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Comparison of Alum and Sulfuric Acid to Retain and Increase the Ammonium Content of Digestate Solids during Thermal Drying

1
School of Agriculture, Sun Yat-Sen University, Shenzhen 518107, China
2
Department of Plant and Environmental Science, Faculty of Science, University of Copenhagen, 1871 Frederiksberg, Denmark
*
Author to whom correspondence should be addressed.
Academic Editor: Germán Tortosa
Received: 7 April 2021 / Revised: 31 May 2021 / Accepted: 3 June 2021 / Published: 10 June 2021
Aluminum sulphate (alum, Al2(SO4)3·nH2O) has successfully been used to reduce ammonia loss from poultry litter, cattle feedlots and manure composting, but has not yet been utilized in the thermal drying process of digestate solids. The objectives of the present study were to evaluate the effects of alum addition on ammonium nitrogen (NH4+-N) content and phosphorus (P) solubility in dried digestate solids in comparison to the addition of concentrated sulfuric acid (H2SO4). Manure-based (MDS) and sewage sludge-based (SDS) digestate solids were chosen to conduct a drying experiment at four pH levels (original pH, 8.0, 7.5 and 6.5) and using two acidifying agents (alum, concentrated H2SO4). Alum addition increased the final NH4+-N content significantly from 1.4 mg g−1 in the non-acidified control up to 18 mg g−1 and 10.8 mg g−1 in dried MDS and SDS, respectively, which were higher levels than obtained with the addition of concentrated H2SO4. Moreover, alum considerably lowered the water extractable phosphorus (WEP) in raw and dried SDS by 37–83% and 48–72%, respectively, compared with the non-treated control. In contrast, concentrated H2SO4 notably increased WEP in raw and dried MDS by 18–103% and 29–225%, respectively. The comparison between the two acidifying agents indicated that alum had the potential to be an efficient and easy-handling alternative to concentrated sulfuric acid, resulting in higher NH4+-N content and lower P solubility. View Full-Text
Keywords: aluminum sulfate; ammonia loss; acidification; thermal drying; biosolids aluminum sulfate; ammonia loss; acidification; thermal drying; biosolids
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MDPI and ACS Style

Liu, J.; Jensen, L.S.; Müller-Stöver, D.S. Comparison of Alum and Sulfuric Acid to Retain and Increase the Ammonium Content of Digestate Solids during Thermal Drying. Nitrogen 2021, 2, 287-297. https://0-doi-org.brum.beds.ac.uk/10.3390/nitrogen2020019

AMA Style

Liu J, Jensen LS, Müller-Stöver DS. Comparison of Alum and Sulfuric Acid to Retain and Increase the Ammonium Content of Digestate Solids during Thermal Drying. Nitrogen. 2021; 2(2):287-297. https://0-doi-org.brum.beds.ac.uk/10.3390/nitrogen2020019

Chicago/Turabian Style

Liu, Jingna, Lars S. Jensen, and Dorette S. Müller-Stöver 2021. "Comparison of Alum and Sulfuric Acid to Retain and Increase the Ammonium Content of Digestate Solids during Thermal Drying" Nitrogen 2, no. 2: 287-297. https://0-doi-org.brum.beds.ac.uk/10.3390/nitrogen2020019

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