Pilot Scale Application of Microwave Technology for Dairy Manure Treatment and Nutrient Recovery Through Struvite Crystallization
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PILOT SCALE APPLICATION OF MICROWAVE TECHNOLOGY FOR DAIRY MANURE TREATMENT AND NUTRIENT RECOVERY THROUGH STRUVITE CRYSTALLIZATION by HUI ZHANG B.Sc., Queen’s University, 2008 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in (Civil Engineering) UNIVERSITY OF BRITISH COLUMBIA (Vancouver) August 2013 © Hui Zhang, 2013 Abstract Excessive use of nutrients in agriculture has been significant surface and groundwater pollution sources. A pilot scale treatment process was developed for the purposes of phosphorus and ammonia recovery from dairy manure slurry. A novel advanced oxidation process combining hydrogen peroxide, microwave, and sulphuric acid was studied for its abilities to solubilise nutrients and metals in manure. The treated manure was then used for struvite crystallization to recover phosphates and ammonia in a commercially viable fertilizer form. Using dairy manure, as a phosphate source for struvite crystallization, had some foreseeable challenges. The majority of phosphorus in dairy manure slurry was insoluble, thus unsuitable for struvite crystallization. A synergistic nutrient solubilisation effect was found when manure was treated. As high as 101.7 ± 4.3% of total phosphorus was solubilised as phosphate, and 94.9 ± 4.7% of total nitrogen was solubilised as ammonia. High suspended solids concentration in manure slurry, thought to impede struvite crystallization, was also overcome through microwave treatment to destabilise manure solids from suspension. As high as 2.00 Log reduction in total suspended solids was achieved by gravity clarification. Manure contains high levels of calcium that would compete against struvite for phosphate precipitation. Oxalic acid was tested as a potential reagent to use for calcium removal from dairy manure. Up to 97.2% soluble Ca removal, by calcium oxalate precipitation was observed. The treated dairy manure was then used as influent material for struvite crystallization. Under various reaction conditions, it was found that phosphorus reduction between 69% and 99% was achievable. Roughly 25% nitrogen removal was observed under all reactor conditions. An interesting observation from the crystallization experiments was that pellet morphologies and compositions varied with reaction conditions. The potassium containing mineral hazenite was ii found to coexist in the struvite pellets. The ability to extract potassium from dairy manure was not only beneficial to the dairy industry, but may also create a fertilizer of higher economical and nutritional value, than struvite alone. iii Preface This thesis is original, unpublished, independent work by the author, Hui Zhang. The apparatuses used in this study (as described in Chapter 2) were based on the design of Wayne Lo, and modified by myself to better suit the scopes of this research. The model used for predicting struvite crystallization was created by Daniel Potts. All data presented henceforth, were generated from my studies conducted at the Dairy Education and Research Centre (Agassiz, B.C), in collaboration with the Department of Environmental Engineering, at the University of British Columbia, Point Grey campus. iv Table of Contents Abstract .......................................................................................................................................... ii Preface ........................................................................................................................................... iv Table of Contents ...........................................................................................................................v List of Tables ............................................................................................................................... vii List of Figures ............................................................................................................................. viii List of Abbreviations ................................................................................................................... ix Acknowledgements ..................................................................................................................... xi Chapter 1 Introduction..................................................................................................................1 1.1 Phosphorus ..........................................................................................................................2 1.2 Dairy Manure ......................................................................................................................4 1.2.1 Manure Characteristics .............................................................................................4 1.2.2 Dairy Manure Treatment and Uses ...........................................................................6 1.2.3 Environmental Implications ......................................................................................9 1.2.3.1 Phosphorus ....................................................................................................11 1.2.3.2 Notrogen .......................................................................................................12 1.3 Microwave Technologgy ..................................................................................................13 1.4 Struvite Crystallization .....................................................................................................18 1.5 Purpose and Scope ............................................................................................................23 Chapter 2 Pilot Plant Design and Operation .............................................................................25 2.1 Peroxide/Microwave Advanced Oxidation Process with Acid.........................................26 2.2 Liquid/Solid Separation and Calcium Removal ...............................................................31 2.3 Struvite Crystallizer ..........................................................................................................34 + Chapter 3 H2O2/MW/H -AOP ....................................................................................................38 3.1 Introduction .......................................................................................................................38 3.2 Materials and Methods......................................................................................................44 3.2.1 Constituent Analysis ...............................................................................................44 3.2.2 Manure ....................................................................................................................45 3.2.3 Chemicals ...............................................................................................................45 + 3.2.4 H2O2/MW/H -AOP .................................................................................................45 3.2.5 Coagulation/Flocculation and Settling of Manure Solids .......................................47 3.3 Results and Discussion .....................................................................................................47 3.3.1 Untreated Manure Characteristics ..........................................................................47 3.3.2 Nutrient Solubilisation ............................................................................................50 3.3.3 Gravity Clarification ...............................................................................................62 3.4 Conclusion ........................................................................................................................68 Chapter 4 Calcium Removal .......................................................................................................70 4.1 Introduction .......................................................................................................................70 4.2 Materials and Methods......................................................................................................73 + 4.2.1 Treatment of H2O2/MW/H -AOP Effluent with Oxalic Acid ................................73 4.2.2 Analysis ..................................................................................................................74 4.3 Results and Discussion .....................................................................................................74 v 4.4 Conclusion ........................................................................................................................79 Chapter 5 Struvite Recovery.......................................................................................................80 5.1 Introduction .......................................................................................................................80 5.2 Materials and Methods......................................................................................................84 5.2.1 Influent Material .....................................................................................................84 5.2.2 Chemicals ...............................................................................................................85 5.2.3 Crystallizer Model ..................................................................................................86 5.2.4 Experimental Reactor Conditions ...........................................................................87 5.2.5