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- Benazzi, F, et al.
(författare)
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On-line estimation and detection of abnormal substrate concentrations in WWTPs using a software sensor: A benchmark study
- 2007
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Ingår i: Environmental Technology. - 1479-487X. ; 28:8, s. 871-882
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a new approach for on-line monitoring and detection of abnormal readily biodegradable substrate (SS) and slowly biodegradable substrate (XS) concentrations, for example due to input of toxic loads from the sewer, or due to influent substrate shock load, is proposed. Considering that measurements of SS and XS concentrations are not available in real wastewater treatment plants, the SS | XS software sensor can activate an alarm with a response time of about 60 and 90 minutes, respectively, based on the dissolved oxygen measurement. The software sensor implementation is based on an extended Kalman filter observer and disturbances are modelled using fast Fourier transform and spectrum analyses. Three case studies are described. The first one illustrates the fast and accurate convergence of the extended Kalman filter algorithm, which is achieved in less than 2 hours. Furthermore, the difficulties of estimating XS when off-line analysis is not available are depicted, and the SS | XS software sensor performances when no measurements of SS and XS are available are illustrated. Estimation problems related to the death-regeneration concept of the activated sludge model no.1 and possible application of the software sensor in wastewater monitoring are discussed.
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- Comas, J, et al.
(författare)
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Demonstration of a tool for automatic learning and reuse of knowledge in the activated sludge process
- 2006
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 53:4-5, s. 303-311
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Tidskriftsartikel (refereegranskat)abstract
- Wastewater treatment plant operators encounter complex operational problems related to the activated sludge process and usually respond to these by applying their own intuition and by taking advantage of what they have learnt from past experiences of similar problems. However, previous process experiences are not easy to integrate in numerical control, and new tools must be developed to enable re-use of plant operating experience. The aim of this paper is to investigate the usefulness of a case-based reasoning (CBR) approach to apply learning and re-use of knowledge gained during past incidents to confront actual complex problems through the IWA/COST Benchmark protocol. A case study shows that the proposed CBR system achieves a significant improvement of the benchmark plant performance when facing a high-flow event disturbance.
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- Comas, J., et al.
(författare)
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Risk assessment modelling of microbiology-related solids separation problems in activated sludge systems
- 2008
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Ingår i: Environmental Modelling & Software. - : Elsevier BV. - 1364-8152. ; 23:10-11, s. 1250-1261
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a risk assessment model for settling problems of microbiological origin in activated sludge systems (filamentous bulking, foaming and rising sludge). The aim of the model is not to diagnose microbiology-related solids separation problems with absolute certainty but to quantify in dynamic scenarios whether simulated operational procedures and control strategies lead to favourable conditions for them to arise or not. The rationale behind the model (which integrates the mechanisms of standard activated sludge models with empirical knowledge), its implementation in a fuzzy rule-based system and the details of its operation are illustrated in the different sections of the paper. The performance of the risk assessment model is illustrated by evaluating a number of control strategies facing different short-term influent conditions as well as long-term variability using the IWA/COST simulation benchmark. The results demonstrate that some control strategies, although performing better regarding operating costs and effluent quality, induce a higher risk for solids separation problems. In view of these results, it is suggested to integrate empirical knowledge into mechanistic models to increase reliability and to allow assessment of potential side-effects when simulating complex processes. (c) 2008 Elsevier Ltd. All rights reserved.
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- Feldman, H., et al.
(författare)
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Assessing the effects of intra-granule precipitation in a full-scale industrial anaerobic digester
- 2019
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 79:7, s. 1327-1337
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a multi-scale model is used to assess the multiple mineral precipitation potential in a full-scale anaerobic granular sludge system. Reactor behaviour is analysed under different operational conditions (addition/no addition of reject water from dewatering of lime-stabilized biomass) and periods of time (short/long term). Model predictions suggest that a higher contribution of reject water promotes the risk of intra-granule CaCO3 formation as a result of the increased quantity of calcium arriving with that stream combined with strong pH gradients within the biofilm. The distribution of these precipitates depends on: (i) reactor height; and (ii) granule size. The study also exposes the potential undesirable effects of the long-term addition of reject water (a decrease in energy recovery of 20% over a 100-day period), caused by loss in biomass activity (due to microbial displacement), and the reduced buffer capacity. This demonstrates how both short-term and long-term operational conditions may affect the formation of precipitates within anaerobic granules, and how it may influence methane production and consequently energy recovery.
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