Abstract

Large amounts of phosphorus are present in organic waste, mainly in sewage sludge and animal by-products. Increasingly, the waste is incinerated and phosphorus ends up in the ash. Sustainable waste management requires the beneficial reuse of phosphorus present in such ash. The first necessary step when recovering phosphorus from ash is dissolution by acid. The objective of this study was to quantify the acid requirement for phosphorus dissolution from sewage sludge ash and animal carcass ash. Both the amount of acid applied and its concentration were varied. Furthermore, phosphorus dissolution was optimized by controlling the pH during acid addition. Elemental analysis of sewage sludge ash showed that it comprised 6-10% P, 7-18% Ca, 2-11% Fe and 3-9% Al. The elemental content of animal carcass ash was even higher: 18% P and 30% Ca. The amount of acid required to obtain 85% phosphorus dissolution from sludge ash was 0.39-0.78 kg H2SO4 kg-1 ash, depending on the total cation/phosphorus equivalent ratio. The amount required to obtain the highest possible P dissolution within two hours (73%) from animal carcass ash was 0.69 kg H2SO4 kg-1 ash. Lower amounts of sulphuric acid were required for P dissolution in ashes of sludge from a bio-P treatment process and animal carcass, compared with the theoretical acid requirement for apatite dissolution. Applying pH control during dissolution resulted in reduced acid consumption (20%) and enabled more than 85% phosphorus dissolution from sludge ash at pH 2.0 in the two-hour dissolution time.

Keywords

ash; phosphorus; sewage sludge; animal carcass; dissolution

Published in

Environmental Technology
2009, Volume: 30, number: 11, pages: 1215-1226
Publisher: TAYLOR & FRANCIS LTD

SLU Authors

• Cohen, Yariv

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

Sustainable Development Goals

Ensure sustainable consumption and production patterns


UKÄ Subject classification

Environmental Sciences


Publication identifier

DOI: https://doi.org/10.1080/09593330903213879

Permanent link to this page (URI)

https://res.slu.se/id/publ/49349