Biomedical subjects

D Vrecko

Publications and source records attributed to D Vrecko.

5 recordsLinked to original sources

PubMed2003

Feedforward-feedback control of an activated sludge process: a simulation study.

In this paper a simulated plant based on a wastewater treatment benchmark is used to evaluate a number of controllers. Feedforward-feedback controllers for dissolved oxygen set-point and external carbon flow, and feedforward controller for internal recycle flow are evaluated separately and altogether. In the feedforward parts of the controllers, static physical models are incorporated in the control laws. The feedback parts of the controllers are used to compensate for model approximations. A simulation study shows that feedforward-feedback control of the activated sludge plant is more successful than standard PI control in meeting the effluent standards and reducing operational costs.

Automation↗

PubMed2002

Wastewater treatment benchmark: what can be achieved with simple control?

In this paper a simple control strategy is applied to and assessed on the wastewater treatment benchmark. The controllers used in the presented control strategy are PI controllers, feedforward control and a step-feed procedure. The controlled variables are not directly the effluent concentrations but other process variables which have an effect on the effluent. The setting of set-points is also analyzed to select the values with the best performance. Set-point analysis has shown that with an optimal setting of set-points under stormy influent conditions, the achieved plant performance is also retained for rainy and dry influent conditions. The evaluation of plant performance indicates that with the proposed control strategy, a lower number of effluent violations has been achieved, as well as lower energy consumption and lower sludge production, when compared to results published up to now. Only the effluent quality criterion deteriorated.

Algorithms↗

PubMed2002

Simulation study supporting wastewater treatment plant upgrading.

The paper presents a study where upgrading of an existing wastewater treatment plant was supported by simulation. The aim of the work was to decide between two technologies to improve nitrogen removal: a conventional activated sludge process (ASP) and a moving bed biofilm reactor (MBBR). To perform simulations, the mathematical models of both processes were designed. The models were calibrated based on data from ASP and MBBR pilot plants operating in parallel on the existing plant. Only two kinetic parameters needed to be adjusted to represent the real plant behaviour. Steady-state analyses have shown a similar efficiency of both processes in relation to carbon removal, but improved performance of MBBR in relation to nitrogen removal. Better performance of MBBR can be expected especially at low temperatures. Simulations have not confirmed the expected less volume required for the MBBR process. Finally, the MBBR was chosen for plant upgrading. The developed process model will be further used to evaluate the final plant configuration and to optimise the plant operating parameters.

Biofilms↗

PubMed2001

A new modified Smith predictor: the concept, design and tuning.

The paper presents a new modified Smith predictor (MSP) for processes with a long time delay. The MSP appears as an extension of the double controller-scheme (DCS) proposed by Tian and Gao. The important feature of the MSP is that the trade-off between disturbance rejection and robustness to variations in process parameters can be adjusted by means of a single free parameter. The main contribution of the paper concerns tuning of the MSP, which relies on a combination of magnitude optimum criterion with process parameterisation based on multiple integrals of the open-loop step response. In a simulation study the performance of the MSP is compared with that of two known controllers for time delay systems, i.e. DCS of Tian and Gao and Hägglund's predictive PI controller. The results show the advantage of the MSP compared to the two other controllers.

Journal Article↗

PubMed2001

System analysis for optimal control of a wastewater treatment benchmark.

The paper presents an analysis and optimisation of a wastewater treatment benchmark. The benchmark is a simulation environment defining a plant layout, simulation model, influent data, test procedures and evaluating criteria that should be used for comparing different control strategies. In this paper an analysis of the benchmark which addresses the influences of potential manipulated variables on control performance under different operating conditions is presented. In the study optimisation is used to define the optimal values of the manipulated variables under constant as well as dynamic influent conditions. The results indicate that such an analysis and optimisation give important information about the manipulated variables under varying influent conditions and consequently about possible control strategies.

Computer Simulation↗