 |
| Titel |
Metals accumulations during thermal processing of sewage sludge - characterization of bottom ash and air pollution control (APC) residues |
| VerfasserIn |
Monika Kasina, Piotr R. Kowalski, Marek Michalik |
| Konferenz |
EGU General Assembly 2016
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250127051
|
| Publikation (Nr.) |
 EGU/EGU2016-6872.pdf |
|
|
|
|
|
| Zusammenfassung |
| Due to increasing mass of sewage sludge, problems in its management have appeared. Over
years sewage sludge was landfilled, however due to EU directives concerning environmental
issues this option is no longer possible. This type of material is considered hazardous due to
highly concentrated metals and harmful elements, toxic organic substances and
biological components (e.g. parasites, microbes). Currently in Europe, incineration
is considered to be the most reasonable method for sewage sludge treatment. As
a result of sludge incineration significant amount of energy is recovered due to
high calorific value of sewage sludge but bottom ash and APC residues are being
produced.
In this study we show the preliminary results of chemical and mineral analyses of both
bottom ash and APC residues produced in fluidized bed boiler in sewage sludge
incineration plant in Poland, with a special emphasis on metals which, as a part
of incombustible fraction can accumulate in the residual materials after thermal
processing.
The bottom ash was a SiO2-P2O5-Fe2O3-CaO-Al2O3 dominated material. Main mineral
phases identified in X-ray diffraction patterns were: quartz, feldspar, hematite, and
phosphates (apatite and scholzite). The bottom ash was characterized by high content of Zn -
4472 mg kg−1, Cu - 665.5 mg kg−1, Pb - 138 mg kg−1, Ni - 119.5 mg kg−1, and
interestingly high content of Au - 0.858 mg kg−1
The APC residues composition was dominated by soluble phases which represent more
than 90% of the material. The XRD patterns indicated thenardite, halite, anhydrite, calcite
and apatite as main mineral phases.
The removal of soluble phases by dissolution in deionised water caused a significant mass
reduction (ca. 3% of material remained on the filters). Calcite, apatite and quartz were main
identified phases. The content of metals in insoluble material is relatively high: Zn - 6326 mg
kg−1, Pb - 514.3 mg kg−1, Cu - 476.6 mg kg−1, Ni - 43.3 mg kg−1. The content of Cd,
As, Se and Hg was noted also what can be a reason of potential environmental
concerns.
A significant reduction of sludge volume after incineration causes concentration of
numerous elements in both types of residues. The removal of soluble fraction from APC
residues caused almost a 30-fold additional concentration of elements what makes this
material interesting in terms of metals recovery.
A detailed identification of metals occurrences and their distribution within
mineral phases will be of a great importance in determination of possibilities of their
recovery.
Acknowledgment: The study was supported by Polish Nacional Science Centre NCN
grant No UMO-2014/15/B/ST10/04171 |
|
|
|
|
|
|