Jens Alex

Generation of diurnal variation for influent data for dynamic simulation

When using dynamic simulation for fine tuning of the design of activated sludge (AS) plants diurnal variations of influent data are required. For this application usually only data from the design process and no measured data are available. In this paper a simple method to generate diurnal variations of wastewater flow and concentrations is described. The aim is to generate realistic influent data in terms of flow, concentrations and TKN/COD ratios and not to predict the influent of the AS plant in detail. The work has been prepared within the framework of HSG-Sim (Hochschulgruppe Simulation, http://www.hsgsim.org), a group of researchers from Germany, Austria, Luxembourg, Poland, the Netherlands and Switzerland.

Systematic Design of Distributed Controllers for Sewer Networks

A novel concept for a systematic design procedure of a distributed controller network for global control of a sewer network is proposed. This concept is based on two simple controller types (local throttle controller, supervisory controller) which are connected systematically based on the structure of the sewer network and the available throttle and storage structures. The controllers are based on simple algorithms (nonlinear P-control, simple prediction models) which can be implemented in standard programmable logic controllers (PLCs). Design rules for the controller parameters are available. An appropriate simulation system allowing the design, test and validation of the developed concept which has been set up. The simulation system allows the description of the controllers using a standard PLC programming language (IEC 61131 ST). Finally, an example is presented to demonstrate the ability of the control concept to utilise a high percentage of the theoretically available improvement potential for automatic control. The approach presented is expected to be easily applicable in real cases and to reduce the typical effort required for the application of automatic control to sewer networks by at least one order of magnitude.

Predictive control of nitrogen removal in WWTPS using parsimonious models

Abstract In the paper, control possibilities for the nitrogen removal process within activated sludge wastewater treatment plants are discussed. A predictive controller is introduced which aims to reduce the peaks in effluent concentration for ammonia nitrogen. Additionally, the controller improves the overall nitrogen removal using less aeration energy. A parsimonious deterministic model is used for the prediction of the effluent ammonia concentration. The main parameter of the model is used for the model adaptation. The performance of the developed controller is evaluated using a benchmark simulation model of a treatment plant introduced by an international work group.

Impacts of onsite greywater reuse on wastewater systems

Together with significant water savings that onsite greywater reuse (GWR) may provide, it may also affect the performance of urban sewer systems and wastewater treatment plants (WWTPs). In order to examine these effects, an integrated stochastic simulation system for GWR in urban areas was developed. The model includes stochastic generators of domestic wastewater streams and gross solids (GSs), a sewer network model which includes hydrodynamic simulation and a GS transport module, and a dynamic process model of the WWTP. The developed model was applied to a case study site in Israel. For the validation of the sewer simulator, field experiments in a real sewer segment were conducted. The paper presents the integration and implementation of these modules and depicts the results of the effects of various GWR scenarios on GS movement in sewers and on the performance of the WWTP.

Development of a model for activated sludge aeration systems: linking air supply, distribution, and demand

During the design of a water resource recovery facility, it is becoming industry practice to use simulation software to assist with process design. Aeration is one of the key components of the activated sludge process, and is one of the most important aspects of modelling wastewater treatment systems. However, aeration systems are typically not modelled in detail in most wastewater treatment process modelling studies. A comprehensive dynamic aeration system model has been developed that captures both air supply and demand. The model includes sub-models for blowers, pipes, fittings, and valves. An extended diffuser model predicts both oxygen transfer efficiency within an aeration basin and pressure drop across the diffusers. The aeration system model allows engineers to analyse aeration systems as a whole to determine biological air requirements, blower performance, air distribution, control valve impacts, controller design and tuning, and energy costs. This enables engineers to trouble-shoot the entire aeration system including process, equipment and controls. It also allows much more realistic design of these highly complex systems.

Zur Nutzung von On-line-Modellen für die Regelung von Kläranlagen

Dr.-Ing. Ulrich Jumar ist Bereichsleiter Steuerung und Regelung im Forschungsinstitut ifak e.V. Magdeburg. Hauptarbeitsfelder sind Advanced-Control-Anwendungen im Umwellbereich, Modellierung und Simulation von Systemen des Straßenverkehrs, Verkehrsmanagement. In der GMA Gesellschaft für Meßund Automatisierungstechnik leitet er den Fachbereich Anwendungsfelder der Leitund Automatisierungstechnik.

Simulationsplattform zum integrierten Prozess- und Automatisierungsentwurf von Abwassersystemen

Zusammenfassung In diesem Beitrag wird eine neue Simulationsplattform für Abwassersysteme und insbesondere Kläranlagen vorgestellt, mit der neben der verfahrenstechnischen Funktion vor allem Betriebsführungskonzepte und Steuerungs- und Regelungsvarianten untersucht werden können. Besonderes Augenmerk bei der Entwicklung des Simulationssystems lag auf der Gestaltung der Bedienungsführung, um auch unerfahrenen Anwendern einen schnellen intuitiven Einstieg in die verfahrenstechnische und regelungstechnische Simulation dieser Anlagen zu ermöglichen. Neben der Fließbild-orientierten Erstellung des Modells der Verfahrenstechnik wird eine ständig wachsende Bibliothek von grafischen Funktionsblöcken entwickelt, um automatisierungstechnische Funktionen (u. a. Petri-Netze, Prädiktivregler) zu beschreiben.

Benchmark-Modell für anlagenweite Kläranlagenregelungen (A Benchmark Model for Plant Wide Control of Waste Water Treatment Plants).

Zusammenfassung Für die Steuerung und Regelung von Kläranlagen wird in der Literatur eine unüberschaubare Anzahl von Konzepten und Varianten publiziert. Um unterschiedliche Ansätze objektiv bewerten und vergleichen zu können, wird in der hier vorgestellten Initiative ein Benchmark-System definiert, das aus einer Sammlung von Simulationskomponenten und einer Methodik zum objektiven, simulativen Vergleich unterschiedlicher Regelungskonzepte besteht. Die Nutzung dieses von einer Arbeitsgruppe der IWA — International Water Association entwickelten Benchmark-Systems wird durch die Analyse einer Auswahl typischer Kläranlagenregelungen demonstriert.

FORMALISED MODEL REPRESENTATION FOR WASTEWATER SYSTEMS

Abstract A fundamental pre-condition for the application of simulation is the availability of reliable models. Particular problems arise in the application of simulation for integrated process design of complex wastewater systems. The models necessary for this task have to include different sub-processes such as biological wastewater treatment, anaerobic digestion processes and also models of the control system. To deal with this problem this paper describes an approach on how (1) to follow strict mass conservation principles during model development and (2) how to use formalised model representation methods for model creation, exchange and analysis. The adaptation of the XML-based Systems Biology Mark-Up Language (SBML) to the area of wastewater modelling is proposed. The implementation of this approach in a simulation environment for practical control engineering tasks is demonstrated.

Dynamische Simulation komplexer Abwasserreinigungsprozesse

Biologische Klaranlagen mit erweiterter Stickstoff- und Phosphorelimination stellen zunehmend hohere Anspruche an die verfahrenstechnische Gestaltung und Dimensionierung, die Steuerung- und Regelung sowie die Betriebsfuhrung. Mit einem Werkzeug zur dynamische Simulation von Belebtschlamm-Klaranlagen konnen fur alle drei Aufgabenkomplexe wertvolle Beitrage geleistet werden. Die in diesem Beitrag vorgestellte Modellbibliothek fur das Simulationssystem Matlab ® /Simulink TM 1 wurde insbesondere zu Analyse, Entwurf und Optimierung von Steuerungen und Regelungen fur kommunale Klaranlagen entwickelt.