Thermochemical Treatment of Sewage Sludge Ash (SSA)—Potential and Perspective in Poland

Marzena Smol, Christian Adam and Stefan Anton Kugler
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Marzena Smol: Mineral and Energy Economy Research Institute, Polish Academy of Sciences, Wybickiego 7A str., 31-261 Krakow, Poland
Christian Adam: Bundesanstalt für Materialforschung und -prüfung (BAM), Zweiggelände Adlershof, Richard-Willstätter-Straße 11, 12489 Berlin, Germany
Stefan Anton Kugler: Bundesanstalt für Materialforschung und -prüfung (BAM), Zweiggelände Adlershof, Richard-Willstätter-Straße 11, 12489 Berlin, Germany

Energies, 2020, vol. 13, issue 20, 1-17

Abstract: Phosphorus (P) recovery from sewage sludge ash (SSA) is one of the most promising approaches of phosphate rock substitution in mineral fertilizers and might be a sustainable way to secure supply of this raw material in the future. In the current investigation, the process of thermochemical treatment of SSA was applied to SSA coming from selected mono-incineration plants of municipal sewage sludge in Poland (Cracow, Gdansk, Gdynia, Lodz, Kielce and Szczecin). The Polish SSA was thermochemically converted in the presence of sodium (Na) additives and a reducing agent (dried sewage sludge) to obtain secondary raw materials for the production of marketable P fertilizers. The process had a positive impact on the bioavailability of phosphorus and reduced the content of heavy metals in the obtained products. The P solubility in neutral ammonium citrate, an indicator of its bioavailability, was significantly raised from 19.7–45.7% in the raw ashes and 76.5–100% in the thermochemically treated SSA. The content of nutrients in the recyclates was in the range of 15.7–19.2% P 2 O 5 , 10.8–14.2% CaO, 3.5–5.4% Na 2 O, 2.6–3.6% MgO and 0.9–1.3% K 2 O. The produced fertilizer raw materials meet the Polish norms for trace elements covered by the legislation: the content of lead was in the range 10.2–73.1 mg/kg, arsenic 4.8–22.7 mg/kg, cadmium 0.9–2.8 mg/kg and mercury <0.05 mg/kg. Thus, these products could be potentially directly used for fertilizer production. This work also includes an analysis of the possibilities of using ashes for fertilizer purposes in Poland, based on the assumptions indicated in the adopted strategic and planning documents regarding waste management and fertilizer production.

Keywords: sewage sludge (SS); sewage sludge ash (SSA); critical raw materials (CRMs); phosphorus (P); fertilizer (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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