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Cho, Jaeweon
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Energy recovery through reverse electrodialysis: Harnessing the salinity gradient from the flushing of human urine

Author(s)
Volpin, FedericoWoo, Yun ChulKim, HankiFreguia, StefanoJeong, NamjoChoi, June-SeokCho, JaeweonPhuntsho, SherubShon, Ho Kyong
Issued Date
2020-11
DOI
10.1016/j.watres.2020.116320
URI
https://scholarworks.unist.ac.kr/handle/201301/49949
Fulltext
https://www.sciencedirect.com/science/article/pii/S0043135420308563?via%3Dihub
Citation
WATER RESEARCH, v.186, pp.116320
Abstract
Urine dilution is often performed to avoid clogging or scaling of pipes, which occurs due to urine's Ca2+ and Mg2+ precipitating at the alkaline conditions created by ureolysis. The large salinity gradient between urine and flushing water is, theoretically, a source of potential energy which is currently unexploited. As such, this work explored the use of a compact reverse electrodialysis (RED) system to convert the chem-ical potential energy of urine dilution into electric energy. Urine' composition and ureolysis state as well as solution pumping costs were all taken into account. Despite having almost double its electric conductivity, real hydrolysed urine obtained net energy recoveries E-Net of 0.053-0.039 kWh/m(3), which is similar to energy recovered from real fresh urine. The reduced performances of hydrolysed urine were linked to its higher organic fouling potential and possible volatilisation of NH3 due to its high pH. However, the higher-than-expected performance achieved by fresh urine is possibly due to the fast diffusion of uncharged urea to the freshwater side. Real urine was also tested as a novel electrolyte solution and its performance compared with a conventional K4Fe(CN)(6)/K3Fe(CN)(6) couple. While K4Fe(CN)(6)/K3Fe(CN)(6) outperformed urine in terms of power densities and energy recoveries, net chemical reactions seemed to have occurred in urine when used as an electrolyte solution, leading to TOC, ammonia and urea removal of up to 13%, 6% and 4.4%, respectively. Finally, due to the migration of K+, NH4+ and PO43-, the low concentration solution could be utilised for fertigation. Overall, this process has the potential of providing off-grid urine treatment or energy production at a household or building level. (c) 2020 Elsevier Ltd. All rights reserved.
Publisher
PERGAMON-ELSEVIER SCIENCE LTD
ISSN
0043-1354
Keyword (Author)
Reverse electrodialysisNutrients recoveryPower generationOxidationHuman urine
Keyword
PRESSURE-RETARDED OSMOSISELECTROCHEMICAL OXIDATIONPOWER-GENERATIONWATERELECTROOXIDATIONELECTROLYSISPERFORMANCEEFFICIENCYREDUCTIONMEMBRANES

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