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Alkaline Dehydration of Human Urine Collected in Source-Separated Sanitation Systems Using Magnesium Oxide

Simha, Prithvi and Friedrich, Christopher and Randall, Dyllon Garth and Vinnerås, Björn (2021). Alkaline Dehydration of Human Urine Collected in Source-Separated Sanitation Systems Using Magnesium Oxide. Frontiers in Environmental Science. 8 , 619901
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Abstract

Fresh human urine, after it is alkalized to prevent the enzymatic hydrolysis of urea, can be dehydrated to reduce its volume and to produce a solid fertilizer. In this study, we investigated the suitability of MgO to alkalize and dehydrate urine. We selected MgO due to its low solubility (<2 g.L-1) and relatively high saturation pH (9.9 +/- 0.2) in urine. Using a laboratory-scale setup, we dehydrated urine added to pure MgO and MgO mixed with co-substrates (biochar, wheat bran, or calcium hydroxide) at a temperature of 50 degrees C. We found that, dehydrating urine added to a mixture of MgO (25% w/w), biochar, and wheat bran resulted in a mass reduction of >90% and N recovery of 80%, and yielded products with high concentrations of macronutrients (7.8% N, 0.7% P and 3.9% K). By modeling the chemical speciation in urine, we also showed that ammonia stripping rather than urea hydrolysis limited the N recovery, since the urine used in our study was partially hydrolyzed. To maximize the recovery of N during alkaline urine dehydration using MgO, we recommend treating fresh/un-hydrolysed urine a temperature <40 degrees C, tailoring the drying substrate to capture NH4+ as struvite, and using co-substrates to limit the molecular diffusion of ammonia. Treating fresh urine by alkaline dehydration requires only 3.6 kg MgO cap(-1)y(-1) and a cost of US$ 1.1 cap(-1)y(-1). Therefore, the use of sparingly soluble alkaline compounds like MgO in urine-diverting sanitation systems holds much promise.

Authors/Creators:Simha, Prithvi and Friedrich, Christopher and Randall, Dyllon Garth and Vinnerås, Björn
Title:Alkaline Dehydration of Human Urine Collected in Source-Separated Sanitation Systems Using Magnesium Oxide
Series Name/Journal:Frontiers in Environmental Science
Year of publishing :2021
Volume:8
Article number:619901
Number of Pages:9
Publisher:FRONTIERS MEDIA SA
ISSN:2296-665X
Language:English
Publication Type:Journal article
Article category:Scientific peer reviewed
Version:Published version
Copyright:Creative Commons: Attribution 4.0
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 2 Engineering and Technology > 208 Environmental Biotechnology > Water Treatment
Keywords:ammonia, fertilizer, nitrogen recycling, urine source separation, wastewater, urine dehydration, sanitation, MgO
URN:NBN:urn:nbn:se:slu:epsilon-p-110779
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-110779
Additional ID:
Type of IDID
DOI10.3389/fenvs.2020.619901
Web of Science (WoS)000613912600001
ID Code:22664
Faculty:NJ - Fakulteten för naturresurser och jordbruksvetenskap
Department:(NL, NJ) > Dept. of Energy and Technology
Deposited By: SLUpub Connector
Deposited On:25 Feb 2021 13:43
Metadata Last Modified:25 Feb 2021 13:51

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