| 1. |
- Carlsson, Bengt, et al.
(författare)
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Analyses of activated sludge processes consisting of a plug-flow reactor and a non-ideal settler
- 2015
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Ingår i: 9th IWA Symposium on Systems Analysis and Integrated Assessment (Watermatex).
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Konferensbidrag (refereegranskat)abstract
- An activated sludge process (ASP) consisting of a plug-flow reactor (PFR) and a non-ideal settler is modelled and analysed. One soluble substrate component and one particulate biomass are assumed. The biomass growth rate is described by a Monod function. The settler model includes hindered settling and compression. A model describing the steady-state behaviour of the ASP is derived which constrains the settler to work with a fixed sludge blanket height in the thickening zone. The model provides new understanding for these types of ASPs and may be used for novel design schemes. The numerical example suggests that the steady-state solutions of the ASP give a one-parameter family ofsolutions, where the parameter is the recycle ratio 푟.
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| 2. |
- Chistiakova, Tatiana, et al.
(författare)
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Binary classifiers applied to detect DO sensor faults during washing events
- 2015
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Ingår i: Proc. 2nd IWA Conference on New Developments in IT & Water. - : IWA Publishing.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, several classication techniques are applied for monitoring the status of DO sensors in wastewater treatment plants. In particular, DO sensors during washing events are studied and indication parameters from these events are used. The methods considered are the following: k-Nearest Neighbours, Radial Basis Function and Random Forest classiers. The result shows the comparison and the eligibility of the methods to detect a clogged DO-sensor.
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| 3. |
- Diehl, Stefan, et al.
(författare)
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Steady-state analysis and design of activated sludge processes including compressive settling
- 2015
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Ingår i: 9th IWA Symposium on Systems Analysis and Integrated Assessment (Watermatex).
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Konferensbidrag (refereegranskat)abstract
- A simplified activated sludge process (ASP) with one substrate and one particulate biomasscomponent has been analyzed with respect to its steady states. The ASP consists of a completelystirred biological reactor and a settler. The biomass growths according to the Monod function and the decay rate is constant. In the considered one-dimensional settler model, the biomass undergoes hindered settling and compression according to constitutive functions that can be chosen by the investigator. The dynamic settler model is a nonlinear partial differential equation (PDE), so the steady-state equation is an ordinary differential equation. This is a difficulty in the steady-state analysis of an ASP. The key findings are the following:• By analyzing the model PDE, a simple algebraic equation has been obtained that captures the necessary information related to the limiting flux of a settler in steady state in normal operation with a sludge blanket in the thickening zone. The equation relates the recycle concentration to the bulk velocity in the thickening zone with the sludge blanket kept at a specified level.• All steady states of an ASP working in normal operation are given as a one-parameter family of solutions where the parameter is the recycle ratio 푟. Numerical solutions show that the effluent substrate concentration 푆∗ is reduced significantly already for small 푟 and is a decreasing function for all 푟 > 0. The sludge age 휃 can be expressed as an explicit decreasing function of푆∗.• A control curve 푤 = 푤(푟), relating the wastage ratio 푤 to the recycle ratio 푟, gives the possible values that yield the desired steady state with the sludge blanket kept at a specified level.• For given inputs (substrate concentration 푆 in and volumetric flow 푄) to the ASP, a procedure is suggested for the design of an ASP that is constrained to work in normal operation. The procedure gives support in the decision on how to balance the building or start-up costs (which increase with the total area) and operational costs (which increase with 푟 – energy for pumping water).
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| 6. |
- Nájera, Silvano, et al.
(författare)
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ATAD control goals through the analysis of process variables and evaluation of quality, production and cost
- 2015
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 71:5, s. 717-724
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this paper is to establish and quantify different operational goals and control strategies in autothermal thermophilic aerobic digestion (ATAD). This technology appears as an alternative to conventional sludge digestion systems. During the batch-mode reaction, high temperatures promote sludge stabilization and pasteurization. The digester temperature is usually the only online, robust, measurable variable. The average temperature can be regulated by manipulating both the air injection and the sludge retention time. An improved performance of diverse biochemical variables can be achieved through proper manipulation of these inputs. However, a better quality of treated sludge usually implies major operating costs or a lower production rate. Thus, quality, production and cost indices are defined to quantify the outcomes of the treatment. Based on these, tradeoff control strategies are proposed and illustrated through some examples. This paper's results are relevant to guide plant operators, to design automatic control systems and to compare or evaluate the control performance on ATAD systems.
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| 7. |
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| 8. |
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| 9. |
- Zambrano, Jesús, et al.
(författare)
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Gaussian process regression for monitoring a secondary settler
- 2015
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Ingår i: Proc. 2nd IWA Conference on New Developments in IT & Water. - : IWA Publishing.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- An approach based on Gaussian Process Regression for monitoring the sludge profile of a secondary settler is proposed. Gaussian Process is a probabilistic, nonparametric model with an uncertainty prediction. The approach is illustrated using data from a sensor measuring the sludge concentration in a settler as a function of the settler depth at Bromma wastewater treatment plant (WWTP). Results suggest that the approach is feasible for monitoring and fault detection of the sludge settling process.
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| 10. |
- Zambrano, Jesús, et al.
(författare)
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Optimal steady-state design of zone volumes of bioreactors with Monod growth kinetics
- 2015
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Ingår i: Biochemical Engineering Journal. - : Elsevier BV. - 1369-703X .- 1873-295X. ; 100, s. 59-66
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with steady-state analysis and design of bioreactors consisting of a number of completely stirred tank reactors (CSTRs) in series. The study is confined to one consumed (substrate) and one consuming constituent (biomass). The specific microbial growth rate is assumed to be described by Monod kinetics. The death of biomass is assumed to be negligible. Two optimal design problems for a large number of CSTRs in series are studied: to minimize the effluent substrate concentration for a given total volume, and to minimize the total volume for a given effluent substrate concentration. As an appealing alternative to solve these problems numerically, it is proposed to consider the asymptotic case where the number of CSTRs tends to infinity. This is shown to correspond to one CSTR in series with a plug flow reactor (PFR). A CSTR with a sufficient large volume is needed to avoid wash-out of the biomass. The main result is that both design problems for the CSTR + PFR configuration have the same solution with respect to the optimal volume of the CSTR, which is given as an explicit function of the incoming substrate concentration, the volumetric flow rate and the coefficients of the Monod growth rate function. Numerical results indicate that the plug flow approach may be used as a feasible design procedure even for a reasonably low number of CSTRs in series.
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