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ControlEngineeringPractice12(2004)357–373BenchmarkingcombinedbiologicalphosphorusandnitrogenremovalwastewatertreatmentprocessesKristV.Gernaey*,StenB.J^rgensenCAPEC,DepartmentofChemicalEngineering,TechnicalUniversityofDenmark,Building229,DK-2800Lyngby,DenmarkAccepted26March2003AbstractThispaperdescribestheimplementationofasimulationbenchmarkforstudyingtheinfluenceofcontrolstrategyimplementationsoncombinednitrogenandphosphorusremovalprocessesinabiologicalwastewatertreatmentplant.Thepresentedsimulationbenchmarkplantanditsperformancecriteriaaretoalargeextentbasedonthealreadyexistingnitrogenremovalsimulationbenchmark.Thepaperillustratesandmotivatestheselectionofthetreatmentplantlay-out,theselectionofthebiologicalprocessmodel,thedevelopmentofrealisticinfluentdisturbancescenariosfordry,rainandstormweatherconditionsrespectively,thedefinitionofperformanceindexesthatincludethephosphorusremovalprocesses,andtheselectionofasuitableoperatingpointfortheplant.Twocontrolloopswereimplemented:onefordissolvedoxygencontrolusingtheoxygentransfercoefficientKLaasmanipulatedvariable,thesecondonefornitratecontrolintheanoxiczoneusingtheinternalrecirculationflowrateasmanipulatedvariable.Dynamicsimulationsfordifferentdissolvedoxygensetpointsillustratethecomplexinteractionsinthisplant,andthenecessityforacontinuoustradeoffbetweensupplyingsufficientoxygentopromotenitrificationontheonehand,andtheneedforlowdissolvedoxygenconcentrationsontheotherhandtoallowsufficientdevelopmentofphosphorusaccumulatingorganisms.Thepotentialforaerationenergysavingsintheplantishighlightedbasedonthedissolvedoxygenprofilesresultingfromopenloopsimulationswithadynamicdryweatherinfluentscenario.Theinfluenceofthedissolvedoxygensetpointselectiononthenitratecontrolloopperformanceobservedinthesimulationsfurtherillustratestheneedforaplant-wideoptimizationapproachtoreachoptimalplantperformance.r2003ElsevierLtd.Allrightsreserved.Keywords:Benchmarkexamples;Performanceanalysis;Models;Environmentalengineering;Waterpollution1.Introduct