Biomedical subjects

N Hvala

Publications and source records attributed to N Hvala.

6 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

Experimental design of an optimal phase duration control strategy used in batch biological wastewater treatment.

The paper presents the design of an algorithm used in control of a sequencing batch reactor (SBR) for wastewater treatment. The algorithm is used for the on-line optimization of the batch phases duration which should be applied due to the variable input wastewater. Compared to an operation with fixed times of batch phases, this kind of a control strategy improves the treatment quality and reduces energy consumption. The designed control algorithm is based on following the course of some simple indirect process variables (i.e. redox potential, dissolved oxygen concentration and pH), and automatic recognition of the characteristic patterns in their time profile. The algorithm acts on filtered on-line signals and is based on heuristic rules. The control strategy was developed and tested on a laboratory pilot plant. To facilitate the experimentation, the pilot plant was superimposed by a computer-supported experimental environment that enabled: (i) easy access to all data (on-line signals, laboratory measurements, batch parameters) needed for the design of the algorithm, (ii) the immediate application of the algorithm designed off-line in the Matlab package also in real-time control. When testing on the pilot plant, the control strategy demonstrated good agreement between the proposed completion times and actual terminations of the desired biodegradation processes.

Aerobiosis↗

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↗

PubMedDate not supplied

Design of a sequencing batch reactor sequence with an input load partition in a simulation-based experimental environment.

A study is presented that considers optimization of a sequencing batch reactor (SBR) operational sequence. Optimization is performed with the aid of a laboratory pilot plant and a process model. The model was included in the study to facilitate a search for optimal operating conditions because performing experiments solely on the pilot plant would be rather extensive, expensive, and time-consuming. The model used in the study is the well-known Activated Sludge Model No.1 with minor modifications. The optimization addresses a split-feed operating mode with input load partitioned into two parts and with two successions of aerobic-anoxic phases. In the study, the duration of batch phases and the time of the second input addition are optimized so that the desired effluent nitrogen concentration is achieved and the need for external carbon addition in the anoxic phase is reduced or eliminated. When an optimal SBR sequence computed by the model was verified on the pilot plant, better performance of the actual process was also achieved, although some phenomena were observed that were not predicted by the model. Results of the study indicate that the available wastewater treatment plant models, although a simplification of reality, can be usefully applied for process optimization.

Equipment Design↗