Marian Barbu

QFT robust control of a wastewater treatment process

Abstract The paper deals with the wastewater treatment process control using QFT (Quantitative Feedback Theory) techniques. The aim of the control is to obtain an effluent having the substrate concentration within the standard limits established by law (under 20 mg/l). It has been admitted variable operating regimes in large limits. Three main regimes have been taken into account: rain, normal, and drought. In these conditions two aspects were considered: a QFT controller designed to assure good properties for the three regimes mentioned before; a control structure that adjusts the dissolved oxygen setpoint as a function of the influent regime. The purpose is to stabilize the operating regime with respect to the quality variable (the effluent substrate concentration) and the command variable (the dilution rate).

Modeling and control of a multipurpose biotechnological plant. Photobioreactor modeling

The present paper is the first of a series of two papers that concerns the modeling of a complex multipurpose biotechnological plant that consist in two interconnected subsystems, namely an anaerobic digestor and a photobioreactor. The paper is presenting a complex analytical model for the photobioreactor that embeds the effect of pH on the photosynthetic growth of microalgae. The static characteristics of the multivariable non-square system are discussed along with the solution for its reduction when control strategies are aimed. Simplified dynamic models for the design of control loops were obtained through Hankel analysis.

Experimental Case Study

In order to be shown in detail, the design process algorithm (see Fig. 2 in Chap. “ Structural Design of the mCCHP-RES System”) was divided into two stages, namely structural design and functional design. In Chap. “ Structural Design of the mCCHP-RES System” was presented the first stage while in Chap. “ Functional Design of the mCCHP-RES System” was presented the second. Here it is shown a concrete example, which consists in the design of mCCHP system for a familiar type housing. The design was done in accordance with the algorithm, which is shown in Fig. 2 in Chap. “ Structural Design of the mCCHP-RES System” and described in Chaps. “ Structural Design of the mCCHP-RES System” and “ Functional Design of the mCCHP-RES System” in detail. The 12 paragraphs of this chapter contain data resulting from application of the 12 steps of the algorithm. Testing of the real mCCHP system that has been achieved through the practical application of this algorithm confirmed the algorithm validity.

Modelling and performance analysis of an urban wastewater treatment plant

The paper deals with modelling and performance analysis of an existent wastewater treatment plant which serves a town with a population ranged between 250000 and 300000 inhabitants, based on a complex mathematical model developed in SIMBA software. The model was simulated in all three characteristics regimes (dry, rain and storm) considering an influent proposed in BSM1 model (Benchmark Simulation Model). The analysis consisted in calculus of specific indicators of “limit” type (they belong to Romanian legislation in the field of the water quality) and of quality and cost indicators which are defined in BSM2 model, in open and closed loop. In closed loop regime two PI controllers were designed and implemented: the first controls the dissolved oxygen concentration in the tank T4 and the second controls the nitrate concentration in the tank T2 through the modification of the internal recycling flow.

Robust control of an activated sludge wastewater treatment process

This paper presents the application of the Quantitative Feedback Theory (QFT) method to a wastewater treatment plant with activated sludge. The control strategy contains two control loops, with different dynamics, the controlled variables being the dissolved oxygen in the aerobic tank and the nitrate concentration in the effluent. The control strategy was validated on a ASM1 based wastewater treatment plant implemented in SIMBA® and considering a time-varying profile of the influent both in terms of the flow and the concentrations of wastewater compounds.

QFT Control of Dissolved Oxygen Concentration in a Wastewater Treatment Pilot Plant

Abstract The paper deals with the robust control of the dissolved oxygen concentration in the case of wastewater treatment processes from milk and beer industry. The QFT robust control method has been chosen for the dissolved oxygen concentration control. Firstly the dissolved oxygen control loop was identified. The QFT controller and prefilter were designed so that the behaviour of the closed loop system be bounded by the limits (upper and lower) imposed to the system. The QFT control of the dissolved oxygen concentration was tested using an experimentally pilot plant that is also presented in the paper.

Modelling of a multipurpose biotechnological plant in view of automatic control. Process modelling and control properties analysis

This work continues the paper [1] and it deals with a multipurpose biotechnological plant which includes a photobioreactor interconnected with an anaerobic digester. In the paper linearized models of reduced order for anaerobic digester and for the entire biotechnological plant are obtained. These models of reduced order are determined from detailed models of 35th order for anaerobic digester and of 51th order for the entire plant using Hankel analysis. It is proposed a control structure of the plant in which the photobioreactors control loop drives the one of anaerobic digester. The results obtained in [1] and in the present paper offer the necessary information (i.e. models and control structure configurations) to the controllers design for the control loops of the multipurpose biotechnological plant.

Analysis of phosphorus removal performances in a municipal treatment plant

This paper addresses the performance modeling and analysis in the case of a wastewater treatment system for removal of phosphorus, consisting a biological reactor and a secondary settling tank. The mathematical model was developed in the SIMBA simulation environment. The system is based on an actual municipal wastewater treatment plant. The implemented architecture is similar to that in BSM1 (the digestion anaerobic process is not treated) so that the Activated Sludge Model 2d is used to describe the variables and processes of the wastewater treatment plant. The control strategies were simulated, using the model of an influent having loads corresponding to the real plant, for a dry regime, in open and closed loop. As part of the analyzed strategies, PI-type regulators were used for the control of dissolved oxygen concentration, internal recirculation and ferric chloride addition, which accelerates the phosphorus precipitation.

A Binary Hybrid Topology Particle Swarm Optimization algorithm for sewer network discharge

In this paper, a Binary Hybrid Topology Particle Swarm Optimization algorithm is used to solve a dynamic optimization problem, namely the sewer network discharge problem defined like a binary optimization problem. A method of implementing this meta-heuristic adapted to control optimization problems is proposed. The main contribution of this paper is the amelioration of the local topology, as it is presented in the usual form of this meta-heuristic. A local descent deterministic algorithm is included in the procedure that implements this topology. The meta-heuristic algorithm has been implemented in two versions: without and with the local descent algorithm. The computational results are analyzed and the conclusion is drawn using some statistical parameters.

Sewer network discharge control using a multiagent approach

This paper proposes a distributed controller for a sewer network aiming to minimize the total overflow volume generated by the influent collected in its area, in the horizon of the control problem. The sewer network is modeled as a nonlinear discrete dynamic system. The control objective leads to an optimization problem with constraints on control and state variables. Instead of solving this optimization problem in order to obtain an optimal controller, a multi-agent system is used as a distributed controller. The main advantage is the very small complexity of this approach in comparison with the optimization problem. The numerical tests are very encouraging.