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Arve PH, Mason M, Randall DG, Simha P, Popat SC. Concomitant urea stabilization and phosphorus recovery from source-separated fresh urine in magnesium anode-based peroxide-producing electrochemical cells. WATER RESEARCH 2024; 256:121638. [PMID: 38691899 DOI: 10.1016/j.watres.2024.121638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 03/28/2024] [Accepted: 04/16/2024] [Indexed: 05/03/2024]
Abstract
In this study, we investigated the recovery of nitrogen (N) and phosphorus (P) from fresh source-separated urine with a novel electrochemical cell equipped with a magnesium (Mg) anode and carbon-based gas-diffusion cathode. Recovery of P, which exists primarily as phosphate (PO43-) in urine, was achieved through pH-driven precipitation. Maximizing N recovery requires simultaneous approaches to address urea and ammonia (NH3). NH3 recovery was possible through precipitation in struvite with soluble Mg supplied by the anode. Urea was stabilized with electrochemically synthesized hydrogen peroxide (H2O2) from the cathode. H2O2 concentrations and resulting urine pH were directly proportional to the applied current density. Concomitant NH3 and PO43- precipitation as struvite and urea stabilization via H2O2 electrosynthesis was possible at lower current densities, resulting in urine pH under 9.2. Higher current densities resulted in urine pH over 9.2, yielding higher H2O2 concentrations and more consistent stabilization of urea at the expense of NH3 recovery as struvite; PO43- precipitation still occurred but in the form of calcium phosphate and magnesium phosphate solids.
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Affiliation(s)
- Philip H Arve
- Department of Environmental Engineering and Earth Sciences, Clemson University, Clemson, SC, USA
| | - Marc Mason
- Department of Environmental Engineering and Earth Sciences, Clemson University, Clemson, SC, USA
| | - Dyllon G Randall
- Department of Civil Engineering, University of Cape Town, Cape Town, South Africa
| | - Prithvi Simha
- Department of Energy and Technology, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Sudeep C Popat
- Department of Environmental Engineering and Earth Sciences, Clemson University, Clemson, SC, USA.
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2
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Al-Juboori RA, Al-Shaeli M, Aani SA, Johnson D, Hilal N. Membrane Technologies for Nitrogen Recovery from Waste Streams: Scientometrics and Technical Analysis. MEMBRANES 2022; 13:15. [PMID: 36676822 PMCID: PMC9864344 DOI: 10.3390/membranes13010015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/03/2022] [Revised: 12/19/2022] [Accepted: 12/20/2022] [Indexed: 06/17/2023]
Abstract
The concerns regarding the reactive nitrogen levels exceeding the planetary limits are well documented in the literature. A large portion of anthropogenic nitrogen ends in wastewater. Nitrogen removal in typical wastewater treatment processes consumes a considerable amount of energy. Nitrogen recovery can help in saving energy and meeting the regulatory discharge limits. This has motivated researchers and industry professionals alike to devise effective nitrogen recovery systems. Membrane technologies form a fundamental part of these systems. This work presents a thorough overview of the subject using scientometric analysis and presents an evaluation of membrane technologies guided by literature findings. The focus of nitrogen recovery research has shifted over time from nutrient concentration to the production of marketable products using improved membrane materials and designs. A practical approach for selecting hybrid systems based on the recovery goals has been proposed. A comparison between membrane technologies in terms of energy requirements, recovery efficiency, and process scale showed that gas permeable membrane (GPM) and its combination with other technologies are the most promising recovery techniques and they merit further industry attention and investment. Recommendations for potential future search trends based on industry and end users' needs have also been proposed.
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Affiliation(s)
- Raed A. Al-Juboori
- NYUAD Water Research Centre, New York University, Abu Dhabi Campus, Abu Dhabi P.O. Box 129188, United Arab Emirates
| | - Muayad Al-Shaeli
- Department of Engineering, University of Luxembourg, 2, Avenue de l’Université, L-4365 Esch-sur-Alzette, Luxembourg
| | - Saif Al Aani
- The State Company of Energy Production-Middle Region, Ministry of Electricity, Baghdad 10013, Iraq
| | - Daniel Johnson
- NYUAD Water Research Centre, New York University, Abu Dhabi Campus, Abu Dhabi P.O. Box 129188, United Arab Emirates
| | - Nidal Hilal
- NYUAD Water Research Centre, New York University, Abu Dhabi Campus, Abu Dhabi P.O. Box 129188, United Arab Emirates
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3
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Martínez-Castrejón M, López-Díaz JA, Solorza-Feria O, Talavera-Mendoza O, Rodríguez-Herrera AL, Alcaraz-Morales O, Hernández-Flores G. Environmental, Economic, and Social Aspects of Human Urine Valorization through Microbial Fuel Cells from the Circular Economy Perspective. MICROMACHINES 2022; 13:2239. [PMID: 36557539 PMCID: PMC9785870 DOI: 10.3390/mi13122239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 12/08/2022] [Accepted: 12/09/2022] [Indexed: 06/17/2023]
Abstract
Population growth increases the challenge of meeting basic human needs, such as water, a limited resource. Consumption habits and water pollution have compromised natural resources to unsustainable levels. Sustainable effluent treatment practices, such as decentralized systems focused on energy, nutrients, and water recovery, have attracted the attention of the scientific community. Human urine (HU) is a physiological liquid waste whose main component is water (~95%). HU has a significant amount of nutrients, such as N, P, K, and organic matter, which are usually lacking in fecal coliforms. Therefore, the possibility exists of recovering nutrients and energy from HU using sustainable and non-sustainable technologies. Treating HU in bioelectrochemical systems (BES) is a novel alternative to obtaining byproducts from this effluent more sustainably than in electrochemical systems. Microbial fuel cells (MFCs) are an interesting example, contributing to HU revalorization from unwanted waste into a valuable resource of nutrients, energy, and water. Even when urine-operated MFCs have not generated attractive potential outputs or produced considerable amounts of bioelectricity, this review emphasizes HU advantages as nutrients or water sources. The aim of this review was to analyze the current development of BES for HU treatment based on the water circular economy, discussing challenges and perspectives researchers might encounter.
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Affiliation(s)
- Mariana Martínez-Castrejón
- Centro de Ciencias de Desarrollo Regional, Universidad Autónoma de Guerrero, Privada de Laurel No. 13, Col. El Roble, Acapulco C.P. 39640, Guerrero, Mexico
| | - Jazmin A. López-Díaz
- Escuela Superior de Ciencias de la Tierra, Universidad Autónoma de Guerrero, Ex hacienda San Juan Bautista s/n, Taxco el Viejo C.P. 40323, Guerrero, Mexico
| | - Omar Solorza-Feria
- Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Department of Chemistry, Av. Instituto Politécnico Nacional 2508, Col. San Pedro Zacatenco, Delegación C.P. 07360, Gustavo A. Madero, Mexico
| | - Oscar Talavera-Mendoza
- Escuela Superior de Ciencias de la Tierra, Universidad Autónoma de Guerrero, Ex hacienda San Juan Bautista s/n, Taxco el Viejo C.P. 40323, Guerrero, Mexico
| | - América L. Rodríguez-Herrera
- Centro de Ciencias de Desarrollo Regional, Universidad Autónoma de Guerrero, Privada de Laurel No. 13, Col. El Roble, Acapulco C.P. 39640, Guerrero, Mexico
| | - Osbelia Alcaraz-Morales
- Facultad de Arquitectura y Urbanismo, Universidad Autónoma de Guerrero, Av. Juárez No. 38 Interior. C.U. Zona Norte, Chilpancingo C.P. 39000, Guerrero, Mexico
| | - Giovanni Hernández-Flores
- CONACYT-Escuela Superior de Ciencias de la Tierra, Universidad Autónoma de Guerrero, Ex Hacienda San Juan Bautista s/n, Taxco el Viejo C.P. 40323, Guerrero, Mexico
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4
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McCartney SN, Fan H, Watanabe NS, Huang Y, Yip NY. Donnan dialysis for phosphate recovery from diverted urine. WATER RESEARCH 2022; 226:119302. [PMID: 36369681 DOI: 10.1016/j.watres.2022.119302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Revised: 10/17/2022] [Accepted: 10/25/2022] [Indexed: 06/16/2023]
Abstract
There is a critical need to shift from existing linear phosphorous management practices to a more sustainable circular P economy. Closing the nutrient loop can reduce our reliance on phosphate mining, which has well-documented environmental impacts, while simultaneously alleviating P pollution of aquatic environments from wastewater discharges that are not completely treated. The high orthophosphate, HxPO4(3-x)-, content in source-separated urine offers propitious opportunities for P recovery. This study examines the use of Donnan dialysis (DD), an ion-exchange membrane-based process, for the recovery of orthophosphates from fresh and hydrolyzed urine matrixes. H2PO4- transport against an orthophosphate concentration gradient was demonstrated and orthophosphate recovery yields up to 93% were achieved. By adopting higher feed to receiver volume ratios, DD enriched orthophosphate in the product stream as high as ≈2.5 × the initial urine feed concentration. However, flux, selectivity, and yield of orthophosphate recovery were detrimentally impacted by the presence of SO42- and Cl- in fresh urine, and the large amount of HCO3- rendered hydrolyzed urine practically unsuitable for P recovery using DD. The detrimental effects of sulfate ions can be mitigated by utilizing a monovalent ion permselective membrane, improving selectivity for H2PO4- transport over SO42- by 3.1 × relative to DD with a conventional membrane; but the enhancement was at the expense of reduced orthophosphate flux. Critically, widely available and low-cost/waste resources with sufficiently high Cl- content, such as seawater and waste water softening regenerant rinse, can be employed to improve the economic viability of orthophosphate recovery. This study shows the promising potential of DD for P recovery and enrichment from source-separated urine.
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Affiliation(s)
- Stephanie N McCartney
- Department of Earth and Environmental Engineering, Columbia University, New York, New York 10027-6623, United States
| | - Hanqing Fan
- Department of Earth and Environmental Engineering, Columbia University, New York, New York 10027-6623, United States
| | - Nobuyo S Watanabe
- Department of Chemistry, Barnard College, New York, New York 10027-6598, United States
| | - Yuxuan Huang
- Department of Earth and Environmental Engineering, Columbia University, New York, New York 10027-6623, United States
| | - Ngai Yin Yip
- Department of Earth and Environmental Engineering, Columbia University, New York, New York 10027-6623, United States; Columbia Water Center, Columbia University, New York, New York 10027-6623, United States.
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5
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Yu C, Yin W, Yu Z, Chen J, Huang R, Zhou X. Membrane technologies in toilet urine treatment for toilet urine resource utilization: a review. RSC Adv 2021; 11:35525-35535. [PMID: 35493188 PMCID: PMC9043190 DOI: 10.1039/d1ra05816a] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Accepted: 10/12/2021] [Indexed: 11/21/2022] Open
Abstract
Membrane technologies have broad potential in methods for separating, collecting, storing, and utilizing urine collected from toilets. Recovering urine from toilets for resource utilization instead of treating it in a sewage treatment plant not only reduces extra energy consumption for the degradation of N and P but also saves energy in chemical fertilizer production, which will contribute to carbon emission reduction of 12.19-17.82 kg kgN -1 in terms of N alone. Due to its high efficiency in terms of volume reduction, water recycling, nutrient recovery, and pollutant removal, membrane technology is a promising technology for resource utilization from urine collected from toilets. In this review, we divide membrane technologies for resource utilization from urine collected from toilets into four categories based on the driving force: external pressure-driven membrane technology, vapor pressure-driven membrane technology, chemical potential-driven membrane technology, and electric field-driven membrane technology. These technologies influence factors such as: recovery targets and mechanisms, reaction condition optimization, and process efficiency, and these are all discussed in this review. Finally, a toilet with source-separation is suggested. In the future, membrane technology research should focus on the practical application of source-separation toilets, membrane fouling prevention, and energy consumption evaluation. This review may provide theoretical support for the resource utilization of urine collected from toilets that is based on membrane technology.
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Affiliation(s)
- Chengzhi Yu
- State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University Shanghai 200092 China +86-21-6598-2693
| | - Wenjun Yin
- State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University Shanghai 200092 China +86-21-6598-2693
| | - Zhenjiang Yu
- State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University Shanghai 200092 China +86-21-6598-2693
| | - Jiabin Chen
- State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University Shanghai 200092 China +86-21-6598-2693
| | - Rui Huang
- The Third Clinical Medical College, Zhejiang Chinese Medical University Hangzhou 310053 China
| | - Xuefei Zhou
- State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University Shanghai 200092 China +86-21-6598-2693
- Shanghai Institute of Pollution Control and Ecological Security, Tongji University Shanghai 200092 China
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6
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De Paepe J, De Pryck L, Verliefde ARD, Rabaey K, Clauwaert P. Electrochemically Induced Precipitation Enables Fresh Urine Stabilization and Facilitates Source Separation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:3618-3627. [PMID: 32049503 DOI: 10.1021/acs.est.9b06804] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Source separation of urine can enable nutrient recycling, facilitate wastewater management, and conserve water. Without stabilization of the urine, urea is quickly hydrolyzed into ammonia and (bi)carbonate, causing nutrient loss, clogging of collection systems, ammonia volatilization, and odor nuisance. In this study, electrochemically induced precipitation and stabilization of fresh urine was successfully demonstrated. By recirculating the urine over the cathodic compartment of an electrochemical cell, the pH was increased due to the production of hydroxyl ions at the cathode. The pH increased to 11-12, decreasing calcium and magnesium concentrations by >80%, and minimizing scaling and clogging during downstream processing. At pH 11, urine could be stabilized for one week, while an increase to pH 12 allowed urine storage without urea hydrolysis for >18 months. By a smart selection of membranes [anion exchange membrane (AEM) with a cation exchange membrane (CEM) or a bipolar membrane (BPM)], no chemical input was required in the electrochemical cell and an acidic stream was produced that can be used to periodically rinse the electrochemical cell and toilet. On-site electrochemical treatment, close to the toilet, is a promising new concept to minimize clogging in collection systems by forcing controlled precipitation and to inhibit urea hydrolysis during storage until further treatment in more centralized nutrient recovery plants.
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Affiliation(s)
- Jolien De Paepe
- Center for Microbial Ecology and Technology (CMET), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Gent, Belgium
- Department d'Enginyeria Química, Biològica i Ambiental, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, Spain
- Center for Advanced Process Technology and Urban Resource Efficiency (CAPTURE), Ghent University, Coupure Links 653, 9000 Gent, Belgium
| | - Laurens De Pryck
- Center for Microbial Ecology and Technology (CMET), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Gent, Belgium
| | - Arne R D Verliefde
- Center for Advanced Process Technology and Urban Resource Efficiency (CAPTURE), Ghent University, Coupure Links 653, 9000 Gent, Belgium
- Particle and Interfacial Technology Group (PaInt), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Gent, Belgium
| | - Korneel Rabaey
- Center for Microbial Ecology and Technology (CMET), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Gent, Belgium
- Center for Advanced Process Technology and Urban Resource Efficiency (CAPTURE), Ghent University, Coupure Links 653, 9000 Gent, Belgium
| | - Peter Clauwaert
- Center for Microbial Ecology and Technology (CMET), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Gent, Belgium
- Center for Advanced Process Technology and Urban Resource Efficiency (CAPTURE), Ghent University, Coupure Links 653, 9000 Gent, Belgium
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7
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Singla J, Sangal VK, Singh A, Verma A. Application of mixed metal oxide anode for the electro-oxidation/disinfection of synthetic urine: Potential of harnessing molecular hydrogen generation. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2020; 255:109847. [PMID: 31783214 DOI: 10.1016/j.jenvman.2019.109847] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Revised: 10/07/2019] [Accepted: 11/07/2019] [Indexed: 05/03/2023]
Abstract
The efficacy of electro-oxidation has been checked for the deterioration of synthetic urine (SU) using mixed metal oxide anode along with the potential of harnessing the commercially useful byproduct i.e. molecular hydrogen gas. The results from batch have been used to execute the scale-up studies for the continuous electro-oxidation treatment of SU in a photovoltaic driven reactor. The effect of different operational variables like pH, time, current density and N/Cl ratio on process efficiency was evaluated in terms of %COD removal and specific energy consumption using response surface methodology. The results showed that 87.25% removal in COD and 85.88% in TOC were achieved in 8.8 h. The complete deactivation of E. coli spiked synthetic urine wastewater was achieved in 45 min only. The main strength lies in the demonstration of the significant reduction in treatment time to 6 h by incorporating dual effect i.e. Photo-electrocatalysis. The anode used was proven to be stable and effective even after 100 recycles (207.5 h). The intermediates formed during the treatment process were analyzed through LC-MS. The techno-economic analysis for the proposed technology under optimized conditions was calculated to be 0.85 $/kg of COD removed.
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Affiliation(s)
- Jayishnu Singla
- School of Energy and Environment, Thapar Institute of Engineering and Technology, Patiala, Punjab, India
| | - Vikas K Sangal
- Department of Chemical Engineering, Malaviya National Institute of Technology, Jaipur, Rajasthan, India.
| | - Amanjit Singh
- Research and Development, Consumer Product Division, HSIL Limited, Gurgaon, Haryana, India
| | - Anoop Verma
- School of Energy and Environment, Thapar Institute of Engineering and Technology, Patiala, Punjab, India.
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8
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Silva JF, Graça NS, Ribeiro AM, Rodrigues AE. Electrocoagulation process for the removal of co-existent fluoride, arsenic and iron from contaminated drinking water. Sep Purif Technol 2018. [DOI: 10.1016/j.seppur.2017.12.055] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
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9
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Parametric optimization for the treatment of human urine metabolite, creatinine using electro-oxidation. J Electroanal Chem (Lausanne) 2018. [DOI: 10.1016/j.jelechem.2017.12.061] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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10
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Wu S, Zou S, Liang G, Qian G, He Z. Enhancing recovery of magnesium as struvite from landfill leachate by pretreatment of calcium with simultaneous reduction of liquid volume via forward osmosis. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 610-611:137-146. [PMID: 28803191 DOI: 10.1016/j.scitotenv.2017.08.038] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2017] [Revised: 08/03/2017] [Accepted: 08/04/2017] [Indexed: 06/07/2023]
Abstract
Landfill leachate contains substances that can be potentially recovered as valuable resources. In this study, magnesium in a landfill leachate was recovered as struvite with calcium pretreatment; meanwhile, the leachate volume was reduced by using a submerged forward osmosis (FO) process, thereby enabling significant reduction of further treatment footprint and cost. Without pretreatment, calcium exhibited strong competition for phosphate with magnesium. The pretreatment with a Ca2+: CO32- molar ratio of 1:1.4 achieved a relatively low loss rate of Mg2+ (24.1±2.0%) and high Ca2+ removal efficiency (89.5±1.7%). During struvite recovery, 98.6±0.1% of magnesium could be recovered with a significantly lower residual PO43--P concentration (<25mgL-1) under the condition of (Mg+Caresidual): P molar ratio of 1:1.5 and pH9.5. The obtained struvite had a similar crystal structure and composition (19.3% Mg and 29.8% P) to that of standard struvite. The FO process successfully recovered water from the leachate and reduced its volume by 37%. The configuration of calcium pretreatment - FO - struvite recovery was found to be the optimal arrangement in terms of FO performance. These results have demonstrated the feasibility of magnesium recovery from landfill leachate and the importance of the calcium pretreatment, and will encourage further efforts to assess the value and purity of struvite for commercial use and to develop new methods for resource recovery from leachate.
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Affiliation(s)
- Simiao Wu
- School of Environmental and Chemical Engineering, Shanghai University, No. 99, Shangda Road, Shanghai 200444, PR China; Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
| | - Shiqiang Zou
- Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
| | - Guannan Liang
- School of Environmental and Chemical Engineering, Shanghai University, No. 99, Shangda Road, Shanghai 200444, PR China
| | - Guangren Qian
- School of Environmental and Chemical Engineering, Shanghai University, No. 99, Shangda Road, Shanghai 200444, PR China
| | - Zhen He
- Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
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11
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Randall DG, Krähenbühl M, Köpping I, Larsen TA, Udert KM. A novel approach for stabilizing fresh urine by calcium hydroxide addition. WATER RESEARCH 2016; 95:361-9. [PMID: 27055084 PMCID: PMC4857702 DOI: 10.1016/j.watres.2016.03.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 02/23/2016] [Accepted: 03/01/2016] [Indexed: 05/24/2023]
Abstract
In this study, we investigated the prevention of enzymatic urea hydrolysis in fresh urine by increasing the pH with calcium hydroxide (Ca(OH)2) powder. The amount of Ca(OH)2 dissolving in fresh urine depends significantly on the composition of the urine. The different urine compositions used in our simulations showed that between 4.3 and 5.8 g Ca(OH)2 dissolved in 1 L of urine at 25 °C. At this temperature, the pH at saturation is 12.5 and is far above the pH of 11, which we identified as the upper limit for enzymatic urea hydrolysis. However, temperature has a strong effect on the saturation pH, with higher values being achieved at lower temperatures. Based on our results, we recommend a dosage of 10 g Ca(OH)2 L(-1) of fresh urine to ensure solid Ca(OH)2 always remains in the urine reactor which ensures sufficiently high pH values. Besides providing sufficient Ca(OH)2, the temperature has to be kept in a certain range to prevent chemical urea hydrolysis. At temperatures below 14 °C, the saturation pH is higher than 13, which favors chemical urea hydrolysis. We chose a precautionary upper temperature of 40 °C because the rate of chemical urea hydrolysis increases at higher temperatures but this should be confirmed with kinetic studies. By considering the boundaries for pH and temperature developed in this study, urine can be stabilized effectively with Ca(OH)2 thereby simplifying later treatment processes or making direct use easier.
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Affiliation(s)
- Dyllon G Randall
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland.
| | - Manuel Krähenbühl
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | - Isabell Köpping
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | - Tove A Larsen
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | - Kai M Udert
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland.
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12
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Radjenovic J, Sedlak DL. Challenges and Opportunities for Electrochemical Processes as Next-Generation Technologies for the Treatment of Contaminated Water. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:11292-302. [PMID: 26370517 DOI: 10.1021/acs.est.5b02414] [Citation(s) in RCA: 441] [Impact Index Per Article: 49.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Electrochemical processes have been extensively investigated for the removal of a range of organic and inorganic contaminants. The great majority of these studies were conducted using nitrate-, perchlorate-, sulfate-, and chloride-based electrolyte solutions. In actual treatment applications, organic and inorganic constituents may have substantial effects on the performance of electrochemical treatment. In particular, the outcome of electrochemical oxidation will depend on the concentration of chloride and bromide. Formation of chlorate, perchlorate, chlorinated, and brominated organics may compromise the quality of the treated effluent. A critical review of recent research identifies future opportunities and research needed to overcome major challenges that currently limit the application of electrochemical water treatment systems for industrial and municipal water and wastewater treatment. Given the increasing interest in decentralized wastewater treatment, applications of electrolytic systems for treatment of domestic wastewater, greywater, and source-separated urine are also included. To support future adoption of electrochemical treatment, new approaches are needed to minimize the formation of toxic byproducts and the loss of efficiency caused by mass transfer limitations and undesired side reactions. Prior to realizing these improvements, recognition of the situations where these limitations pose potential health risks is a necessary step in the design and operation of electrochemical treatment systems.
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Affiliation(s)
- Jelena Radjenovic
- Catalan Institute for Water Research (ICRA) , Scientific and Technological Park of the University of Girona, 17003 Girona, Spain
- Advanced Water Management Centre, The University of Queensland , St Lucia, Queensland 4072, Australia
| | - David L Sedlak
- Department of Civil and Environmental Engineering, University of California , Berkeley, California 94720-1710, United States
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13
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Li H, Yu Q, Yang B, Li Z, Lei L. Electro-catalytic oxidation of artificial human urine by using BDD and IrO2 electrodes. J Electroanal Chem (Lausanne) 2015. [DOI: 10.1016/j.jelechem.2014.11.018] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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14
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Cho K, Hoffmann MR. Urea degradation by electrochemically generated reactive chlorine species: products and reaction pathways. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:11504-11. [PMID: 25219459 DOI: 10.1021/es5025405] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
This study investigated the transformation of urea by electrochemically generated reactive chlorine species (RCS). Solutions of urea with chloride ions were electrolyzed using a bismuth doped TiO2 (BiOx/TiO2) anode coupled with a stainless steel cathode at applied anodic potentials (Ea) of either +2.2 V or +3.0 V versus the normal hydrogen electrode. In NaCl solution, the current efficiency of RCS generation was near 30% at both potentials. In divided cell experiments, the pseudo-first-order rate of total nitrogen decay was an order of magnitude higher at Ea of +3.0 V than at +2.2 V, presumably because dichlorine radical (Cl2(-)·) ions facilitate the urea transformation primary driven by free chlorine. Quadrupole mass spectrometer analysis of the reactor headspace revealed that N2 and CO2 are the primary gaseous products of the oxidation of urea, whose urea-N was completely transformed into N2 (91%) and NO3(-) (9%). The higher reaction selectivity with respect to N2 production can be ascribed to a low operational ratio of free available chlorine to N. The mass-balance analysis recovered urea-C as CO2 at 77%, while CO generation most likely accounts for the residual carbon. In light of these results, we propose a reaction mechanism involving chloramines and chloramides as reaction intermediates, where the initial chlorination is the rate-determining step in the overall sequence of reactions.
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Affiliation(s)
- Kangwoo Cho
- Linde+Robinson Laboratories, California Institute of Technology , Pasadena, California 91125, United States
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Chen S, Shi Y, Wang W, Li Z, Gao J, Bao K, Han R, Zhang R. Phosphorus Removal from Continuous Phosphate-Contaminated Water by Electrocoagulation using Aluminum and Iron Plates Alternately as Electrodes. SEP SCI TECHNOL 2014. [DOI: 10.1080/01496395.2013.872145] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Vasudevan S. Effects of alternating current (AC) and direct current (DC) in electrocoagulation process for the removal of iron from water. CAN J CHEM ENG 2011. [DOI: 10.1002/cjce.20625] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Vasudevan S, Lakshmi J, Sozhan G. Studies Relating to Removal of Arsenate by Electrochemical Coagulation: Optimization, Kinetics, Coagulant Characterization. SEP SCI TECHNOL 2010. [DOI: 10.1080/01496391003775949] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Removal of iron from drinking water by electrocoagulation: Adsorption and kinetics studies. KOREAN J CHEM ENG 2010. [DOI: 10.1007/s11814-009-0176-9] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Vasudevan S, Sozhan G, Ravichandran S, Jayaraj J, Lakshmi J, Sheela M. Studies on the Removal of Phosphate from Drinking Water by Electrocoagulation Process. Ind Eng Chem Res 2008. [DOI: 10.1021/ie0714652] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | - Ganapathy Sozhan
- Central Electrochemical Research Institute (CSIR), Karaikudi 630 006, India
| | | | - Jeganathan Jayaraj
- Central Electrochemical Research Institute (CSIR), Karaikudi 630 006, India
| | | | - Margrat Sheela
- Central Electrochemical Research Institute (CSIR), Karaikudi 630 006, India
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