Extraction and precipitation of phosphorus from sewage sludge

Journal article

Authors/Editors

Ntuli, Freeman

Research Areas

No matching items found.

Publication Details

Author list: Shiba NC, Ntuli F

Publisher: Elsevier

Place: OXFORD

Publication year: 2017

Journal: Waste Management (0956-053X)

Journal acronym: WASTE MANAGE

Volume number: 60

Start page: 191

End page: 200

Number of pages: 10

ISSN: 0956-053X

Languages: English-Great Britain (EN-GB)

View in Web of Science | View on publisher site | View citing articles in Web of Science

Abstract

Raw sewage sludge from East Rand Water Care Association (ERWAT) had high phosphorus (P) content, approximately 15.2% (w/w) P2O5, which indicates a potential resource for the limiting nutrient. Leaching sewage sludge with 1 M sulphuric acid at 5% solid loading for 2 h resulted in an 82% phosphorus extraction. However, the phosphorus was recovered as iron phosphates, thus a further purification step using ion exchange to remove iron was required to increase the degree of P release. Magnesium oxide and ammonium hydroxide were used as magnesium and nitrogen sources, respectively, as well as pH regulators to precipitate P as struvite. 57% struvite was precipitated and the total phosphorus content of the precipitate was 25.9%. Kinetic studies showed that the leaching of phosphorus follows the Dickinson model for the first 100 min with a rate of reaction of about 2 x 10(-5) s(-1) The rate limiting step is controlled by diffusion. Phosphorus solubility in 2% critic acid was almost 96%, which is the amount of phosphorus available to plants if the precipitate is applied as a fertiliser. Environmental, gram-positive Bacillus subtilis were found in the precipitate, which are harmless to the environment since they already exist in the soil where the precipitate can be applied as a fertiliser. (C) 2016 Elsevier Ltd. All rights reserved.

Keywords

Phosphate fertiliser, Phosphorus extraction, Sewage sludge, Struvite precipitation

Documents