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Urine Source Separation

Permanent Link: http://ufdc.ufl.edu/UFE0043877/00001

Material Information

Title: Urine Source Separation Critical Literature Review and Novel Precipitation Control
Physical Description: 1 online resource (77 p.)
Language: english
Creator: Taylor, Kyle E
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2011

Subjects

Subjects / Keywords: nutrient -- recycling -- struvite -- urine
Environmental Engineering Sciences -- Dissertations, Academic -- UF
Genre: Environmental Engineering Sciences thesis, M.E.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Urine separation and treatment can provide many benefits, including nutrient recovery, reduced water and resource use, and lower capacity wastewater treatment plants. The environmental benefits are numerous but success of these systems depends greatly on process engineering and user acceptance. Laboratory scale studies have sought to optimize the recovery of a potentially valuable mineral, struvite, a magnesium phosphate mineral, from urine by precipitation. Few full-scale reactors for struvite precipitation have been implemented at this time. These units have shown good recovery of phosphorus but more research is needed to make them economically feasible and ensure maximum nutrient recovery. Urine separating units are hindered by clogging due to mineral precipitation triggered by urea hydrolysis, a process catalyzed by the enzyme urease which transforms the urea into ammonia and bicarbonate. The two most common mineral precipitates are hydroxyapatite (HAP), a calcium phosphate mineral, and struvite. Problematic precipitation, along with other usability issues, has resulted in variable success of urine separation units. Preliminary experiments were conducted to examine the removal of magnesium and calcium from synthetic urine using a cation exchange resin with the goal of preventing the formation of HAP and struvite. Cation exchange treatment showed good removal of both calcium and magnesium from the urine, with a preference for calcium. However, calculations showed that HAP and struvite were still supersaturated in the treated urine, which motivated subsequent precipitation studies. The goal of the precipitation studies was to study the rate and extent of mineral precipitation. A synthetic urine mixture was prepared to simulate urine after it had undergone cation exchange treatment and urea hydrolysis. Two batches of synthetic hydrolyzed urine were made: magnesium only and calcium only. The aged urine was dosed with different amounts of phosphate to observe the amount of calcium and magnesium precipitated from the urine. Results from the precipitation studies agreed with the stoichiometry for struvite precipitation (1:1 Mg:P) and HAP precipitation (5:3 Ca:P). This research is important because it provides new information about precipitation reactions in urine which is expected to improve the performance of waterless urinals and urine source separation technology.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Kyle E Taylor.
Thesis: Thesis (M.E.)--University of Florida, 2011.
Local: Adviser: Boyer, Treavor H.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2013-12-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2011
System ID: UFE0043877:00001

Permanent Link: http://ufdc.ufl.edu/UFE0043877/00001

Material Information

Title: Urine Source Separation Critical Literature Review and Novel Precipitation Control
Physical Description: 1 online resource (77 p.)
Language: english
Creator: Taylor, Kyle E
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2011

Subjects

Subjects / Keywords: nutrient -- recycling -- struvite -- urine
Environmental Engineering Sciences -- Dissertations, Academic -- UF
Genre: Environmental Engineering Sciences thesis, M.E.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Urine separation and treatment can provide many benefits, including nutrient recovery, reduced water and resource use, and lower capacity wastewater treatment plants. The environmental benefits are numerous but success of these systems depends greatly on process engineering and user acceptance. Laboratory scale studies have sought to optimize the recovery of a potentially valuable mineral, struvite, a magnesium phosphate mineral, from urine by precipitation. Few full-scale reactors for struvite precipitation have been implemented at this time. These units have shown good recovery of phosphorus but more research is needed to make them economically feasible and ensure maximum nutrient recovery. Urine separating units are hindered by clogging due to mineral precipitation triggered by urea hydrolysis, a process catalyzed by the enzyme urease which transforms the urea into ammonia and bicarbonate. The two most common mineral precipitates are hydroxyapatite (HAP), a calcium phosphate mineral, and struvite. Problematic precipitation, along with other usability issues, has resulted in variable success of urine separation units. Preliminary experiments were conducted to examine the removal of magnesium and calcium from synthetic urine using a cation exchange resin with the goal of preventing the formation of HAP and struvite. Cation exchange treatment showed good removal of both calcium and magnesium from the urine, with a preference for calcium. However, calculations showed that HAP and struvite were still supersaturated in the treated urine, which motivated subsequent precipitation studies. The goal of the precipitation studies was to study the rate and extent of mineral precipitation. A synthetic urine mixture was prepared to simulate urine after it had undergone cation exchange treatment and urea hydrolysis. Two batches of synthetic hydrolyzed urine were made: magnesium only and calcium only. The aged urine was dosed with different amounts of phosphate to observe the amount of calcium and magnesium precipitated from the urine. Results from the precipitation studies agreed with the stoichiometry for struvite precipitation (1:1 Mg:P) and HAP precipitation (5:3 Ca:P). This research is important because it provides new information about precipitation reactions in urine which is expected to improve the performance of waterless urinals and urine source separation technology.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Kyle E Taylor.
Thesis: Thesis (M.E.)--University of Florida, 2011.
Local: Adviser: Boyer, Treavor H.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2013-12-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2011
System ID: UFE0043877:00001


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1 URINE SOURCE SEPARATION : CRITICAL LITERATURE REVIEW AND NOVEL PRECIPITATION CONTROL By KYLE TAYLOR A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ENGINEERING UNIVERSITY OF FLORIDA 2011

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2 2011 Kyle Taylor

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3 To Nancy and Lara

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4 ACKNOWLEDGMENTS I thank my committee for being extremely generous with their time. Dr. Eric McLamore agreed to participate on two of my committ ees, and I would like to thank him for his graciousness. I have been lucky enough to have taken many classes with Dr. Joseph Delfino all of which have made me a more contentious engineer and a better scientist and from that this project has surely benefite d. He has also provided me with words of encouragement and support for which I am extremely grateful. With enormous patience and understanding, Dr. Treavor Boyer helped me see this project to completion. He dealt with my fickleness and insecurities and alw ays made me feel capable He provided me with helpful comments and guidance on multiple drafts which have dramatically increased the quality of the work His extensive knowledge, time, patience and enthusiasm for the project have been invaluable. I am so grateful to the Boyer research group for their feedback and friendship Special thanks to the people who put up with me after the end of the workday, RJ, my TA turned dance partner and friend, Stephanie, for being so encouraging and always willing to liste n, and to Chris, for providing me with much needed distractions and always being prepared to give me a citation. around awesomeness and the bountiful free services they offer. Mo rgan Hughes, my good friend and amazing digital artist, helped me turn my pathetic drawing into a true work of art. I owe a large part of my success in the lab to Ira Glass, Jad Abumrad, and Robe r t Krulwich, who accompanied me day in and day out of titrati ons. Grandpa and Computer have always been great sounding boards and I appreciate their loyalty and patience.

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5 My friends have provided me with so much over the past years, without which s. Rachel(s ) and Christina have kept with me even when I was completely rotten to be around and have never complained, they have made my time in Gainesville truly special. Lara has been with me through the saddest and happiest times in my life and my gratitude and love for her cannot be expressed in words. I am forever indebted to the Silver family, for letting me become a part of their family; at a time where I surely would have floundered they gave me love and support. I especially want to thank Jul ia, who braved the storm alongside me and encourage d and listened to me tirelessly, always making me feel loved and talented.

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6 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF TABLES ................................ ................................ ................................ ............ 8 LIST OF FIGURES ................................ ................................ ................................ .......... 9 LIST OF ABBREVIATIONS ................................ ................................ ........................... 11 ABSTRACT ................................ ................................ ................................ ................... 13 CHAPTER 1 OVERVIEW OF THESIS ................................ ................................ ........................... 15 2 CRITICAL LITERATURE REVIEW ................................ ................................ ............ 17 2.1 Overview and Objectives ................................ ................................ .................. 17 2.2 Environment ................................ ................................ ................................ ...... 18 2.3 Process Engineering ................................ ................................ ......................... 19 2.3.1 Laboratory Scale Struvite Precipitation R esearch ................................ ... 20 2.3.2 Implementa tion of Struvite Precipitation R eactors ................................ ... 22 2.4 User ................................ ................................ ................................ .................. 24 2.4.1 Usability Issues and Problematic P recipitation ................................ ........ 24 2.4.2 Overview of Real Life S ystems ................................ ............................... 26 3 LABORATORY RESEARCH GOALS, OBJECTIVES, AND LIMITATIONS .............. 37 4 M ATERIALS AND METHODS ................................ ................................ .................. 39 4.1 Ion Exchange Experiments using Fresh Urine ................................ .................. 39 4.1.1 Fresh Synthetic U rine ................................ ................................ .............. 39 4.1.2 Resin S elect ion and D osing ................................ ................................ .... 40 4.1.3 Batch T ests ................................ ................................ ............................. 41 4.2 Precipitation Experiments in Simulated Hydrolyzed Urine ................................ 41 4.2 .1 Calcium and Magnesium free Aged U rine ................................ .............. 41 4.2.2 Magnesium and Calcium Stock S olutions ................................ ............... 41 4.2.3 Precipitation E xperiments ................................ ................................ ........ 42 4.3 Phosphate Dosing Precipitation Experiments ................................ ................... 42 4.3.1 Phosphate Free Synthetic A ged U r ine M ixtures ................................ ...... 42 4.3.2 Stock Phosphate S olution ................................ ................................ ....... 43 4.3.3 Phosphate Dosing E xperiments ................................ .............................. 43 4.4 Analytical Methods ................................ ................................ ............................ 43 5 R ESULTS ................................ ................................ ................................ .................. 48

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7 5.1 Ion Exchange Experiments using Fresh Urine ................................ .................. 48 5.2 Precipitation Experiments in Simulated Hydrolyzed Urine ................................ 48 5.2.1 Concentrations of Calcium and Magnesium A dded ................................ 48 5.2.2 Precipitat ion of Calcium, Magnesium, and P hosphate ............................ 48 5.2.3 Mass of P recipitate ................................ ................................ .................. 49 5.3 Phosphate Dosing Precipitation Experiments ................................ ................... 49 6 D ISCUSSION ................................ ................................ ................................ ............ 55 6.1 Accuracy and Comparison of Ion Chromatography (IC) and T itration Measuring Techniques ................................ ................................ ..................... 55 6.2 Calcium and Magnesium Cation Exchange Isotherms in Fresh Urine .............. 55 6.3 Struvite and HAP Satu ration Index Calculations ................................ ............... 56 6.4 Precipitation Reduction in Cation Exchange Treated Urine .............................. 57 6.5 Mass of Struvite and HAP Precip itates ................................ ............................. 58 6.6 Comparison of Calculated and Measured Phosphate Values ........................... 60 6.7 Measured Mass vs. Theoretical Mass ................................ ............................... 61 6.8 Comparison of Measured and Calculated Precipitation Results to Modeled Results ................................ ................................ ................................ ............. 62 7 CONCLUSIONS AND FUTURE WORK ................................ ................................ .... 70 APPENDIX LIST OF REFERENCES ................................ ................................ ............................... 72 BIOGRAPHICAL SKETCH ................................ ................................ ............................ 77

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8 LIST OF TABLES Table page 2 1 Overview of laboratory struvite precipitation experiments in the literature .......... 31 2 2 Overview of results in the literature of real life urine sepa rating systems and efficiencies ................................ ................................ ................................ .......... 36 4 1 Chemical concentrations in fresh human urine (Udert et al, 2003) and the final synthetic fresh urine mixture ................................ ................................ ....... 46 4 2 Chemical composition of calcium and magnesium free simulated hydrolyzed urine ................................ ................................ ................................ ................... 47 4 3 Chemical composition of synthetic phosphate free simulated hydrolyzed urine sol utions ................................ ................................ ................................ .... 47 5 1 Amount of calcium and magnesium added to samples to represent treatment at various CER doses ................................ ................................ ......................... 54 5 2 Mass of dried precipitate collected after filtration of samples ............................. 54

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9 LIST OF FIGURES Figure page 1 1 Schematic showing organization of thesis. ................................ ......................... 16 2 1 Different urine separation topics as related to the environment, process engineering and the user. Schematic to show factors affecting these three aspects in both conventional wastewater treatment and the proposed urine separation scheme. ................................ ................................ ............................ 30 4 1 Overview of lab experiments, main research questions and studied parameters. ................................ ................................ ................................ ........ 45 4 2 Pro cess schematic for precipitation experiments using synthetic aged urine. .... 46 5 1 Jar test results showing magnesium concentration as a function of resin dose for both detection methods (C 0 = 3. 85 mmol/L). ................................ ................. 50 5 2 Jar test results showing calcium concentration as a function of resin dose for both detection methods (C 0 = 4.3 mmol/L). ................................ ........................ 50 5 3 Graphs showing amount of calcium, magnesium, and phosphate initially added to each sample and remaining in e ach sample after precipitation Table 5 1 provides description of samples. ................................ ........................ 51 5 4 Graph depicting the decreasing mass of precipitate collected as CER dose increases. ................................ ................................ ................................ ........... 52 5 5 Amount of HAP formed in simulated hydroloyzed urine at specific doses of phosphate w ith and without magnesium present. The vertical line represents the dose of phosphate that satisfies complete struvite precipitation with magnesium. ................................ ................................ ................................ ........ 52 5 6 Amount of struvite formed in fully h ydrolyzed urine at varying phosphate doses with and without calcium present. ................................ ............................ 53 6 1 Isotherm for magnesium and calcium removal as measured by titrations. ......... 64 6 2 Calculated saturation index values for HAP and struvite in hydrolyzed urine for various CER dosages. Table 5 1 gives a description of the samples. ........... 64 6 3 Fract ions of phosphate, magnesium and calcium precipitated in each sample after cation exchange treatment and mixing. ................................ ...................... 65 6 4 Mass fraction of solids expected to form in hydrolyzed urine based on ma gnesium and calcium measurements. ................................ ........................... 65

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10 6 5 Phosphate precipitated in fully hydrolyzed urine as measured by ion chromatography and determined from stoichiometric ratios with measured magnesium an d calcium. ................................ ................................ .................... 66 6 6 Collected and calculated mass of dry precipitates for each CER dose. .............. 66 6 7 Mass fractions of dry solids expec at each CER dose. ................................ ................................ ............................. 67 6 8 Measured and modeled percent of magnesium precipitated in ion exchange treated, simulated hydrolyzed urine. ................................ ................................ ... 67 6 9 Measured and modeled percent of calcium precipitated in ion exchange treated, simulated hydrolyzed urine. ................................ ................................ ... 68 6 10 Measured and modeled pe rcent of phosphate precipitated in ion exchange treated, simulated hydrolyzed urine. ................................ ................................ ... 68 6 11 Measured and modeled concentrations of struvite precipitated in ion exchange treated, simulated hyd rolyzed urine. ................................ .................. 69 6 12 Measured and modeled concentrations of HAP precipitated in ion exchange treated, simulated hydrolyzed urine. ................................ ................................ ... 69

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11 LIST OF ABBREVIATION S ACP Amorphous calcium phosphate Ca/Ca 2+ Calcium CaCO 3 Calcium carbonate CER Cation exchange resin CSO Combined sewer overflow DI Deionized EDTA Ethylenediaminetetraacetic acid g Gram or grams HAP Hydroxyapatite HCO 3 Bicarbonate I Ionic strength IAP Ion activity product IC Ion chromatograph or ion chromatography IX Ion exchange K Potassium KMP Potassium ammonium phosphate L Liter or Liters Mg/Mg 2+ Magnesium mg milligram min Minute or minutes mL Milliliter or milliliters M Molar MAP Magnesium ammonium pho sphate

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12 mM Millimolar N Nitrogen NH 3 /NH 4 + Ammonia/ammonium OCP Octacalcium phosphate OH Hydroxide P Phosphorus PO 4 /PO 4 2 Phosphate SI Saturation index SO 4 2 Sulfate m Micrometer L Microliter WWTP Wastewater treatment plant

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13 Abstract of Thesis Present ed to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Engineering URINE SOURCE SEPARATION : CRITICAL LITERATURE REVIEW AND NOVEL PRECIPITATION CONTROL By Kyle Taylor December 2011 Chair: Treavor Boyer Major: Environmental Engineering Urine separation and treatment can provide many benefits, including nutrient recovery, reduced water and resource use, and lower capacity wastewater treatment plants. The environmental benefits are numerous but success of these systems depend s greatly on process engineering and user acceptance Laboratory scale studies have sought to optimize the recovery of a potentially valuable mineral, struvite, a magnesium phosphate mineral, from u r ine by precipitation. Few full scale reactors for struvite precipitation have been implemented at this time These units have shown good recovery of phosphorus but more research is need ed to make them economically feasible and ensure maximum nutrient recov ery Urine separating units are hindered by clogging due to mineral precipitation triggered by urea hydrolysis, a process catalyzed by the enzyme urease which transforms the urea into ammonia and bicarbonate. The two most common mineral precipitates are h ydroxyapatite (HAP), a calcium phosphate mineral, and struvite. P roblematic precipitation, along with other usability issues, ha s resulted in variable success of urine separation units.

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14 Preliminary experiments were conducted to examine the removal of mag nesium and calcium from synthetic urine using a cation exchange resin with the goal of preventing the formation of HAP and struvite. Cation exchange treatment showed good removal of both calcium and magnesium from the urine, with a preference for calcium. However, calculations showed that HAP and struvite were still supersaturated in the treated urine, which motivated subsequent precipitation studies. The goal of the precipitation studies was to study the rate and extent of mineral precipitation. A syntheti c urine mixture was prepared to simulate urine after it had undergone cation exchange treatment and urea hydrolysis. Two batches of synthetic hydrolyzed urine were made: magnesium only and calcium only. The aged urine was dosed with different amounts of ph osphate to observe the amount of calcium and magnesium precipitated from the urine. Results from the precipitation studies agreed with the stoichiometry for struvite precipitation (1:1 Mg:P) and HAP precipitation (5:3 Ca:P). This research is important beca use it provides new information about precipitation reactions in urine which is expected to improve the performance of waterless urinals and urine source separation technology

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15 CHAPTER 1 OVERVIEW OF THESIS The overarching goal of this thesis wa s to systematically evaluate source separation and treatment of human urine by conducting a comprehensive review of the literature and conducting laboratory experiments. The literature review focused on environmental benefits, process engineering advances and challenges, and user attitudes and real life efficiency. The laboratory experiments focused on mineral precipitation in urine, which remains a major obstacle to urine separation and treatment. Figure 1 1 shows the organization of thesis. Chapter 2 is t he literature review. Chapters 3 6 present results from the laboratory research. Chapter 7 provides conclusions that span the literature review and laboratory research, and provides reco mmendations for future research

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16 Figure 1 1. Schematic showing orga nization of thesis

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17 CHAPTER 2 CRITICAL LITERATURE REVIEW 2.1 Overview and Objectives Source separation and treatment of human urine has many advantages over the conventional approach to domestic wastewater treatment. At the highest level, urine separatio n and treatment can drastically reduce the load of nutrients to wastewater treatment plants, thereby saving energy and increasing the efficiency of treatment units. Nutrients that are currently discharged to the environment, from either incomplete treatmen t or leaks in the system, would be eliminated by separate collection and treatment of urine. Urine separation and treatment offers the possibility of recovering nutrients from urine for beneficial use, which is attracting increasing interest as mineral res ources such as phosphate are becoming scarce and require increasing energy inputs for production. Unfortunately, there is not a clear consensus on the most effective collection and treatment scheme for urine separation and treatment. As a result, widesprea d implementation of urine separation and treatment is far from reality at current conditions. The environmental benefits of urine separation and treatment cannot be fully realized without reliance on innovative process engineering to overcome issues with i mplementation and user de pendent success rates. Figure 2 1 illustrates the intersection of the environment, process engineering, and user in the context of conventional wastewater treatment and innovative urine separation and treatment. This goal of the l iterature review was to provide new insight on a few aspects on the current states of urine separation and treatment. The environmental benefits and contributions to sustainable wastewater management are the key drivers for urine separation and treatment. However, many obstacles remain that hinder the realization

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18 of urine separation such that innovative process engineering approaches are needed. Previous research on urine separation and treatment is vast with numerous attempts to optimize different processe s for urine treatment. Struvite precipitation is the most widely studied process in urine treatment because of its potential to recover multiple nutrients from urine. As such, struvite precipitation was the focus of the process engineering section of the l iterature review. Finally, user dependent success was examined by reviewing the success of past urine separation projects and by looking at impediments to success ful urine separation, specifically spontaneous precipitation 2.2 Environment The current appr oach to centralized municipal wastewater treatment consumes large amounts of freshwater, discharges nutrients to water bodies, does not properly remove potentially toxic endocrine disrupting chemicals and micropollutants (Larsen et al. 2001) and allows n o option for resource recovery. The idea behind urine separation and treatment is that treating concentrated, unmixed solutions is more resource efficient then treating highly dilute combined solutions (Larsen and Gujer 1997) Currently, NoMix toilets dev eloped at the Swiss Federal Institute for Environmental Science and Technology provide an easy, effective way to separate urine and save about 80% of the water used in toilet flushing (Larsen et al. 2001) Waterless urinals can also be used to separate ur ine. Urine contains over 80% of nitrogen, 50% of phosphorus, 90% of potassium in the total nutrient load to conventional wastewater treatment plants (Larsen et al. 2001) The removal of the nutrient load on wastewater treatment plants by separation and tr eatment of urine could provide many benefits. By removing urine before sending wastewater to the plant, influent carbon and nitrogen levels in the remaining wastewater

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19 would be ideal for removal of organic material and nitrogen by biological treatment (Lar sen et al. 2001) Separation of urine can also reduce the toxic effects of combined sewer overflow s that discharge into rivers and lakes (Larsen et al., 2001) Leaks from the wastewater collection system introduce pollutants to the environment and threate n groundwater quality (Larsen and Gujer 2001) separation of urine, which contains 70 80% of pharmaceuticals in these sewers, reduc es this risk (Larsen and Gujer 2001) Nutrient treatment and release by traditional wastewater treatment plants also elimi nates the option of significant nutrient recovery and reuse. Limited phosphorus resources and energy intensive nitrogen fixation are important drivers for nutrient recovery and reuse (Cordell et al., 2009; Larsen and Gujer, 2001; Hanaeus et al. 1997) Rec overy of the nutrients in source separate urine could potentially eliminate the environmental impacts associated with the production of synthetic fertilizers and resource depletion (Larsen et al. 2001) Urine separating systems have been used in Sweden fo r sustainable waste treatment and nutrient recycling since the 1990s (Hanaeus et al. 1997) The original urine separation systems used a toilet, much like a conventional toilet, but with a small unit for urine collection and a flush water system for this unit, the pipes lead to a storage tank that stored the urine for a period of eight months maximum and then urine was directly applied to the local grazing fields (Hanaeus et al. 1997) Since their inception these units have been modified to increase usabi lity and nutrient separation and collection. Real world efficiency of both early source separating toilets and current models are discussed in section 2.4. 2.3 Process Engineering The concept of urine source separation is very appealing for the reasons des cribed in the previous section. However, considerable development is needed to

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20 fulfill the promises of urine source separation and treatment. Moreover, whether current technology will actually become a viable and economically attractive alternative to conv entional wastewater treatment will depend greatly on technical improvements to applicable solutions (Larsen et al. 2010) Research is needed to determine both technical aspects of urine separation but also how it will be implemented into the existing infr astructure (Berndtsson 2006) Planning of the separation, collection, storage, and transportation aspects of urine source separation have been suggested. Early literature on source separation proposed storage of urine and conveyance to the wastewater tre atment plant in waves, in order to create a smooth, even load of nutrients thereby reducing changes of harmful emissions to the environment (Larsen and Gujer, 1996; Larsen et al. 2009) However, current thinking is focused on decentralized, or onsite trea tment as a more practical and economically feasible option. Technical progress and research can help develop these on site technologies (Larsen et al. 2009) Many different options have been studied, but not many technologies have made it beyond laborator y scale testing. Different combinations of current process can achieve different goals but there has yet to be a consensus on what combination of these technologies will be the most beneficial and feasible. 2.3.1 Laboratory scale struvite precipitation res earch Though direct application of urine to agriculture is the simplest, most obvious choice of nutrient reuse from urine, there are concerns about micropollutants and pathogens in urine that may have associated ecotoxicological risks (Larsen and Gujer 20 01) There is also concern that urine can increase the salinity of soils thereby decreasing soil fertility (Mnkeni et al., 2008; Karak and Bhattacharyya, 2011) In

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21 addition, the concentration of nutrients in urine is lower than commercial fertilizers; as a result transportation of large volumes of untreated urine would be required a t a considerable economic cost ( Maurer et al., 2006; Pronk and Kone 2009). As a result, treatment processes that can recover the nutrients in urine at a high concentration can e liminate many of the transportation issues as well as the risks associated with pathogens micropollutants and salinity Successful treatment of source separated urine must also overcome the instability of urea, which upon hydrolysis, increase urine pH an d results in ammonia loss and unpleasant odors (Larsen and Gujer 1996) Hydrolysis of urea can also lead to precipitation that can hinder the usability of collection units and the success of subsequent treatment ( see section 2.4 for a more information on urea hydrolysis ) Options being considered for separate urine treatment include volume reduction using evaporation or freeze thawing, removal of micropollutants by electrodialysis, and hygieni z ation through storage, among many other processes (Maurer et al 2006) Recent research has suggested that precipitation and collection of struvite, a magnesium phosphate mineral (NH 4 MgPO 4 6H 2 O), from source separated urine is an effective treatment technique (Lar sen and Gujer, 1996; Lind et al., 2000; Maurer et al., 2006 ) Struvite could be used as a valuable source of fertilizer, and nearly close the cycle for phosphorus, which is known to become scare in the foreseeable future. Struvite precipitation is an attractive treatment for source separated urine as it conta ins two dominant nutrients nitrogen and phosphorus, in solid form (Maurer et al. 2006) and it has shown potential to be us ed as a slow release fertilizer (Bridger et al., 1962; El Diwani et al., 2007; Johnston and Richards 2003) Additionally, the pH of completely

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22 hydrolyzed urine, of pH 9 and above (Udert et al. 2003) is ideal for struvite precipitation (Buchanan et al. 1994) W ithout the addition of magnesium, however, only about 27% of the phosphorus and 0.6% of the nitrogen found in urine will pre cipitate as struvite (Udert et al. 2003) This has led to a plethora of research into the optimum conditions, including magnesium addition, pH adjustment, phosphorus addition (for increased nitrogen removal), and dilution factors for struvite recovery fro m source separated urine. Additionally, recent studies have examined the option of co precipitation of potassium struvite. It can be concluded from Table 2 1 that at a magnesium to phosphorus ratio (Mg:P) of 1.5:1 in hydrolyzed urine, over 90% of phosphoru s can be recovered as struvite regardless of pH. For unhydrolyzed, pH adjusted urine, the trend is less clear. 2.3.2 Implementation of struvite precipitation reactors Though struvite precipitation technologies have been used to recover struvite from vario us waste streams, including anaerobic digester supernatant, chlorinated secondary effluents, swine wastewater, and liquors ( (Le Corre et al. 2009) for a comprehensive review), few have been attempted with urine outside of the laboratory. Two reports of fu ll scale, struvite crystallization from source separated urine have been tested as described below. Antonini et al. ( 2008) studied the effectiveness of a struvite precipitation reactor, NuRec, using urine collected from one urine separating toilet and 1 wa terless urinal in a dormitory of 100 students. The NuRec system used magnesium oxide dosed at a magnesium to phosphorus rat io of 1.5:1; about 50 L of stored urine was treated at a time. Thirty minutes of mixing was followed by a 3 h sedimentation phase. Th e effluent was treated by stripping and absorption processes. The authors tested both diluted and

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23 undiluted urine, containing phosphorus concentrations of 2.30 mg/L to 110.83 mg/L and 5.20 mg/L to 311.2 mg/L, respectively. For undiluted urine, about 100 g struvite could be recovered per batch, while only 32 g could be collected in diluted urine. Between 10 30 g of the struvite precipitate was lost during recovery as it remained trapped in the filter fibers. F or diluted urine this translated to a loss of 91. 5% of precipitat ion struvite, making the process unproductive Etter et al. ( 2011) studied the functionality of precipitating struvite from urine using a filtration reactor in a village in Nepal. The urine was collected using urine diverting dry toilets an d had been stored and slightly diluted (due to cleaning of the toilets) before experimentation. Etter et al. (2011) used three different magnesium sources, magnesium sul f ate, bittern (a waste stream from salt production) and magnesium rock. The reactor wa s made from sheet metal and consisted of a 50 L drum with a conical bottom, with a welded stirring mechanism that led to a filter bag through a ball valve. The filter chosen was nylon with a pore size of 160 m. Struvite was precipitated from additio n of magnesium in a magnesium to phosphorus molar ratio of 1.1 :1 and 10 min of stirring; after which, the retained filter cake was dried. The reactor was able to removed 91% of the phosphate content of the urine. The time to process 50 L of urine took about 1 h and due to this low retention time struvite scaling on the reactor walls was not an issue. Etter et al. (2011) estimated that 1 kg of struvite could be recovered from 720 L urine at a 1:1 molar magnesium to phosphorus dosage. The value of the effluent fr om the reactor, due to its high nitrogen and potassium concentration has an estimated value of four times that of the struvite. Etter et al. (2011) suggests that direct application would be the easiest way through drip irrigation

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24 systems, protecting from ammonia loss due to volatilization. However, direct application feasibility is limited and additional physical, chemical, or biological process could be necessary for effluent treatment. Both studies showed some success in recovery of struvite from undilut ed urine, but improvements could be made to increase recovery. Effluent from the reactors required treatment, but could be used beneficially as fertilizer, as it contained high potassium and nitrogen levels. 2.4 User The key for long term success of urine separation and treatment is user acceptance and attitudes toward the system. An increase in user motivation can be seen when users are supplied with knowledge regarding the benefits of urine separation (Berndtsson 2006) User compliance and acceptance can also be increased with development and implementation of effective collection units. Collection units need to be easy to use, as user acceptance is a prerequisite for widespread use (Lienert and Larsen 2010) This means overcoming many obstacles that cur rently detract u sers from urine separating units, including odors, maintenance issues due predominantly to clogging and behavior modification. 2.4.1 Usability issues and problematic precipitation Mineral precipitation in traps and pipes are the major cau se of odor and blockages in urine collection systems ( Hanaeus et al., 1997 ; Udert et al., 2003; Udert 2003c ; Larsen et al., 2009 ) The two minerals most commonly found in NoMix toilets and waterless urinals are struvite and hydroxyapatite (HAP) (Udert et al. 2003) HAP is a calcium phosphate mineral, Ca 5 (PO 4 ) 3 (OH). The enzyme urease, which are abundant in urine collecting systems, induces a process known as urea hydrolysis (or ureolysis) in

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25 which the urea in urine is decomposed into bicarbonate and ammon ium and triggers an increase in pH (Udert et al. 2003) The urea hydrolysis reaction can be written as: NH 2 (CO)NH 2 + 2H 2 3 + NH 4 + + HCO 3 (2 1) The increase in pH and ammonium concentration results in the formation of struvite and HAP. Complete urea hydrolysis can be achieved in a little more than 1 day in urine collecting systems containing urease (Udert 2003c) but only about 2.5% and 20% of ureolysis is necessary to reach the saturation limit fo r struvite and HAP, respectively (Udert, 2003b; Udert et al. 2003) In a few hours of storage, undiluted urine can spontaneously precipitate nearly all of its calcium and magnesium and about 27% of the phosphate (Udert 2003c) N ot all of th e precipitatio n takes place in the collection system but also occurs in the pipes and traps of the system, which causes blockages and odor problems. Importantly, t he precipitation of these nutrients before reaching the urine collecting system also reduces their availabi lity for later recovery and use as fertilizer (Udert et al. 2003) Several options have been suggested to reduce the precipitation of HAP and struvite in the plumbing of urine separating toilets and waterless urinals. Periodic cleaning with caustic soda o r a mechanical snake (Jonsson 2002) to clear blockages is effective, but may not be suitable for high use or public units. Preventing urea decomposition with sul f uric acid (Hellstrom et al. 1999) and urease inhibitors in urine storage has been examined. Self cleaning surfaces to prevent biofilm build up and subsequent biological activity is another option for precipitation prevention ( Barthlott and Neinhuis, 1997; Moriyama et al., 1998; Li et al., 2007 ) Alternatively, forced precipitation in removable t raps which can be exchange and cleaned periodically can be another way

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26 of preventing blockages (Udert et al. 2003) however it may be a challenge to develop a device small enough to be integrated into the toilet and allow for good interface between user a nd technology (Larsen et al. 2009) Removal of magnesium and calcium from urine prior to entering the urine plumbing system has the potential to reduce odors and blockage and assist with the controlled production of struvite. Without magnesium and calcium less phosphorus will be bound in spontaneous precipitation and allow for more struvite formation per volume of urine, increasing the desired product and nitrogen removal. Furthermore, removing calcium preferentially to magnesium will increase the magnesi um to calcium ratio above 0.9, which is necessary for guaranteed struvite formation (Abbona et al. 1986). Tilley et al. ( 2008) showed that precipitation work done on post spontaneous precipitation urine (i.e., only 15% of the original calcium and magnesiu m found in urine) was ideal for magnesium dosing and production of 99.5% calcium free struvite. Etter et al. ( 2011) estimated that 40% more struvite could be collected in a urine treatment unit if spontaneous precipitation was prevented. 2.4.2 Overview of real life systems The most widely used source separation technologies are NoMix toilets and waterless urinals. These units are designed to provide low dilution of the urine and show comparable functionality to standard flush toilets and urinals. Ideally, t hese units would be able to collect 80% of the nitrogen and 50% of the phosphorus load of wastewater treatment plants, however nutrient collection in real life systems is far from ideal. Many researchers have studied these factors in urine separation and n utrient collection efficiency. Hanaeus et al. ( 1997) monitored the efficiency of nutrient collection in a urine separation system in a village in Sweden. The 55 person village collected the urine into

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27 three storage tanks for later reuse as fertilizer by di rect application. The nutrients collected during the study period can be seen in Table 2 2; the authors estimated that the system collected between 2.8 3.7 g total nitrogen and 0.16 0.18 g total phosphorus per person per day, which assuming that 70% of toi let visits occur at home, indicates urine separation efficiency between 50 60%. In the storage tanks urine ha s a high pH and 85 90% of the nitrogen appeared as ammonia, which indicates the potential loss of nitrogen through ammonia volatilization. Loss of nutrients was also attributed to the contamination of the urine collecting unit with flush water from the solid waste portion, along with leakages of water into the urine collecting system. Rossi et al. ( 2009) studied the efficiency of urine separation in four apartments equipped with NoMix toilets for one year. The NoMix units had a separate urine collecting unit, which upon flushing, closed to prevent dilution. The toilets had two flush levels of 3 and 6 L of water for the back portion of the toilet. They also reported the whose urine outlet received 8 mL of flush water, and a waterless urinal. The authors measured the collection of about 138 mL of urine/flush in the apartme nts, and 225 reported nutrients collect ed can be seen in Table 2 2 The authors reported a low amount of urine collection per use when compared to expected urine volume; they attributed this to flaws in the measurement of toilet uses as they can be used for other restroom had better urine collection due to the fact that 76% of the men visited the wat erless urinal, in which close to no urine is lost. A low nitrogen to phosphorus ratio

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28 suggests nitrogen losses in the urine conducting pipes The authors estimate that urine recovery in household to be between 70 75% of expected quantity, leaving room for technical and behavior improvements. Vinners and Jnsson ( 2002) studied the efficiency of a system that included both urine and feces diversion. The study used Dubbletten urine diverting toilets. The system uses two, well separated bowls and two flushing systems that are independent of one another. The large bowl, for feces, has a bulge which prevents an overflow of the flushing water into the front urine bowl. The authors studied 35 people for a period of 35 days. It was determined that 68% of the urine was collected, with the remaining fraction falling into the rear bowl. The collected and measured nutrients values were extrapolated to give an estimation of possible nutrient recovery from one person per year, which can be seen in Table 2 2. In another st udy by Jonsson e t al. ( 1997) using early urine separating toilets, the authors found no evidence of ammonia loss through ventilation and a nitrogen to phosphorus molar ratio of 11.6:1. In the storage tank 86, 81 and 104% of the expected amount of nitrogen phosphorus and potassium, respectively, were collected. The discrepancies in nitrogen and phosphorus are explained by a small amount of urine falling into the rear bowl and a high percentage of vegetarians. In this study, only 0.34 L of water per inhabit ant and day were used, keeping the solution dilute and cut water consumption in half, compared to conventional toilets. If the urine separating units are hard to use and require a large effort by the user, nutrient separation drops (Jonsson 2002) Many us ers were detracted from the need to sit while urinating ( Jonsson, 2002; Rossi et al., 2009 ) which is a necessity on many

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29 NoMix units. Each of the studies reported various technical problems with the urine collecting units or piping but one consistent conc lusion was that success was dependent upon user motivation and dedication.

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30 Figure 2 1 Different urine separation topics as related to the environment, process engineering and the user. Schematic to show factors affecting these three aspects in both c onventional wastewater treatment and the proposed urine separation scheme

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31 Table 2 1. Overview of laboratory struvite precipitation experiments in the literature Source Aged? Precipitation method pH adjustment P removal/recovery P removed as N/K remova l/recovery Mixing Conditions Other/notes (Wilsenach et al., 2007a) Synthetic urine + additional P Yes, with urease addition Addition of MgO / MgCl 2 for Mg:P = 1 Constant pH of 9.4 due to urease 99% P removal MAP Stirred and unstirred Mg:P = 0.75 Synthetic urine no urea and low NH 4 Cl (40mg/L N) No, represented post nitrification denitrification of urine Addition of MgCl 2 for Mg:P =0.5:1 None KMP Mg:P = 1:1 Mg:P = 1.5:1 oval Addition of MgO for Mg:P =0.5:1 Mg:P= 1:1 100 % P removal (Liu et al., 2008) Real human urine Yes, mixed for 15 days Addition of MgCL 2 for Mg:P 1.0:1 none 85% P recovered MAP 3.7% N recovered G= 150, 2 hours mi xi n g N/P constant at 84.3:1 1.3:1 95.7% P recovered 5.9% N recovered 1.5:1 97.9% P recovered 5.3% N recovered Addition of MgCL 2 and Na 2 HPO 4 for Mg:N:P of 1.2:1:1 pH of 8.5 with NaOH 85.1% P recovered MAP 95.7% N recovered 1.3:1 :11 94.1% P recovered MAP 95.1% N recovered (Kabdasli et al. 2006b) Real human urine No MgCl 2 and NaH 2 PO 4 to dose to Mg:N:P 1:1:1 Yes, NaOH and H 2 SO 4 to pH= 7.5 89% P removal MAP 22.5% removal NH 3 Yes, slow mixing for 48 hours pH= 8 90.75% rem oval 41.2% removal NH 3 % pH = 8.5 97.66% removal 46% removal NH 3 pH= 9 98.9% removal 48 removal NH 3 pH = 9.5 99.3% removal 51.9% removal NH 3

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32 Table 2 1. Continued Source Aged? Precipitation method pH adjustment P removal/recove ry P removed as N/K removal/recovery Mixing Conditions Other/notes (Ronteltap et al. 2007) Real human urine Yes, naturally in urine collecting unit MgCl 2 for apx PO 4 P:Mg of 1:1.5 No 100% removal of PO4 P MAP Yes, stirred for 3 hours >98% hormones and p harmaceuticals in solution, and 20 63% of added heavy metals precipitated with struvite (Ronteltap et al. 2010) Real human urine Yes, in storage tank MgCl 2 for ratio of P:Mg of 1:1.5 Yes, with NaOH /HCl For pH=7 92.2% removal MAP Yes, 75 mins Average crystal size= 74 m pH=7.5 94.1% removal 126 m pH= 8 97.3% removal 136 m pH= 8.5 98.4% removal 121 m pH=9 99.4% removal 92 m pH=10 99.4% removal 90 m pH=11 99.5% removal 129 m (Kemacheevakul et al. 2 011) Real human urine No pH induced; initial of urine Mg/P <1 NaOH/ H 2 SO 4 pH= 9 26.19% recovery MAP 200 rpm, 1 min, and 20 rpm for 20 mins pH= 10 29.04% recovery pH= 11 31.06% recovery (Tilley et al. 2008) Synthetic urine Yes with urease Dosed with PO 4 : Mg ratio of 1:1 or 1:2 pH above 8 Between 80 93% P in struvite, no real trend with ratios Shaken for 1 minute, reacting for 1 hour Spontanteous precip filtered out, dilutions also examined (Lind et al. 2000) Synthetic urine No Do sed with MgO for Mg:P of 1:9.72 None 100% P removal Struvite, written as [(Ca,Mg)(K,NH4) (PO4)6H2O] 22% K removal 2% Ca removal 1:3.24 100% P removal 35% K removal 3% Ca removal 1:1.62 100% P removal 64% K removal 5.6% Ca removal

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33 Table 2 1. Continued Source Aged? Precipitation method pH adjustment P removal/recovery P removed as N/K removal/recovery Mixing Conditions Other/notes (Xu et al., 2011) Synthetic uri ne Yes; removal of ammonium /carbonate Dosed with Na 2 HPO 4 and MgCl 2 for M g:K:P ratio of 1.6:1:1.6 NaOH for pH adjustment to : MPP 200 rpm for 20 minutes mixing time and 20 minutes sedimentation time pH = 7 pH = 8 pH = 9 moval pH = 10 pH = 11 pH = 12 1.6:1:2 Yes, pH adjusted to 10 with NaOH 2:1:2 76% K removal 2.5:1:2 100% P removal 2:1:1.6 removal 2:1:2.5 Yes; removal of carbonate plus 40 mg/L NH 4 N Dosed with Na 2 HPO 4 and MgCl 2 for Mg:K:P ratio of 2:1 :2 Yes, pH adjusted to 10 with NaOH 4 removal 100 mg/L NH 4 N removal 4 removal 300 mg/L NH 4 N removal 4 removal 500 mg/L NH 4 N removal 4 removal (Darn et al. 2006) Human Urine No pH adjustment 27% of P in solids at pH 8 10 MAP none (Basakcilardan Kabakci et al. 2007) Human Urine No Mg: P = 1:1 pH = 9 94.3% P removal MAP plus calcium precipitates 35% NH 3 N re moval 1600 min 1 for 30 minutes pH = 9 95% P removal 37.5% NH 3 N removal 1600 min 1 for 60 minutes pH = 9 96% P removal 40% NH 3 N removal 1600 min 1 for 120 minutes pH= 10 96.2% P removal 38% NH 3 N removal 1600 min 1 for 30 minutes pH = 10 97.3% P removal 40.2% NH 3 N removal 1600 min 1 for 60 minutes pH = 10 97.5% P removal 42% NH 3 N removal 1600 min 1 for 120 minutes

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34 Table 2 1 Continued Source Aged? Precipitation method pH adjustment P removal/recovery P removed as N/K removal/recovery Mixing Conditions Other/notes (Basakcilardan Kabakci et al., 2007) Human Urine No Mg:P = 0.4:1 pH = 9 68.7% PO 4 P removal 3 N removal 1600 min 1 for 60 minutes removal pH = 9.5 4 P removal 3 N removal removal pH = 10 4 P removal 3 N removal removal pH = 10.7 97% PO 4 P removal 3 N removal removal Human Urine No Mg:P = 1.3:1 pH = 9 4 P removal 3 N removal 60.7 % Ca removal pH = 9.5 4 P removal 3 N removal removal pH = 10 4 P removal 3 N removal removal pH = 10.7 4 P removal 3 N removal 71.9 % Ca removal Human Ur ine No Mg:P = 0.4:1 pH = 9 4 P removal 3 N removal removal Mg:P = 0.6:1 4 P removal 3 N removal removal Mg:P = 0.65:1 4 P removal 3 N removal removal Mg:P = 0.85:1 4 P removal 3 N removal removal Mg:P = 1:1 4 P removal 3 N removal removal Mg:P = 1.2:1 4 P removal 3 N removal removal Mg:P = 1.3:1 O 4 P removal 3 N removal removal Mg:P = 1.57:1 96% PO 4 P removal 52.5% NH 3 N removal 66 % Ca removal

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35 Table 2 1. C ontinued Source Aged? Precipitation method pH adjustment P removal/recovery P removed as N/K removal/recovery M ixing Conditions Other/notes (Basakcilardan Kabakci et al. 2007) Human Urine No Mg:P = 1.8:1 4 P removal 3 N removal removal Dosed with Na 2 HPO 4 and MgCl 2 for Mg:P:N of 1.1:1.1:1 Adjusted with NaOH for pH=8 87.8% P remova l Mostly pure MAP. Approximately 0.12% and 0.33% Ca and K in solids 94.7% N removal 120 r/min 1.3:1:1 pH= 9.5 99.8% P removal 91.3% N removal 60 r/min 1.3:1.1:1 pH= 8.5 99.8% P removal 98.4% N removal 120 r/min 1.1:1:1 pH= 10 99.8% P remov al 93.9% N removal 60 r/min 1.2:1:1 pH= 8 99.9% P removal 92.4% N removal 120 r/min 1:1.1:1 pH= 9.5 77.6% P removal 91.4% N removal 60 r/min 1:1:1 pH= 8.5 79.5% P removal 88.7% N removal 120 r/min 1.2:1.1:1 pH= 10 99.8% P removal 9 6.9% N removal 60 r/min 1:1.15:1 pH= 8 70.7% P removal 89.0% N removal 60 r/min 1.2:1.05:1 pH= 9.5 99.9% P removal 96.6% N removal 120 r/min 1.2:1.15:1 pH= 8.5 98.2% P removal 99.0% N removal 60 r/min 1:1.05:1 pH=10 79.4% P removal 90.2% N removal 120 r/min 1.3:1.05:1 pH= 8 99.8% P removal 93.2% N removal 60 r/min 1.1:1.15:1 pH= 9.5 79.7% P removal 96.2% N removal 120 r/min 1.1:1.05:1 pH= 8.5 92.6% P removal 95.5% N removal 60 r/min 1.3:1.15:1 pH= 10 99.9% P re moval 98.8% N removal 120 r/min

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36 Table 2 2. Overview of results in the literature of real life urine separating systems and efficiencies Population System/Piping Tank Nutrients Collected/Percent of expected Separation /Recovery Efficiency Issues Reu se (Hanaeus et al. 1997) 55 60% adults Urine separating toilets, PVC pipes, 1800m of pipe to storage tank 3 tanks, 10m3, 5m3, and 10m3 Tot N g/L tank a/b/c= 0.54,2..84,1.38; NH4 N g/l 0.46,2.51,1.17 Tot P: 0.031,0.169, 0.066 50 60% separation and 50% collected and transported High dilution from flush water seep into urine section; leakage into urine sewer system Direct app to field (Rossi et al. 2009) 10 people, 4 apartments, 1 child and NoMix plus waterless urinals 200 L storage tank Household: NH 4 gm 3 : 1905 Ngm 3 : 2259 PO 4 gm 3A : 387 TotP gm 3 : 430 NH 4 gm 3 : 5027 PO 4 gm 3 : 232 Women;s: NH 4 gm 3 : 3795 Ngm 3 : 4590 PO 4 gm 3 : 200 53% of average bladder voiding volume collected in households; 86% in Nitrogen losses in urine pipi ng system (Jonsson 2002) 315 people BB Dubbletten and Worst Man Ecology DS %Urine N collected: BB Dn 61% WM Ds: 65% %Urine P: BB Dn: 59% WM Ds: >65% % Urine K: BB Dn : 75% WM DS:58 Problems with precipitation in u bend Direct a pplication to field (B erndtsson 2006) 125 inhabitants Worstman Ecology DS Two tanks with volumes of 60m 3 and 15m 3 N tot: 313.5 kg/year; 50% of theoretical P tot: 28.5 kg/year; 40% of theoretical User complaints of smell Direct reuse (Jonsson et al. 1997) 44 apartments, 160 persons Separating toilet; front bowl with small spray nozzle Two tanks, 40 m3 N tot mg/l: 3631 Nh3/Nh4 N mg/l: 3576 P tot mg/l: 313 K tot: mg/L: 1000 86% N 81% p 104% K (Vinners and Jnsson 2002) 18 apartments, 34 adults, 1 child Dubbletten urine div erting toilets N : 3741 g/person year P: 340 g/p y K: 1186 g/p y A : PO 4 does not include precipitated amount

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37 CHAPTER 3 LABORATORY RESEARCH GOALS, OBJECTIVES AN D LIMITATIONS The overall goal of this research was to determine whether cation exchange can effectively remove calcium and magnesium from urine and subsequently lower the amount of pipe clogging precipitates formed upon urea hydrolysis. The research was accomplished by completing the following tasks. First, jar tests were used to quantify ma gnesium and calcium removal from fresh synthetic urine at a range of cation exchange resin (CER) doses. Second, experiments with hydrolyzed synthetic urine were used to determine whether the calcium and magnesium removal achieved by CER changed the composi tion and mass of precipitates from that found in previous studies of urine precipitation. This included measuring the concentration of species before and after urine precipitation and tracking the change in precipitation mass. Third, experiments evaluated precipitation in hydrolyzed urine along a range of phosphate dosages. For all experimental ly determined data, laboratory results were compared with modeling results in order to determine the effectiveness of chemical modeling programs for use in urine. Exp eriments with urine often are subject to many limitations that may hinder the effectiveness, reproducibility, and implementation of the results. First, urine is a very concentrated solution with high ionic strength that presents difficulties when using ana lytical instruments and methods generally used on natural waters. Preparation of synthetic urine is also difficult due to spontaneous precipitation and complexation reactions. For instance, the fresh synthetic urine used in this project could not contain p hosphate because of uncontrolled precipitation. Furthermore, the hydrolyzed synthetic

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38 urine containing calcium could not include bicarbonate due to formation of calcium carbonate. Fundamentally, the goal of producing a general synthetic urine recipe is fla wed because of the high variance in urine values found throughout the literature. Urine also contains various organic complexing agents which are difficult to identify and quantify in the literature (Brown et al. 1994) The presence of these complexing ag ents may play a role in precipitation that is unable to be reproduced in the lab. Real life implementation of urine precipitation studies are further limited by the chemical alteration caused in the non sterile environments of urine collecting systems (Mau rer et al. 2006)

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39 CHAPTER 4 MATERIALS AND METHOD S The objectives of the project were carried out in three different experiments referred to as Ion Exchange Experiments using Fresh Urine, Precipitation Experiments in Simulated Hydrolyzed Urine, and Phosp hate Dosing Precipitation Experiments. Below, Figur e 4 1 shows a brief overview of the experiments. 4.1 Ion Exchange Experiments using Fresh Urine 4.1.1 Fresh synthetic urine A synthetic urine was made to contain the constituents found in fresh human urin e as described in (Udert 2003b) A commercial synthetic urine (Ricca Chemical Company) was used as the base solution for the fresh synthetic urine (hereafter Ricca urine) The Ricca urine was a very simpl e mixture and lacked many of the constituents found in fresh human urine and those it did contai n varied in concentration level A number of synthetic urine formulations were made and analyzed in the laboratory The goal was to make the synthetic urine as similar in chemical composition to fresh urine as p ossible with particular focus on matching the magnesium and calcium concentrations. M any of the formulations caused immediate precipitation in the solution. Unwanted precipitation was avoided by not adding phosphate to the synthetic fresh urine The final synthetic fresh urine was prepared by adding NH 4 Cl, (NH 4 ) 2 SO 4 and urea to Ricca urine. A comparison between the constituents and concentrations found in fresh human urine and those contained in the final synthetic fr esh urine can be seen in Table 4 1 The ion concentrations in the urine mixture were checked by both ion

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40 chromatography and titrations, as described in detail below The synthetic urine was filtered and stored in the refrigerator for subsequent use in ion exchange experiments 4.1.2 Resin sele ction and dosing Amberlite 200c cation exchange resin (CER) was used in all ion exchange experiments. Amberlite 200c was chosen due to its strong affinity for calcium and magnesium. Amberlite 200c is a strong acid cation exchange resin with styrene divinyl benzene copolymer matrix and sulfonic acid functional group s (Rohm and Haas, 1999). Sodium is used as the mobile counter ion in the exchange reactions. The initial resin doses and contact time were chosen from previously unpublished data from Dr. esearch group which investigated ion exchange treatment of synthetic urine. It was necessary to have a contact time that allowed the CER to uptake the maximum amount of magnesium and calcium from the urine. The previous data showed that removal potential began to level off around 120 min of contact time. The previous experiment examined resin doses from 2 mL/L to 20 mL/L The desired calcium and magnesium removal was not se en in the 20 mL/L dosed samples. This led to the choice of using a greater range of CER doses that would allow for more calcium and magnesium removal. The final CER doses were 6, 10, 20, 30 and 40 mL/L. Cation exchange r esin doses are given as wet resin volumes, meaning that the dry resin needed to be mixed with deionized (DI) water to m ake a slurry. The resin slurry was then transferred to 10 mL graduated cylinders using disposable plastic droppers until the desired volume of resin was reached. The supernatant liquid in the graduated cylinder was removed from the top of the settled resin T he density of the dry resin was determined by drying and weighing 1 mL of wet resin according to the Standard Method 2540 D. ( total suspended solids dried at 103 105 C) ( Clesceri et al. 2005 )

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41 4.1.3 Batch tests Batch tests were used to quantify calci um and magnesium uptake by CER. One hundred milliliters of the urine was transferred to 250 mL amber glass bottles. The specified dose of CER was placed in a labeled bottle. Each dose was done in triplicate. The bottles were then transferred to a shaker ta ble which was set to 275 rpm for 120 min. Each sample was then filtered to remove all the resin and any particulate matter. Due to the high ionic strength of the urine, each sample had to be diluted 10 before analysis. The c alcium and magnesium concentrat ion for each sample were determined by two different analytical techniques as discussed in section 4.4. 4.2 Precipitation Experiments in Simulated Hydrolyzed Urine 4.2.1 Calcium and magnesium free aged urine A synthetic urine mixture was prepared to rep resent aged urine, or urine that has undergone urea hydrolysis. The aged urine mixture was modeled after values found in the literature for aged human urine. The synthetic aged urine was prepared by adding Na 2 SO 4 KCl, NH 4 Cl, NH 4 HCO 3 NaCl, NH 4 OH, and NaH 2 PO 4 to DI water. The final constituents were modeled after (Udert 2003a) and can be seen below in Table 4 2 Since the experiments varied the calcium and magnesium concentration, the synthetic aged urine did not include either constituent. 4.2.2 Magnesium and calcium stock solutions Two stock solutions were made in order to dose the urine with magnesium and calcium. The magnesium solution was made using MgCl 2 6H 2 O and was 0.1 M in strength. The calcium solution was also made to a strength of 0.1 M and was prepared with CaCl 2 2H 2 O. Both solutions were prepared in DI water and filtered prior to use.

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42 4.2.3 Precipitation experiments The synthetic aged urine mixture was measured into Erlenmeyer flasks on a stir plate and allowed to reach laboratory temperature b efore beginning the experiment. Each flask received a measured amount of both the magnesium and calcium stock solutions. The amount each sample received reflected the amount of magnesium and calcium tha t remained in solution after ion exchange treatment. T here was a sample for each dose of CER used in the fresh urine ion exchange experiments and one blank. Each dose was done in duplicate. The calcium and magnesium solutions were added at approximately the same time. After these additions, the urine was mixe d on medium high speed for 15 min, to allow for the added magnesium and calcium to form precipitates with the phosphate contained in the aged urine mixture. This time was chosen based on previous research that found almost complete precipitation phosphate minerals in 15 min (Ronteltap et al. 2007) When the mixing was completed, each sample was filtered to remove any solids that had precipitated. The solids that were captured on the filter were dried and weighed according to Standard Method 2540 D. (tota l suspended solids dried at 103 105 C) ( Clesceri et al. 2005 ) The filtrate was analyzed for magnesium, calcium, p hosphate, and nitrogen. Figure 4 2 is a schematic showing a detailed overview of the precipitation experiments. 4.3 Phosphate Dosing Precipit ation Experiments 4.3.1 Phosphate free synthetic aged urine mixtures Three phosphate free synthetic urine mixtures were prepared according to (Udert 2003a) with the elimination of phosphate. One was prepared without calcium and the full magnesium concentr ation found in urine (magnesium only). Another contained the full amount of calcium but no magnesium (calcium only). The final mixture contained the

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43 entire amount of magnesium and calcium found in urine. For the two mixtures containing calcium, bicarbonate was not added to prevent immediate precipitation of CaCO 3 The final concentrations of the three phosphate free simulated hydrolyzed urine mixtur es can be seen below in Table 4 3. 4.3.2 Stock phosphate solution A 0.1M stock phosphate solution was prepared using NaH 2 PO 4 in DI water. The solution was filtered prior to use. 4.3.3 Phosphate dosing experiments A set of samples of each of the phosphate free simulated hydrolyzed urines were dosed with varying amounts of the stock phosphate solution. The samples w ere allowed to mix for 15 min, to allow for the precipitation of phosphate minerals. The samples were then filtered to remove all precipitated solids. The filtrate was analyzed for magnesium and calcium. 4.4 Analytical Methods All solutions were prepared u sing ACS grade chemicals and DI water. All filtering was done using a vacuum filter apparatus and 0.45 m nylon membrane filters. Calcium and magnesium were measured by titration for total hardness and calcium hardness. Total hardness was determined by Sta ndard Method 2340 C. (EDTA titrimetric method) ( Clesceri et al. 2005 ) The buffer solution was prepared with ammonium chloride, ammonium hydroxide, and magnesium salt of EDTA and stored in a plastic bottle. The pH adjustment was measured on Acumet AP71 p H meter with a pH/ATC probe The indicator used was a calmagite solution. The standard 0.01 M EDTA titrant was made from reagent grade EDTA and standardized against a standard calcium solution. Analysis for calcium hardness followed Standard Method 3500 Ca B. (EDTA titrimetric

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44 method) ( Clesceri et al. 2005 ) The indicator used was Eriochrome Blue Black R indicator. The pH was adjusted with a sodium hydroxide solution to between pH 12 and 13. The same EDTA titrant was used as in the method for total hardnes s. Calcium, magnesium, and ammonium were measured on a Dionex ICS 3000 ion chromatograph (IC) using IonPac CG12A guard and CS12A analytical columns, cation self regenerating suppressor, 20 mM methanesulfonic acid eluent at 1.0 mL/min, and a 25 L sample l oop. Standard solutions were prepared using calcium chloride, magnesium chloride, and ammonium chloride. Phosphate was also measured on the Dionex ICS 300 ion chromatograph with an IonPac AG22 guard and AS22 analytical column, an anion self regenerating su ppressor, eluent composition of 4.5 mM Na 2 CO 3 /1.4 mM NaHCO 3 (AS22 eluent concentrate, Dionex), eluent flow rate of 1.2 mL/min, and a 25 L sample loop. The precision of these measurements was monitored by calculating the percent difference between duplicat e samples. The calibration check standards were monitored to ensure that they fell within 10% of the known values for accuracy.

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45 Experiment Main Question Studied Parameters b I Can CER remove magnesium and calcium from fresh urine? CER dose Ca / Mg concentration Composition of fresh urine II Will magnesium and calcium removal by CER affect the composition or amount of precipitates formed? Composition of fully hydrolyzed urine Ca/Mg/ PO 4 concentrations Precipitates formed III How does PO 4 concentration affect precipitation? Equilibrium models Ca/Mg/PO 4 concentrations Figure 4 1 Overview of lab experiments, main research questions and studied parameters Problem: Magnesium and calcium phosphate minerals inhibit waterless urinals effec tiveness Problem: Few studies examine precipitation in undiluted, completely hydrolyzed urine. Lack of agreement and validity of urine precipitation models. I II & III

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46 Figure 4 2 Process sche matic for precipitation experiments using synthetic aged urine Table 4 1 Chemical concentrations in fresh human urine and the final synthetic fresh urine mixture Constituent Average in Fresh Urine Final Synthetic Fresh Urine Urea (mmol N/L) 550 550 Ca 2+ (mmol/L) 4.7 4.3 Mg 2+ (mmol/L) 4.1 3.85 Na + (mmol/L) 113 136.9 Cl (mmol/L) 107 151 SO 4 2 (mmol/L) 15.6 16.1 NH 3 (mmol N/L) 34.2 37.5 K + (mmol/L) 56.3 56.3 PO 4 3 (mmol P/L) 23.9 0 pH 6.2 6.9 Ionic Strength 0.206 0.1997 Note: Average fresh urine data obtained from (Udert et al, 2003)

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47 Table 4 2 Chemical composition of calcium and magnesium free simulated hydrolyzed urine Constituent Synthetic Aged Urine Urea (mmol N/L) 0 Ca 2+ (mmol/L) 0 Mg 2+ (mmol/L) 0 Na + (mmol/L) 106.9 Cl (mmol/L) 170 SO 4 2 (mmol/L) 16 NH 3 (mmol N/L) 288 K + (mmol/L) 46 PO 4 3 (mmol P/L) 23.9 NH 4 + (mmol N/L) 339 HCO 3 2 (mmol/L) 266 pH a 9.069 Ionic Strength a 0.5665 a : Calculated by Visual MINTEQ Table 4 3 Chemic al composition of synthetic phosphate free simulated hydrolyzed urine solutions Constituent Phosphate free (both Ca and Mg) Calcium Only (phosphate free) Magnesium Only (phosphate free) Urea (mmol N/L) 0 0 0 Ca 2+ (mmol/L) 4.7 4.7 0 Mg 2+ (mmol/L) 4.1 0 4.1 Na + (mmol/L) 83 83 83 Cl (mmol/L) 453.6 445.4 178.2 SO 4 2 (mmol/L) 16 16 16 NH 3 (mmol N/L) 288 288 288 K + (mmol/L) 46 46 46 HCO 3 2 (mmol/L) 0 0 266 PO 4 3 (mmol P/L) 0 NH 4 + (mmol N/L) 339 339 339 pH a 9.260 9.2 9.1 Ionic Strength a 0.4752 0.4 662 0.5263 a : Calculated by Visual MINTEQ

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48 CHAPTER 5 RESULTS 5.1 Ion Exchange Experiments using Fresh Urine Magnesium and calcium concentrations in the synthetic fresh urine following the batch ion exchange experiments were measured by both ion chromatog raphy and hardness titration s The two concentrations as a function of C ER dose can be seen in Figures 5 1 and 5 2 The values between the two techniques are similar and the concentration can be seen to decrease as the CER dose increase d 5.2 Precipitatio n Experiments in Simulated Hydrolyzed Urine 5.2.1 Concentrations of calcium and magnesium added The amount of calcium and magnesium added to the synthetic aged urine was dependent on the results of the ion exchange experiments using fresh urine. The remova ls found for each CER dose were averaged to find the concentration of magnesium and calcium that reflected what would remain after cation exchange treatment. Due to the resins higher affinity for calcium, the range of calcium added was much wider than that of magnesium. One sample was meant to represent no cation exchange treatment and received a dose of 4.7 mmol/L calcium and 4.1 mmol/L magnesium. A blank sample without calcium or magnesium addition was also used. The entire range of added concentrations can be seen in Table 5 1 5.2.2 Precipitation of c alcium, magnesium, and phosphate The amount of calcium that remained in the aged urine after the removal of the precipitate ranged from 0.67 mmol/L, in the samples representing no cation exchange, to 0.39 mmol/L, in the samples dosed with 40 mL/L of CER. Levels of magnesium in the filtered samples did not follow a trend with resin dosage but remained around an

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49 average of 0.68 mmol/L. Phosphate showed a ranged in concentration from 16 mmol/L to 19 mmol/L. Me asurement error could be an issue d ue to the dilution required for phosphate analysis on the ion chromotograph. The remaining amount of phosphate followed a good overall trend, apart from sample A, which has a higher concentration than sample B, contrar y t o what was expected. Figure 5 3 shows the initial amount of each element added to each sample and the concentrations remaining in the filtered samples. 5.2.3 Mass of precipitate At every CER dose precipitation was obse rved almost immediately. Table 5 2 sh ows the dry mass of each precipitate collected for each resin dose. The decrease in mass is also plotted against CER dose and can be seen in Figure 5 4 5 .3 Phosphate Dosing Precipitation Experiments The two graphs below show the amount of HAP and struvite precipitated at e ach dose of phosphate. Figure 5 5 depicts HAP precipitation both with and without magnesium present. HAP, though it may not be the only calcium phosphate mineral present, is used as a benchmark because it has similar phosphate to calcium ratios to the other calcium phosphate minerals and it will be the only mineral present at equilibrium. Further discussion of this issue can be found in sections 4.7 and 4. 8. Figure 5 6 shows the struvite that precipitated with the added phosphorus, one d ata set shows the precipitation in the presence of calcium, the other in the calcium free urine. The precipitation of calcium in the presence of magnesium is lower than in the magnesium free urine at lower doses of phosphate. This difference could signal t hat when phosphate is the limiting factor in urine precipitation of struvite precedes HAP formation.

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50 F igure 5 1 Jar test results showing magnesium concentration as a function of resin dose for both detection methods (C 0 = 3.85 mmol/L). Figure 5 2 Ja r test results showing calcium concentration as a function of resin dose for both detection methods (C 0 = 4.3 mmol/L).

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51 Figure 5 3 Graphs showing amount of calcium, magnesium, and phosphate initially added to each sample (on left) and rema ining in each sample after precipitation (on right). Table 5 1 provides description of samples.

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52 Figure 5 4 Graph depicting the decreasing mass of precipitate collect ed as CER dose increases Figure 5 5 Amount of HAP formed in simulated hydroloyzed u rine at specific doses of phosphate with and without magnesium present. The vertical line represents the dose of phosphate that satisfies complete struvite precipitation with magnesium.

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53 Figure 5 6 Amount of struvite formed in fully hydrolyzed urine at varying phosphate doses with and without calcium present.

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54 Table 5 1 Amount of calcium and magnesium added to samples to represent treatment at various CER doses Sample A B C D E F CER dose (mL/L) 0 6 10 20 30 40 Calcium added ( mmol/L) 4.7 3.15 2.72 1.4 1.044 0.676 Magnesium added (mmol/L) 4.1 3.95 3.71 3.6 3.18 2.12 Table 5 2 Mass of dried precipitate collected after filtration of samples Sample Precipitate collected (g) A 0.1818 B 0.15705 C 0.13395 D 0.08885 E 0.0596 F 0.0034 5

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55 CHAPTER 6 DISCUSSION 6.1 Accuracy and Comparison of Ion Chromatography (IC) and Titration Measuring Techniques The IC data appears accurate for most values however, a few values deviated greatly from the overall trend ( Figures 5 1 and 5 2 ) This i s a result of the fact that the IC can have instrument error that can sometimes lead to results that are erroneously high or no t displayed at all. Figures 5 1 and 5 2 show that while there is slight variability among the IC and titration methods for measur ements of calcium and magnesium both are able to give relatively reliable values. All subsequent data are based on titration methods because of the error associated with the necessary dilutions for the IC 6.2 Calcium and Magnesium Cation Exchange Isother ms in Fresh Urine Treatment with cation exchange resin was able to achieve removal of both magnesium and calcium from the synthetic fresh urine. However, the removal of calcium was much greater than that of magn esium. The highest dosage of resin was able to remove about 90% of the calcium but only about 40% of the magnesium. An isotherm for the CER was determined by graphing the concentration of calcium and magnesium on the CER phase as a function of the concentration of calcium and magnesium remaining in solution ( Figure 6 1 ) The concentration on the CER was found by subtracting the concentration left in solution from the initial concentration divided by the mass of dry resin The isotherms further highlight the preference of the CER for calcium. As the calcium concentration in the solution increase, the amount on the CER surface also increases. For magnesium however, the concentration on the resin remains steady even as the magnesium in solution increases.

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56 Calculations of the exchange capacity at each C ER dose and the equivalent magnesium and calcium removed by the resin showed that the CER was between 17% and 33% saturated with magnesium and calcium ions. This low saturation is most likely due to the high competition from other ions like sodium and pota ssium. At a resin do s e of 6 mL/L there is about 13 more sodium and 5 more potassium in the urine than exchange sites available on the CER. The fact that the removal of magnesium and ivity for magnesium and calcium over other monovalent ions. 6.3 Struvite and HAP Saturation Index Calculations The next step was to see whether or not the removal by ion exchange would change the amount of HAP and struvite that would precipitate in the sy stem. A common calculation used to determine whether or not mineral precipitation will occur is the saturation index (SI) From Essington ( 2004) it is known that: SI = log(IAP/K sp ) (5 1) Where K sp is the solubility product and IAP is the ion activity product. If the SI is positive, the solution is supersaturated and the mineral with will precipitate, while if the SI is negative the solution is undersaturated and no precipitation will occur (Essington 2004) For HAP and struvite, the following equations govern SI calculations: 2+ + NH 4 + + PO 4 3 pK sp = 13.15 (5 2) IAP= Mg2+ [ Mg 2+ NH4+ [NH 4 + PO43 [PO 4 3 ] (5 3) 2+ + 3PO 4 3 + H + pK sp = 57.5 (5 4) IAP= Ca2+ [Ca 2+ ] 5 PO43 [PO 4 3 ] 3 H+ [H + ] (5 5)

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57 For accuracy, the SI values w ere determined using Visual MINTEQ, version 3.0 (Visual MINTEQ 2011) a computer modeling software that allows for specific calculations of activities, SI, and IAP by inputting the chemical composition of a solution. Since precipitation of urine is trigge red by urea hydrolysis (Udert 2003b) the constituents entered into Visual MINTEQ were that of the simulated hydrolyzed urine, the calcium and magnesium concentrations were then varied to represent the amount remaining after each CER dose. If any of the s concentrations resulted in a negative SI value for either HAP or struvite then it could be assumed that precipitation could be prevented by that CER dose. The calculated SI for HAP and struvite for each sample can be seen in Fi gure 6 2 F or both minerals, the SI are positive in all IX treated samples, indicating that precipitation could be possible. However, a positive SI only indicates that precipitation is thermodynamically favorable and does not give any indication of how muc h precipitation can be expected and at what rate For these reasons, the following experiments were meant to quantify the precipitation of minerals .The SI of both minerals in sample A, representing non IX treated urine are very similar to what Udert ( 2003 c) found in undiluted hydrolyzed urine. This agreement leads us to assume that the model can produce accurate SI values for HAP and struvite in urine and gives confidence in the calculated values of the other samples. 6.4 Precipitation Reduction in Cation Exchange Treated Urine The goal of this experiment was to measure and quantify the difference in the HAP and struvite formation at different resin doses. The SI calculations in the previous section showed that precipitation would occur at even the highest CER dose, but was unable to show the amount that would form The data of the remaining magnesium,

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58 calcium, and phosphate in the filtrate shown in Section 5.2.1 was compared to the added calcium and magn esium stock solutions as well as the concentration of phosphate in the aged urine solution. By subtracting the amount found in the filtrate from the initial concentrations, the fraction of magnesium, calcium, and phosphate that precipitated out during the mixing period was estimated. Below in Figure 6 3 the fraction of each element that was precipitated is shown for each resin dose. Figure 6 1 shows that the fraction of calcium precipitate is most affected by the change in CER dose. With no ion exchange treatment, about 86% of the calcium is precipitated and at the highest CER dose of 40 mL/L that percentage is reduced to 42%. The precipitation of magnesium is less affected by the change in resin dose and remains almost constant with 98% precipitated. The precipitation of phosphate, which is affected by both HAP and struvite formation, is dependent on the levels of both magnesium and calcium. The reduction in calcium precipitation, also leads to a reduction in phosphate precipitation from about 33% to 19%. 6.5 Mass of Struvite and HAP Precipitates The measur ed concentration of magnesium and calcium precipitated were used to determine the theoretical amount of struvite and HAP precipitated. Struvite was determined by the 1:1 stoichi o metric molar ratio between magnesium and s truvite. Moles of HAP formed was cal culated from the 1:5 ratio of HAP to calcium. These calculations are based on th e fact that in undiluted urine HAP and struvite are the main precipitates found (Udert 2003c) and that all of the calcium and magnesium precipitated can be assumed to be assim ilated entirely into HAP and struvite, respectively. Once the molar concentrations of struvite and HAP were found, they were adjusted by the sample size and molecular weights to estimate the theoretical mass of

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59 each solid formed in each sample. Figure 6 4 shows that the majority of the mass of precipitate can be contributed to struvite. In the sample that received no IX treatment the mass fraction of struvite is 0.71. These values are in agreement with Udert ( 2003c) who determined that in undiluted, aged ur ine struvite represents approximately 68% of the mass of precipitation, while HAP accounted for the additional 32%. With increasing CER dose, the mass fraction of struvite increases, with about 95% of the mass at the highest resin dose being struvite. Th e much higher mass fraction of struvite hinders the effectiveness of cation exchange to reduce the precipitation potential of urine. The struvite formation is a result of the remaining magnesium because the CER shows greater selectivity for calcium. The hi ghest CER dose effectively removed around 90% of the calcium and 40% of magnesium in the fresh urine T he calculations indicate the mass of precipitate would be about 38% of non ion exchange treated urine. Since the remaining mass of precipitate is almost purely struvite, higher magnesium removal would most likely greatly improve precipitation reduction. Finding an alternative cation exchange resin that has a higher affinity for magnesium could provide a way to lower the amount of struvite precipitated. Le vanmao et al. ( 1994) found that natural zeolite Na X provided 52.5% magnesium removal from solution at room temperature and 69.7% removal at 45 C. The average temperature of fresh urine is about 37 C which would allow for a substantially higher amount of m agnesium removal from urine than shown by the Amberlite 200c. Treatment with CER may not be able to drastically reduce the precipitation formed in hydrolyzed urine, however, it may provide a way to further another technology used in

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60 urine treatment. The id ea of controlled precipitation, collection, and use of as a fertilizer of struvite in source separated urine has been s uggested for nutrient recycling (Harada et al., 2006; Ronteltap et al., 2007; Wilsenach et al., 2007b ; Etter et al., 2011). However, most studies have determined that precipitation of pure struvite would require the addition of both magnesium and phosphate to fully utilize the nutrients in urine at a stoichiometric ratio (Larsen and G ujer, 1996; Kabdasli et al. 2006 ) Furthermore, Hao et a l. ( 2008) determined that the presence of calcium ions inhibits precipitation of pure struvite. Removal of calcium prior to urea hydrolysis would lower the phosphate lost to HAP precipitation and increase the phosphate concentration in the source separated urine allowing for a higher natural struvite precipitation and reduction of needed phosphate addition. 6.6 Comparison of Calculated and Measured Phosphate Values In the above calculations, the amounts of struvite and HAP precipitated were determined sole ly on measured magnesium and calcium concentrations; the phosphate precipitated was assumed to be equal to the stoichiometric phosphate to calcium and phosphate to magnesium ratios found in HAP and struvite, respectively. The amount of phosphate precipitat ed based on these ratios was compared to the measured amount of phosphate precipitated in the sample as can be seen below in Figure 6 5 The measured amount of phosphate precipitated is greater than that calculate d based on stoichiometric ratios for all sa mples except A, which as previously mentioned, probably contained some experimental error. This difference could indicate the presence of additional phosphate minerals, or t he formation of other magnesium or calcium phosphate precipitates besides HAP and struvite. Both amorphous calcium phosphate (ACP) and octacalcium phosphate ( OCP ) are known precursors to HAP in

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61 urine precipitation, both are calcium phosphate minerals that incorporate a higher amount of phosphate. Their presence could cause the equilibr ium amount of phosphate precipitated to be less than measured. 6.7 Measured Mass vs. Theoretical Mass The theoretical mass of HAP and struvite discussed in the previous section can be the hydrated molecular weight of struvite. The actual measured mass of the collected solids can be Methods 2540 D. The same calculations used in section 4.5 to determine the am ount of precipitates based on the stoich io metric ratios to the measured calcium and magnesium mass. Figure 6 6 shows this calculated dry mass as well as the mass of th e collected solids. There is good agreement between to two data sets in the low CER dosage samples, but at the higher resin doses, the mass of collected solids is lower than what would be expected from the amount of calcium and magnesium that precipitated out of solution. The reason for the difference in masses at higher resin doses is not known. Calculations made to determine the mass fractions of struvite and HAP found in the dry solids can be compared to the collected precipitate m ass, as shown below in Figure 6 7 This graph is a version of Figure 6 4 in Section 6.5 but uses the dehydrated masses of struvite and HAP. The figure highlights the drastic reduction in struvite weight and the accuracy of the mass of solids collected at lower CER doses.

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62 6.8 Com parison of Measured and Calculated Precipitation Results to Modeled Results Visual MINTEQ was used to compare the experimental results to the modeled equilibrium results. Figures 6 8 6 10 shows the modeled amount of magnesium, calcium, and phosphate pre cipitated compared to the amount measured in the experiment. The results and model agree very well for magnesium, nearly 100% being precipitated at every resin dose. This tells us that precipitation of struvite in urine reaches equilibrium very quickly, wi th the 15 minute mixing time and that further storage will not change magnesium concentrations. The results for calcium, however, do not agree as well. The results showed, promisingly, that at the highest CER dose that only 40% of the calcium will be inco rporated into solids. However, the model shows that at equilibrium a majority of the calcium will precipitate. The amount precipitated will be different at each CER dose, due to the high removal of calcium, but as the model suggests that at equilibrium the amount incorporated into solids remains unchanged by CER treatment. This disagreement suggests that HAP formation did not reach equilibrium within the mixing time, which was based on research of struvite precipitation only (Ronteltap et al. 2007) Furthe r experiments should be conducted with a longer mixing time to see if calcium precipitation is reduced at all or if the Visual MINTEQ predications are accurate. Udert (2003b) showed that after 4.5 h of urea hydrolysis only 70% of calcium was precipitated b ut was precipitated as OCP. Due to the incomplete urea hydrolysis, the pH was about 8.9. House ( 1999) determined that in solutions with a pH above 9 (as in fully hydrolyzed urine) OCP is not a precursor to HAP but instead ACP is converted directly into HAP This suggests that ACP is most likely present i n the experimental precipitates Liu et al.

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63 ( 2001) found that at 25 C ACP is converted into HAP after 24 h. This suggests that as the urea is being hydrolyzed (and pH is below 9) OCP appears as the first cal cium phosphate mineral, as urea hydrolysis is complete (and pH is increased above 9) ACP appears and both are transformed slowly into HAP. The model predicted that phosphate precipitated at equilibrium would be less than measured during the experiments. T his most likely can be attributed to measurement error and does not indicate any change in precipitat e composition. However, analysis of the solids could provide insight to whether or not any additional phosphate solids were formed. Figures 6 11 and 6 12 show the amounts of struvite and HAP formed at each resin dose calculated from the measured calcium and magnesium concentrations and the Visual MINTEQ model. The results of HAP precipitated vary between the model and the calculate values. However, these fi gures highlight the decrease in both minerals, particularly HAP with CER treatment.

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64 Figure 6 1 I sotherm for magnesium and calcium removal as measured by titrations Figure 6 2 Calculated s aturation i ndex v alues for HAP and struvite in hydrolyzed u rine for various CER dosages Table 5 1 gives a description of the samples.

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65 Figure 6 3 Fractions of phosphate, magnesium and calcium precipitated in each sample after cation exchange treatment and mixing Figure 6 4 Mass fraction of solids expected to form in hydrolyzed urine based on magnesium and calcium measurements

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66 Figure 6 5 Phosphate precipitated in fully hydrolyzed urine as measured by ion chromatography and determined from stoichiometric ratios with measured magnesium and calcium F igure 6 6 Collected and calculated mass of dry precipitates for each CER dose

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67 Figure 6 7 mass at each CER dose Figure 6 8 Measured and modeled percent of magnesium precipita ted in ion exchange treated, simulated hydrolyzed urine

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68 F igure 6 9 Measured and modeled percent of calcium precipitated in ion exchange treated, simulated hydrolyzed urine Figure 6 10 Measured and modeled percent of phosphate precipitated in ion e xchange treated, simulated hydrolyzed urine

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69 Figure 6 11 Measured and modeled concentrations of struvite precipitated in ion exchange treated, simulated hydrolyzed urine Figure 6 12 Measured and modeled concentrations of HAP precipitated in ion ex change treated, simulated hydrolyzed urine

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70 CHAPTER 7 CONCLUSIONS AND FUTU RE WORK Though urine separation can provide many benefits to the environment, its widespread use and success is limited by the usability and operational issues of separation units. Many researches are attempting to quantify the main problems and provide solutions that will promote user acceptance. Economic feasibility, integration into the existing infrastructure, and urine taboos currently hinder this goal. Treatment options for sou rce separated urine are numerous. Nutrient recovery is one of the most desirable goals for urine treatment and one technology in particular struvite precipitation, has been studied extensively. Although r esearchers have attempted to optimize the precipita tion process in the laboratory, improvement in design of full scale units is needed before widespread use is possible. Experiments showed that CER was able to remove both magnesium and calcium from fresh urine. Calcium was preferentially removed, with abou t 90% removal at the highest resin dose M agnesium removal was less effect ive with only 50% removal at the highest resin dose. Subsequent experiments using simulated hydrolyzed urine showed that ion exchange treatment of urine could provide a reduction of the two most problematic minerals : HAP and struvite. Calculated results indicated a 70% reduction in the mass of precipitates formed at the highest resin dose. An equilibrium model determined that at all CER doses all magnesium and calcium would be precipi tated but, due to the removal seen by CER, mass of precipitates formed would decrease. Though ion exchange treatment may not be able to prevent problematic precipitation in urine separating systems, it may be useful as a pretreatment to nutrient recovery i n urine, specifically struvite precipitation. CER reduces the phosphate bound

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71 in precipitates lost in pipes, traps, and storage units, allowing for higher recovery rates in precipitation units. It also creates a favorable magnesium to calcium ratio for str uvite formation, enabling a more valuable product. Further research into the removal of magnesium and calcium from urine by other cation exchange resins could potentially show an even further reduction of mineral precipitates, especially if there is prefe rential removal of magnesium. Research on the impact of ion exchange treatment of urine as a pretreatment to struvite precipitation is needed to determine if calcium removal has a significant effect on the recoverable struvite. If calcium removal is determ ined to be useful, a resin with an even high er calcium preference should be studied. Alternatively, anion exchange resins could be used as a way of collecting and recovering phosphate before spontaneous precipitation occurs. This could eliminate not only the problematic clogging of units but also benefit nutrient recovery.

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72 LIST OF REFERENCES Abbona, F., Madsen H. E. L., Boistelle, R., 1986. The Initial Phases of Calcium and Magnesium Phosphates Precipitated from Solutions of High to Medium Concentratio ns. J. Cryst. Growth 74 (3), 581 590. Antoni ni, S., Paris, S., Clemens, J., 2008. Nitrogen and Phosphorus Recovery from Human Urine. In: SANSED Workshop Can Tho, 08. Barthlott, W. an d Neinhuis, C.,1997. Purity of the sacred lotus, or escape from contamin ation in biological surfaces. Planta 202 (1), 1 8. Basakcilardan Kabakci, S. Ipekoglu, A. N., Talinli, I., 2007. Precipitation of urinary phosphate. Environ. Eng. Sci. 24 (10), 1399 1408. Berndtsson, J. C., 2006. Experiences from the implementation of a urine separation system: Goals, planning, reality. Build. Environ. 41 (4), 427 437. Bridger, G. L., Sta rostka, R. W., Salutsky, M. L., 1962. Micronutrient Sources Metal Ammonium Phosphates as Fertilizers. J. Agric. Food Chem. 10 (3), 181 &. Brown, C. M., Ac kermann, D. K., Purich, D. L., 1994. Equil93 a Tool for Experimental and Clinical Urolithiasis. Urol. Res. 22 (2), 119 126. Buchanan, J. R. Mote, C. R., Robinson, R. B., 1994. Thermodynamics of Struvite Formation. Trans. ASAE 37 (2), 617 621. Cl esceri, E.R., Eaton, A.D., Greenberg, A.E., Rice, E.W., 2005. Standard Methods for the Examination of Water and Wastewater, 21 st Edition. Washington, DC: American Public Health Association, American Water Works Association and Water Environment Federation. Cordell, D., Drangert, J. O., White, S., 2009. The story of phosphorus: Global food security and food for thought. Global Environ. Change 19 (2), 292 305. Darn, S. M., Sodi, R., Ranganath, L. R., R oberts, N. B., Duffield, J. R., 2006. Experimental and c omputer modelling speciation studies of the effect of pH and phosphate on the precipitation of calcium and magnesium salts in urine. Clinical Chemistry and Laboratory Medicine 44 (2), 185 191. El Diwani, G., El Rafie, S., El Ibiari, N. N., El Aila, H. I., 2007. Recovery of ammonia nitrogen from industrial wastewater treatment as Struvite slow releasing fertilizer. Desalination 214 (1 3), 200 214. Essington, M. E., 2004. Soil and water chemistry : An integrative approach. CRC Press, Boca Raton.

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73 Etter, B., T illey E., Khadka, R., Udert, K. M., 2011. Low cost struvite production using source separated urine in Nepal. Water Res. 45 (2), 852 862. Hanaeus, J. Hellstrom, D., Johansson, E., 1997. A study of a urine separation in an ecological village in northern Sweden. Water Science and Technology 35 (9), 153 160. Hao, X., Wang, C. Lan L., van Loosdrecht, M. C. M., 2008. Struvite formation, analytical methods and effects of pH and Ca(2+). Water Science and Technology 58 (8), 1687 1692. Harada, H., Shimizu, Y. Miyagoshi, Y., Matsui, S., Matsuda, T., Nagasaka, T., 2006. Predicting struvite formation for phosphorus recovery from human urine using an equilibrium model. Water Science and Technology 54 ( 8), 247 255. Hellstrom, D., Johannson, E., Grennberg, K. (199 9) Storage of human urine: acidification as a method to inhibit decomposition of urea. Ecol. Eng. 12 (3 4), 253 269. House, W. A., 1999 The physico chemical conditions for the precipitation of phosphate with calcium. Environ. Technol. 20 (7), 727 733. Jo hnston, A. E. and Richards, I. R., 2003. Effectiveness of different precipitated phosphates as phosphorus sources for plants. Soil Use Manage. 19 (1), 45 49. Jonsson, H., 2002. Urine separation Swedish experiences. In: Urban areas rural areas and recy cling, NJF seminar 327, DARCOF Report. Tjele Denmark, 117 124 Jonsson, H., Stenstrom, T. A., Svens son, J., Sundin, A., 1997. Source separated urine nutrient and heavy metal content, water saving and faecal contamination. Water Science and Technology 35 ( 9), 145 152. Kabdasli, I., Tunay, O., Islek, C., Erdinc, E., Huskalar, S., Tatli, M. B., 2006a. Nitrogen recovery by urea hydrolysis and struvite precipitation from anthropogenic urine. Water Science and Technology 53 (12), 305 312. Karak, T. and Bhattacharyya, P., 2011. Human urine as a source of alternative natural fertilizer in agriculture: A flight of fancy or an achievable reality. Resour. Conserv. Recycling Kemacheevakul, P ., Polprasert, C., Shimizu, Y., 2011. Phosphorus recovery from human urine and anaerobically treated wastewater through pH adjustment and chemical precipitation. Environ. Technol. 32 (7), 693 698. Larsen, T. A., Maurer, M., Eggen, R. I. L., Pronk, W., Lienert, J., 2010. Decision support in u rban water management based on generic scenarios: The example of NoMix technology. J. Environ. Manage.

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74 Larsen, T. A. and Gujer, W., 2001 Waste design and source control lead to flexibility in wastewater management. Water Science and Technology 43 (5), 30 9 317. Larsen, T. A., Peters, I., Alder, A., Egg en, R., Maurer, M., Muncke, J., 2001. Re engineering the toilet for sustainable wastewater management. Environ. Sci. Technol. 35 (9), 192A 197A. Larsen, T. A. and Gujer, W., 1997 The concept of sustainable urban water management. Water Science and Technology 35 (9), 3 10. Larsen, T. A. and Gujer, W., 1996 Separate management of anthropogenic nutrient solutions (human urine). Water Science and Technology 34 (3 4), 87 94. Larsen, T. A., Alder, A. C., Eggen, R. I. L., Maurer, M., Lienert, J., 2009 Source Separation: Will We See a Paradigm Shift in Wastewater Handling? Environ. Sci. Technol. 43 (16), 6121 6125. Le Corre, K. S., Valsami Jones, E., Hobbs, P., Parsons, S. A., 2009. Phosphorus Recovery from Waste water by Struvite Crystallization: A Review. Crit. Rev. Environ. Sci. Technol. 39 (6), 433 477. Levanmao, R., Vu, N. T., Xiao, S. Y., Ramsaran, A., 1994. Modified Zeolites for the Removal of Calcium and Magnesium from Hard Water. Journal of Materials Chem istry 4 (7), 1143 1147. Li, X., R einhoudt, D., Crego Calama, M., 2007. What do we need for a superhydrophobic surface? A review on the recent progress in the preparation of superhydrophobic surfaces. Chem. Soc. Rev. 36 (8), 1350 1368. Lienert, J. and Lar sen, T. A., 2010 High Acceptance of Urine Source Separation in Seven European Countries: A Review. Environ. Sci. Technol. 44 (2), 556 566. L ind, B. B., Ban, Z., Byden, S., 2000. Nutrient recovery from human urine by struvite crystallization with ammonia adsorption on zeolite and wollastonite. Bioresour. Technol. 73 (2), 169 174. Liu, C. S., H uang, Y., Shen, W., Cui, J. H., 2001. Kinetics of hydroxyapatite precipitation at pH 10 to 11. Biomaterials 22 (4), 301 306. Liu, Z. G., Zhao, Q. L., Wang, K. Qiu, W., Li, W., Wang, J. F., 200 8. Comparison between complete and partial recovery of N and P from stale human urine with MAP crystallization. Journal of Environmental Engineering and Science 7 (3), 223 228. Maurer M., Pronk, W., Larsen, T. A., 2006 Treatment processes for source separated urine. Water Res. 40 (17), 3151 3166.

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77 BIOGRAPHICAL SKETCH Kyle Taylor graduated from the University of Florida, Gainesville FL in De cember 2010 with a BS in Envir onmental Engineering. In January 2011 she began stud ying to earn a ee in environmental e ngineering at the University of Florida