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| 2. |
- Jeppsson, Ulf, et al.
(författare)
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Reduced Order Models for On-Line Parameter Identification of the Activated Sludge Process
- 1993
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Ingår i: Water Science and Technology. - 0273-1223. ; 28:11-12, s. 173-183
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Tidskriftsartikel (refereegranskat)abstract
- A reduced order dynamic model for an activated sludge process performing carbonaceous removal, nitrification, and denitrification is proposed. Based on directly measurable real time data - by methods available today - all model parameters are identified on-line. A simplified extended Kalman filter is used for the actual identification. Verification of the results is based on computer simulations of the IAWQ Activated Sludge Model No. 1. The reduced order model presented herein may serve as a tool for predicting the dynamic behaviour of a biological wastewater treatment plant since the parameters under varying operating conditions can be tracked on-line. The model parameters are effectively estimated even when the measurements are affected by a significant level of noise. The model is aimed for operation and control purposes as an integral part of a hierarchical control structure.
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| 3. |
- Lagerkvist, Anders, et al.
(författare)
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Control of two step anaerobic degradation of municipal solid waste (MSW) by enzyme addition
- 1993
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 27:2, s. 47-56
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Tidskriftsartikel (refereegranskat)abstract
- The addition of cellulolytic enzymes to MSW has been tried under methanogenic and acidogenic conditions in 0.1 m3 landfill models. An enhanced degradation seems to follow the enzyme addition in both cases. During acidogenic conditions the observed conversion of cellulose was 42 and 29% respectively, with and without enzyme addition. The enzyme addition did not result in a change from methanogenic to acidogenic conditions. A similar conversion of VS can be achieved during methanogenic and acidogenic conditions; at the completion of this experiment the conversion of VS was in excess of 50% in the methanogenic models and somewhat lower than 40% in the acidogenic models (the latter still yielding strong leachates). The results of some standard waste-water analyses were compared and it is concluded that especially acid leachates may cause analytical problems.
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| 4. |
- Pelkonen, Markku, et al.
(författare)
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New control parameters and measurement techniques for the activated sludge process
- 1993
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 27:5-6, s. 287-295
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Tidskriftsartikel (refereegranskat)abstract
- An on-line oxygen uptake and CO2-production rate measurement system was used to analyse the biomass activity. CO2-production rate corresponded well with oxygen uptake rate in the carbon oxidation process. In the nitrification process the ratio CO2-prod./O2-consumed (r(q)) had a larger variation, but CO2-production had a good correlation with utilized COD; variation of the r(q)-value indicate differences in the auto-/heterotrophic oxidation balance. From this basis the oxygen uptake rate for carbon oxidation and nitrification can be separated. The comparison with two biomass determination methods based on ATP-analysis shows that for heterotrophic biomass the methods indicate clearly different changes of ATP, for nitrification process the results were more compatible. By combining the biomass and on-line measurements with biomass growth model based on IAWPRC-model equations reasonably good estimates were obtained. Best fit of model was in the nitrification process; by using VSS as the measure of biomass the fit was poor. The differences in the ATP-measurement results affect also the model coefficients.An on-line oxygen uptake and CO2-production rate measurement system was used to analyze the biomass activity. CO2-production rate corresponded well with oxygen uptake rate in the carbon oxidation process. In the nitrification process the ratio CO2-prod./O2-consumed (rg) had a larger variation, but CO2-production had a good correlation with utilized COD; variation of rg-value indicate differences in auto-heterotrophic oxidation and nitrification can be separated. The comparison with two biomass determination methods based on ATP-analysis shows that for heterophil biomass the methods indicate clearly different changes of ATP, for nitrification process the results were more compatible. By combining the biomass and on-line measurements with biomass growth model based on IAWPRC-model equations reasonably good estimated were obtained. Best fit of model was in the nitrification process; by using VSS as the measure of biomass the fit was poor. The differences in the ATP-measurement results affect also the model coefficients
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| 5. |
- Pelkonen, Markku
(författare)
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Upgrading oxygen transfer in the activated sludge process
- 1990
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 22:7-8, s. 253-260
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Tidskriftsartikel (refereegranskat)abstract
- The objectives were to get some information on the variation of the alpha factor and to study factors affecting oxygen transfer efficiency in fine-bubble aeration. Results from a 5 week continuous operation of a batch aeration column process show that the variation of the alpha factor was considerable in the aeration basin, especially at the inlet end. The variation follows a diurnal rhythm and the weekly variation is much smaller. The off-gas method was used to examine factors affecting oxygen transfer in process conditions. Regression models were constructed to describe the transfer process both on a semitechnical scale and on a full scale. The most important factors are the specific air flow rate, the respiration rate and the DO concentration. The enhancement in OTE through the respiration rate and the DO concentration is due to a biological mechanism. To optimize the transfer process it is necessary to maintain a high respiration rate and a sufficiently high DO concentration.The objectives were to get some information on the variation of the alpha factor and to study factors affecting oxygen transfer efficiency in finebubble aeration. Results from a 5 week continuous operation of a batch aeration column process show that the variation of the alpha factor was considerable in the aeration basin, especially at the inlet end. The variation follows a diurnal rhythm and the weekly variation is much smaller. The off-gas method was used to examine factors affecting oxygen transfer in process conditions. Regression models were constructed to describe the transfer process both on a semitechnical scale and on a full scale. The most important factors are the specific air flow rate, the respiration rate and the DO concentration. The enhancement in OTE through the respiration rate and the DO concentration is due to a biological mechanism. To optimize the transfer process it is necessary to maintain a high respiration rate and a sufficiently high DO concentration.--------------------------------------------------------------------------------
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| 6. |
- Perrusquía, Gustavo, 1954
(författare)
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An Experimental Study on the Transport of Sediment in Sewer Pipes with a Permanent Deposit
- 1992
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 25:8, s. 115-122
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Tidskriftsartikel (refereegranskat)abstract
- An experimental study of the transport of sediment in a part-full pipe was carried out in a concrete pipe. The experiments were confined to bedload transport. The purpose of this study was to analyze the flow conditions that characterize the stream traction in pipe channels and their relationship to flow resistance and sediment transport rate. Three procedures used in this kind of experimental study were tested and found valid: 1) the vertical velocity distribution near the sediment bed can be described by the velocity-defect law, 2) the side wall elimination procedure can be used to compute the hydraulic radius of the sediment bed, and 3) the critical shear stress of the sediment particles can be obtained by using Shields' diagram. A relationship to estimate bedload transport, based on dimensional analysis, was proposed. This was expressed in terms of both flow and particle parameters as well as geometric factors. Further experimental work is recommended before this relationship can be fully incorporated in a simulation model for the analysis of storm sewers.
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| 7. |
- SZUCS, A, et al.
(författare)
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ANALYSIS OF SAMPLING FREQUENCY IN GROUNDWATER QUALITY MONITORING SYSTEMS - A CASE-STUDY
- 1994
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Ingår i: WATER SCIENCE AND TECHNOLOGY. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0273-1223. ; 30:10, s. 73-78
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Tidskriftsartikel (refereegranskat)abstract
- Sampling frequency is one of the most crucial factors in the design of groundwater quality monitoring systems. Monitoring systems in general have two major objectives: (1) to describe natural processes and long-term changes and (2) to serve as alarm-syste
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