD/(m3*d) nearly led to complete nitrogen removal. Under different operational conditions average nitrification rates up to 5 gNH/(m3*h) and denitrification rates up to 3.7 gNO/(m3*h) were achieved.
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Affiliation(s)
- M Wichern
- Institute of Water Quality Control, Technical University of Munich, Am Coulombwall, 85748, Garching, Germany.
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Wichern M, Lübken M, Horn H, Schlattmann M, Gronauer A. Investigations and mathematical simulation on decentralized anaerobic treatment of agricultural substrate from livestock farming. Water Sci Technol 2008; 58:67-72. [PMID: 18653938 DOI: 10.2166/wst.2008.332] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Anaerobic processes are widely used for treatment of both municipal and industrial wastewater as well as agricultural substrates. In contrast to the aerobic methods, they are frequently more cost-efficient, they have a lower surplus sludge production, and the reactors can be run with higher volumetric loads and thus smaller volumes. In the paper presented both experimental data and the application of the Anaerobic Digestion Model No. 1 for agricultural substrate from livestock farming will be described. A 3,500 L reactor with mesophilic operation and loaded with cattle manure was examined with respect to its COD degradation, gas production, and gas composition. Results revealed a reduction of 30-35% COD and a biogas production of 287 L(Biogas)/kg(VS) when operated with a specific loading rate of 3.6 kg(VS)/(m(3).d).After calibration of the ADM 1, which was based predominantly on the acetate uptake rate (k(ac.m)=3.6 g/(g.d)), the disintegration constant (k(Dis)=0.05 d(-1)) and the exact determination of the influent COD fractions contained in the agricultural substrate, it was possible to simulate the measured data of the plant in excellent quality. For future application of the ADM 1 as part of control strategies a sensitivity analysis was carried out. The analysis based on the SVM slope technique has been done to identify highly sensitive biochemical parameters. These are, amongst others, the acetate uptake rate, the disintegration constant, the biomass decay rates and the half saturation constant for ammonia inhibition. Sensitivity analysis of the inflow COD fractions (proteins, carbohydrates, lipids and inert) showed the necessity of detailed measurements for the prediction of the gas flow and composition as well as for prognosis of inhibitions in the anaerobic process. For cattle manure especially the fractions of inert material and carbohydrates should be observed carefully. Due to the high content of NH(4)-N in manure the protein fraction is not as sensitive as the two mentioned above.
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Affiliation(s)
- M Wichern
- Institute of Water Quality Control, Technische Universität München, Am Coulombwall, Garching, Germany.
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Lübken M, Wichern M, Letsiou I, Kehl O, Bischof F, Horn H. Thermophilic anaerobic digestion in compact systems: investigations by modern microbiological techniques and mathematical simulation. Water Sci Technol 2007; 56:19-28. [PMID: 18048973 DOI: 10.2166/wst.2007.729] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Thermophilic anaerobic digestion in compact systems can be an economical and ecological reasonable decentralised process technique, especially for rural areas. Thermophilic process conditions are important for a sufficient removal of pathogens. The high energy demand, however, can make such systems unfavourable in terms of energy costs. This is the case when low concentrated wastewater is treated or the system is operated at low ambient temperatures. In this paper we present experimental results of a compact thermophilic anaerobic system obtained with fluorescent in situ hybridisation (FISH) analysis and mathematical simulation. The system was operated with faecal sludge for a period of 135 days and with a model substrate consisting of forage and cellulose for a period of 60 days. The change in the microbial community due to the two different substrates treated could be well observed by the FISH analysis. The Anaerobic Digestion Model no. 1 (ADM1) was used to evaluate system performance at different temperature conditions. The model was extended to contribute to decreased methanogenic activity at lower temperatures and was used to calculate energy production. A model was developed to calculate the major parts of energy consumed by the digester itself at different temperature conditions. It was demonstrated by the simulation study that a reduction of the process temperature can lead to higher net energy yield. The simulation study additionally showed that the effect of temperature on the energy yield is higher when a substrate is treated with high protein content.
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Affiliation(s)
- M Lübken
- Institute of Water Quality Control, Technical University of Munich, Am Coulombwall, Garching, Germany.
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Lübken M, Wichern M, Bischof F, Prechtl S, Horn H. Development of an empirical mathematical model for describing and optimizing the hygiene potential of a thermophilic anaerobic bioreactor treating faeces. Water Sci Technol 2007; 55:95-102. [PMID: 17506425 DOI: 10.2166/wst.2007.132] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Poor sanitation and insufficient disposal of sewage and faeces are primarily responsible for water associated health problems in developing countries. Domestic sewage and faeces are prevalently discharged into surface waters which are used by the inhabitants as a source for drinking water. This paper presents a decentralized anaerobic process technique for handling of such domestic organic waste. Such an efficient and compact system for treating faeces and food waste may be of great benefit for developing countries. Besides a stable biogas production for energy generation, the reduction of bacterial pathogens is of particular importance. In our research we investigated the removal capacity of the reactor concerning pathogens, which has been operated under thermophilic conditions. Faecal coliforms and intestinal enterococci have been detected as indicator organisms for bacterial pathogens. By the multiple regression analysis technique an empirical mathematical model has been developed. The model shows a high correlation between removal efficiency and both, hydraulic retention time (HRT) and temperature. By this model an optimized HRT for defined bacterial pathogens effluent standards can be easily calculated. Thus, hygiene potential can be evaluated along with economic aspects. In this paper not only results for describing the hygiene potential of a thermophilic anaerobic bioreactor are presented, but also an exemplary method to draw the right conclusions out of biological tests with the aid of mathematical tools.
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Affiliation(s)
- M Lübken
- Institute of Water Quality Control, Technical University of Munich, Am Coulombwall, 85748 Garching, Germany.
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Wichern M, Lübken M, Blömer R, Rosenwinkel KH. Efficiency of the Activated Sludge Model no. 3 for German wastewater on six different WWTPs. Water Sci Technol 2003; 47:211-218. [PMID: 12906292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
In 1999, the Activated Sludge Model No. 3 by the IWA Task Group on Mathematical Modelling for the Design and Operation of Biological Wastewater Treatment was presented. The model is used for the simulation of nitrogen removal. The simulations in this paper were done on the basis of a new calibration of the ASM 3 by Koch et al., with the easily degradable COD measured by respiration. For modelling of EBPR the BioP-Module of Rieger et al., was used. Six German wastewater treatment plants were simulated during this research to test the existing set of parameters of the models on various large scale plants. It was shown that changes for nitrification and enhanced biological phosphorus removal in the set of biological parameters were necessary. Sensible parameters and recommended values are presented in this article. Apart from the values of the changed biological parameters, we will in our examination discuss the modelling of the different activated sludge systems and the influent fractioning of the COD. Two plants with simultaneous denitrification in the recirculation ditch (EBPR) are simulated, one with preliminary dentrification, one with intermittent denitrification (EBPR), one with cascade denitrification (EBPR), and one pilot plant according to the Johannesburg-process (EBPR) which was simulated over a period of three months.
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Affiliation(s)
- M Wichern
- Institute of Sanitary Engineering and Waste Management, University of Hanover (ISAH), Welfengarten 1, 30167 Hannover, Germany.
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