Sewage-sludge incineration ash secondary resource
Ash from thermal treatment of sewage sludge, distinct from unburned sludge, municipal-solid-waste incineration ash and coal fly ash. It is a heterogeneous secondary resource rather than a phosphate mineral species or individual critical element. The selected ash-B feed has unresolved fly/bottom fraction and host phases. Its source also supplies the separate municipal-waste ash and niobium records; those are linked views of one study, not additional experiments.
Microbial & Biochemical Mechanisms (1)
Limited and condition-dependent metal release from sewage-sludge ash
bioleaching
Microbial
The sludge-derived culture assay reports modest niobium release in all three conditions and a higher indium release only in the aerated 24 degrees C condition. These source-level observations remain qualified by undefined controls and analytical fractions; they are not a demonstrated recovery process for every sewage-sludge ash.
Experimental Context & Analytical Limits:
A living mixed culture derived from municipal activated sludge was adapted at 24 degrees C and 120 rpm in sludge:distilled water 1:1 with 1% powdered sulfur (percentage basis unspecified), until pH below 3 and reported sulfur-oxidizer index 10^-6. Each 300 mL flask contained 150 mL culture and 10 g ash for five days. Taxa, strains, treatment-plant identity, ash mineralogy, particle size, sterilization and detailed provenance are unresolved. Table 2 defines three variants: 24 degrees C/120 rpm without compressed air; 24 degrees C with air providing mixing; and 37 degrees C/50 rpm without compressed air. Three corresponding controls were averaged because their results were reportedly similar. ICP-OES measured metal content. This is a laboratory flask assay. Initial ash-B contents were 15.3 mg/kg Nb, 120.0 mg/kg In and 43.3 mg/kg Rh. Starting pH below 3 rose to 9, 8 and 9 in variants 1-3.
A living mixed culture derived from municipal activated sludge was adapted at 24 degrees C and 120 rpm in sludge:distilled water 1:1 with 1% powdered sulfur (percentage basis unspecified), until pH below 3 and reported sulfur-oxidizer index 10^-6. Each 300 mL flask contained 150 mL culture and 10 g ash for five days. Taxa, strains, treatment-plant identity, ash mineralogy, particle size, sterilization and detailed provenance are unresolved. Table 2 defines three variants: 24 degrees C/120 rpm without compressed air; 24 degrees C with air providing mixing; and 37 degrees C/50 rpm without compressed air. Three corresponding controls were averaged because their results were reportedly similar. ICP-OES measured metal content. This is a laboratory flask assay. Initial ash-B contents were 15.3 mg/kg Nb, 120.0 mg/kg In and 43.3 mg/kg Rh. Starting pH below 3 rose to 9, 8 and 9 in variants 1-3.
Curated Evidence Points:
Figures 6-8 report ash-B Nb release of 14.6%, 14.5% and 14.7% versus 5.9% averaged control; In release 10.2%, 53.1% and 3.5% versus 3.4% control; and Rh release 20.3%, 10.6% and 8.3% versus 4.1% control. The formula on p.74 normalizes leaching-culture metal concentration times volume to measured initial ash inventory. These reported percentages are not purified-product yields. The 37 degrees C indium result is numerically near the averaged control without a statistical test of equivalence.
Methods do not define control composition, inoculum exclusion, sterilization or matched acidity. Filtration/centrifugation, leach-sample digestion, culture-background subtraction and detection limits are unspecified, so dissolved metal cannot be distinguished confidently from colloidal/particulate material or sludge contributions. Three instrument exposures are not evidence of independent biological triplicates; replicate counts, error bars and statistical tests are absent. Table 4 calls variant 3 120 rpm while Table 2 and figures say 50 rpm. Its caption ambiguously mentions culture while running text defines released amount per kg waste. No phase-specific dissolution, isolated product purity, closed mass balance or industrial deployment was shown.
Table 4 labels the ash-B rhodium row Rd, which is not a valid element symbol; Figures 6 and running text use rhodium, and the inconsistency is retained rather than adopting an Rd identity. Ash-B niobium remains far below the ash-A shaken result despite the common culture preparation, so ash-A complete-release wording cannot be transferred. Table 1 dashes for Cd and Cr do not establish analytically proven absence or zero concentration. Alkalinity and unspecified mineral hosts constrain chemical interpretation.
Sources & References
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andrzejewska_gorecka_2019: Andrzejewska-Gorecka et al. (2019). Release of critical metals from furnace wastes using the process of bioleaching in various variants. Archives of Environmental Protection 45(3):72-78. DOI 10.24425/aep.2019.128643; research methods pp.73-74, Tables 1-4, Figures 1-9.
https://doi.org/10.24425/aep.2019.128643 (accessed 2026-10-11)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-11T09:26:04.474425+00:00 |
Codex (GPT-6; Codex) | CREATE | Created the distinct secondary-resource identity and source-scoped laboratory evidence, preserving control, measurement, scale and source-consistency limitations. |
Record source: data/records/sewage-sludge-incineration-ash.yaml