Control And Decision Strategies In Wastewater Treatment Plants For Operation Improvement 1st Ed. 2017

This book examines the operation of biological wastewater treatment plants (WWTPs), with a focus on maintaining effluent water quality while keeping operational costs within constrained limits. It includes control operation and decision schemes and is based on the use of benchmarking scenarios that yield easily reproducible results that readers can implement for their own solutions. The final criterion is the effect of the applied control strategy on plant performance – specifically, improving effluent quality, reducing costs and avoiding violations of established effluent limits. The evaluation of the different control strategies is achieved with the help of two Benchmark Simulation Models (BSM1, BSM2). Given the complexity of the biological and biochemical processes involved and the major fluctuations in the influent flow rate, controlling WWTPs poses a serious challenge. Further, the importance of control goal formulation and control structure design in relation to WWTP process control is widely recognized. Of particular interest are the regulations governing the compliance with effluent criteria. Authorities measure compliance with these criteria on the basis of long or short timeframes, and the legal constraints imposed on effluent pollutant concentrations are among the most essential aspects of control structures for WWTPs. This book explores all these facets in detail. Preface 6 Contents 8 Abbreviations 11 1 Introduction 13 1.1 Motivation 13 1.2 Water Quality and Plant Operation 14 1.3 Book Outline 15 2 Process Modelling and Simulation Scenarios 16 2.1 Working Scenarios 16 2.1.1 Benchmark Simulation Model No. 1 17 2.1.2 Benchmark Simulation Model No. 2 21 2.2 Basic Plant Operation 24 2.3 Summary 26 3 Control Approaches 27 3.1 Model Predictive Control 27 3.1.1 Introduction 27 3.1.2 MPC Principle 28 3.1.3 Predictive Model Identification 30 3.1.4 Tuning Parameters 31 3.1.5 Feedforward Compensation 32 3.2 Fuzzy Control 32 3.2.1 Introduction 32 3.2.2 Fuzzy Logic Controllers 33 3.2.3 Fuzzy Sets 34 3.2.4 Fuzzy Inference 37 3.3 Artificial Neural Networks 39 3.3.1 Introduction 39 3.3.2 The Artificial Neuron 39 3.3.3 Types of Artificial Neural Networks 41 3.3.4 Training of the ANN 42 3.4 Summary 43 4 Tracking Improvement of the Basic Lower Level Loops 44 4.1 Applying Model Predictive Control Plus Feedforward Compensation 44 4.2 Simulation Results 47 4.2.1 SO,5 and SNO,2 Control 47 4.2.2 SO,3 and SO,4 Control 49 4.3 Summary 51 5 Variable Dissolved Oxygen Set-Points Operation 53 5.1 Higher Level Control Alternatives 53 5.1.1 Proposed Alternatives 53 5.1.2 Controllers Tuning 54 5.1.3 Simulations Results 60 5.2 Application of Variable Dissolved Oxygen in the Three Aerobic Reactors 66 5.2.1 Controllers Tuning 67 5.2.2 Simulations Results 70 5.3 Summary 73 6 Denitrification and Nitrification Processes Improvement for Avoiding Pollutants Limits Violations in the Effluent 75 6.1 SNtot,e Violations Removal 75 6.1.1 Controllers Tuning 76 6.1.2 Considerations for Rain and Storm Influents 79 6.2 SNH,e Violations Removal 79 6.2.1 Controllers Tuning 80 6.2.2 Considerations for Rain and Storm Influents 83 6.3 Simulation Results 84 6.3.1 SNtot,e Violations Removal 84 6.3.2 SNH,e Violations Removal 87 6.3.3 SNtot,e and SNH,e Violations Removal 89 6.4 Summary 92 7 Effluent Predictions for Violations Risk Detection 96 7.1 Implementation of Artificial Neural Networks 96 7.2 Simulation Results 99 7.3 Summary 102 8 Advanced Decision Control System 103 8.1 SO,4, SO,5 and SNO,2 Tracking 103 8.2 Manipulation of SO Set-Points, qEC and Qa 106 8.2.1 Fuzzy Controller for EQI and OCI Reduction 107 8.2.2 Fuzzy Controllers for SNtot,e Violations Removal 107 8.2.3 Fuzzy Controller for SNHe Violations Removal 109 8.3 Simulation Results 109 8.4 Summary 114 9 Concluding Remarks 117 Appendix A Pareto Optimality 120 References 125 Front Matter....Pages i-xii Introduction....Pages 1-3 Process Modelling and Simulation Scenarios....Pages 5-15 Control Approaches....Pages 17-33 Tracking Improvement of the Basic Lower Level Loops....Pages 35-43 Variable Dissolved Oxygen Set-Points Operation....Pages 45-66 Denitrification and Nitrification Processes Improvement for Avoiding Pollutants Limits Violations in the Effluent....Pages 67-87 Effluent Predictions for Violations Risk Detection....Pages 89-95 Advanced Decision Control System....Pages 97-110 Concluding Remarks....Pages 111-113 Back Matter....Pages 115-124