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CORNELL CEE 453 - Phosphorus removal

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Nutrient Removal ProjectBiological Phosphorus Removal and pHTable of ContentsIntroduction:Objectives:Methods:Plant Setup and ConstructionSampling and Phosphorus AnalysisPH controlTitrationResults and DiscussionConclusion:Nutrient Removal ProjectBiological Phosphorus Removal and pHDawn SedorovichNami TanakaSintana VergaraTracy WiseXinning Zhang05/09/2003CEE 453Dr. Monroe Weber-ShirkAbstract:Phosphorus (P) pollution in streams and lakes can cause eutrophication, leading toalgal blooms, fish kills and overall decreased water quality. As a result, phosphorusremoval in wastewater treatment plants is a high priority to avoid contamination of receiving waters upon release of the treated effluent. Relevant literature has indicated that P removal has a strong correlation to pH, with a higher percentage of P removal occurring at lower pH values. We created a miniature model of a wastewater treatment plant and implemented pH control through a computer-controlled acid feed to determine the pH corresponding to the maximum P removal. Samples of the wastewater were regularly taken to determine P concentration. In addition, dissolved oxygen, temperature,and pH values were monitored throughout plant operation. Contrary to published research, our analysis suggests that high pH values corresponded to higher phosphorus removal. However, further research should be conducted to validate our results.Table of ContentsIntroduction:......................................................................................................................3Objectives:..........................................................................................................................4Methods:.............................................................................................................................5Plant Setup and Construction...........................................................................................5Sampling and Phosphorus Analysis...............................................................................10PH control.........................................................................................................................12Titration............................................................................................................................16Conclusion:.......................................................................................................................25Suggestions and Recommendations…………………… ………………………………26Introduction:2A high phosphorous content in treated wastewater can lead to eutrophication of the receiving water, since phosphorous is an essential nutrient needed for algae growth. Eutrophication is caused by the overabundance of nutrients in water, and it can result in water quality problems such as fish kills, noxious tastes and odors, clogged pipelines and restricted recreation. Prior to the discharge of treated wastewater, municipal wastewater treatment plants are required to remove as much phosphorous as possible in order to avoid eutrophication. Phosphorous removal can be done chemically, biologically or a using a combination of both procedures. When phosphorous removal is done chemically,phosphorous is precipitated as an insoluble metal phosphate. This can be achieved by adding ferric sulfate, ferric chloride or aluminum sulfate to wastewater. However, this method results in excessive sludge production and is often considered costly.Biological phosphorus removal is more economical and environmentally sound toour environment. This method requires the addition of an anaerobic state to the activated sludge system. During the anaerobic state, phosphorus-removing microorganisms releasephosphorus in order to produce energy to consume the fermentation products generated by other heterotrophic microorganisms. In the aerobic state, these same phosphorous-removing organisms produce energy by oxidizing the stored fermentation products while simultaneously accumulating intracellular phosphate which they store as poly-p. Thus, an accumulation of phosphate as poly-p in excess of normal metabolic requirements reduces the phosphorus content in the effluent1.Some studies have found that acidic environments (pH of 5.5 – 5.6) allow phosphorous-removing microorganisms to produce more poly-p, increasing the uptake of 1 Park J. K. Wastewater Characterization for Evaluation of Biological Phosphorus Removalhttp://www.dnr.state.wi.us/org/water/wm/ww/biophos/1intro.htm3phosphorous2. Currently, the most practical phosphorus removal is achieved at a pH value of 7.53. A thorough understanding of the optimal pH for biological phosphorus removal will enable us to determine the most efficient approach to the phosphorous removal process.Objectives:The objectives of the research project were to investigate the optimal pH for phosphorous removal, and to integrate a pH control system with the existing NRP 2003 LabVIEW software written by Dr. Monroe Weber-Shirk. This will include adding an anaerobic phase and an automated pH control structure to the NRP code. The pH control should be capable of adjusting and maintaining the pH of the activated sludge tank to a user-input pH value. Methods: Plant Setup and ConstructionThe batch reactor was a 5 L plastic container. The tank was placed on a stir plate, and a magnetic stir bar was kept in the tank to provide mixing during the desired states. In order to model a working wastewater treatment plant, the team set up the plant to accommodate six different phases: fill with feed, fill with water, anaerobic, aerate, settle, and drain. The anaerobic state, in which the tank was not given oxygen, was added after the other five were established in preparation of exploring phosphorus uptake under differing pH conditions. We also knew that we would want to monitor the temperature, the dissolved oxygen level, and, later, pH throughout plant operation. In addition, we 2 McGrath J.W. Phosphate Removal: A Novel Approach http://www.qub.ac.uk/envres/EarthAirWater/phosphate_removal.htm#TopPage3 ibid4needed an air diffuser to oxygenate the tank, and an acid feed to control the pH in the tank.The inputs to the batch reactor were water, feed (simulating waste), and acid. The water came from a large tank in the Environmental Teaching Laboratory. This tank had periodic additions of water and stock solutions B and C containing metals4. The feed (stock solution A),


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