Title: Optimisation of nutrients and metals release from municipal sewage sludge by chemical extraction using Box-Behnken design

Authors: Ayla Uysal; Dilara Tuncer

Addresses: Department of Environmental Engineering, Suleyman Demirel University, Isparta, Turkey ' Department of Environmental Engineering, Suleyman Demirel University, Isparta, Turkey

Abstract: In this study, H₂SO₄ and citric acid using Box-Behnken design were utilised in order to release the nutrients and metals fixed in the anaerobic digested and dewatered sludge. For the dewatered sludge, release of 16.27 mg/L P and 120.74 mg/L NH₄⁺ were obtained at optimised conditions with citric acid 0.3 M, H₂SO₄ 6% and reaction time 105 min, respectively. For the digested sludge, release of 764.1 mg/L P and 388.3 mg/L NH₄⁺ were achieved at optimised conditions with citric acid 0.1 M, H₂SO₄ 6% and reaction time 180 min, respectively. In all experimental conditions, Fe and Zn were released together with nutrients. For digested sludge, a minimum Fe and Zn release was achieved at optimised conditions with citric acid 0.5 M, H₂SO₄ 2% and reaction time 105 min, respectively. Thus, this test conditions are thought to be more appropriate for the nutrients recovery from digested sludge.

Keywords: Box-Behnken design; dewatered sludge; digested sludge; metals release; nutrients; nutrient recovery; optimisation; municipal sewage sludge; chemical extraction; H2SO4; sulphuric acid; citric acid; anaerobic digestion; iron; zinc.

DOI: 10.1504/IJGW.2017.082778

International Journal of Global Warming, 2017 Vol.11 No.3, pp.317 - 327

Received: 29 Sep 2014
Accepted: 21 Jul 2015
Published online: 12 Mar 2017 *

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