Clean Future Engineering, Inc.TABLE OF CONTENTSObjectives & MotivationsLaboratory MethodsAlgorithmsConstant Flow Rate AerationResultsOn/Off With Constant Flow RateResultsLinear Airflow Rate ControlResultsExponential Airflow Rate ControlResultsSimulation Model Based Airflow Rate ControlResultsAlgorithm Comparisons & ConclusionSuggestions and CommentsReferencesAppendix ANutrient Removal ProjectDissolved Oxygen Control AlgorithmsCEE 453- Laboratory Research in Environmental EngineeringCornell UniversityJanuary 14, 2019Clean Future Engineering, Inc.Dale MeckRoslyn OdumNick WobbrockTABLE OF CONTENTSObjectives & Motivations..........................................................................................3Laboratory Methods..................................................................................................4Algorithms.................................................................................................................5Constant Flow Rate Aeration......................................................................................................5Results......................................................................................................................................6On/Off With Constant Flow Rate.................................................................................................8Results......................................................................................................................................8Linear Airflow Rate Control......................................................................................................10Results....................................................................................................................................10Exponential Airflow Rate Control.............................................................................................12Results....................................................................................................................................12Simulation Model Based Airflow Rate Control.........................................................................14Results....................................................................................................................................16Algorithm Comparisons & Conclusion...................................................................19Suggestions and Comments.....................................................................................20References...............................................................................................................20Appendix A..............................................................................................................212Objectives & MotivationsThe purpose of this experiment was to determine the effectiveness of several computeralgorithms to control the dissolved oxygen levels in a sequencing batch wastewater treatmentreactor. In the treatment of organic waste, microorganisms consume dissolved oxygen forcellular respiration during the transformation of waste into cellular biomass. It is important tocontrol wastewater dissolved oxygen levels because optimum levels of dissolved oxygen in thereactor will allow microbial degradation and efficient oxygen transfer to conserve energy.Bubbling air through treatment reservoirs is the most common technique foraerating/oxygenating wastewater and it is also one of the largest expenses in the wastewatertreatment process. Often less than 10% of the oxygen pumped through wastewater will dissolveinto solution, and only the dissolved oxygen is accessible to microbes for degradation (Monroe,2004). Oxygen transfer efficiency depends on the dissolved oxygen concentration, the oxygenbubble size, the height of the wastewater column, and the temperature of the water. Unlike realworld waste reservoirs, our BOD concentration will drop within each aeration phase. Thiscauses the oxygen consumption rate to drop as well, necessitating an algorithm that responds to acontinually changing set of conditions. To maintain a constant DO level, the algorithms had toadapt to the changing DO levels and continually adjust the aeration rate. Throughout this projectwe attempted to improve each of our aeration algorithms by considering the strengths andweaknesses of the previous algorithms. We anticipate algorithms that consider the oxygenconsumption rate to be the most effective.We implemented five different algorithms using a LabView process control programcreated by Monroe Weber-Shirk at Cornell University. The algorithms, Constant Flow RateAeration, On/Off With Constant Flow Rate, Linear Airflow Rate Control, Exponential AirflowRate Control, and Simulation Model Based Airflow Rate Control, vary in intricacy, flexibilityand required inputs. In this project we compare, both statistically and qualitatively, the ability ofeach algorithm to maintain a constant dissolved oxygen level in our laboratory scale wastewatertreatment plant. 3Laboratory MethodsConventional water treatment plants are not typically sequencing batch reactors.However, in an undergraduate laboratory setting, this type of plant, illustrated schematically inFigure 1, is much more appropriate. The sequencing batch reactor used for this research consistsof a 6-L square plastic tank reactor (maximum liquid volume of 4-L). Stock 1 of the totalsynthetic waste, the feed composition used by Cicek, Franco et al. (Cicek, 1998) with somemodifications made by Weber-Shirk (Weber-Shirk, 2004), was stored in concentrated solutions inrefrigerators mounted above the laboratory workbench. The waste was metered into the reactorand diluted with Stock 2 and Stock 3 using a peristaltic pump. The tank reactor was positionedon a magnetic laboratory stir bar to insure adequate mixing. A pressure sensor was added to the bottom of the tank and calibrated to the container toallow for accurate reactor volume measurement. An emergency spill tube was also added to thereactor to insure the plant did not overflow in the event of a code error or a hardware failure.Oxygen was added to the reactor using an aeration stone connected to an airflow regulatingsystem composed of two solenoid valves and an air accumulator. A pictorial description of thesystem is given in