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Flue-gas-desulfurization wastewater secondary resource

Liquid residual streams generated by wet flue-gas desulfurization and associated wastewater treatment, distinct from solid FGD gypsum, coal ash, elemental selenium and natural mineral resources. The accepted experiment concerns a particular coal-power-plant effluent after physical/chemical pretreatment and dilution, not an invariant composition or all FGD streams. Its selenium-bearing residuals were investigated for treatment; no marketable recovered selenium product or inherited criticality is asserted.

Microbial & Biochemical Mechanisms (1)

Pilot biological treatment associated with selenium removal and sustained performance loss

separation Microbial

An activated-sludge membrane bioreactor followed by two inoculated granular-activated-carbon biofilters lowered selenium concentrations in pretreated FGD wastewater. The authors interpret removal as biological oxyanion reduction followed by solids retention, but the pilot lacks a matched sterile treatment train and direct characterization of its retained selenium phase. Partial removal persisted after performance deteriorated; stable attainment of the source-defined treatment target was not demonstrated.

Experimental Context & Analytical Limits:
Pleasant Prairie Power Plant, Wisconsin, burning Powder River Basin subbituminous coal; pilot operation October 2015–March 2016. Full-scale lime/clarification, organosulfide and ferric/polymer treatment preceded 1:1 volume blending with untreated Lake Michigan service water. Municipal mixed liquor from Kenosha seeded the MBR; GE supplied the ABMet inoculum, without taxon or strain resolution. Living suspended biomass and attached biofilms were supplied acetic-acid-based nutrients, with recipes changed and molasses introduced late. The MBR had anoxic/aerobic/anoxic zones, a reported operating pH control range 6.8–7.2 and ultrafiltration. Each downstream ABMet stage contained 1,270 L of GAC. Total ABMet empty-bed contact time was 18.8 h in Condition 2 and 12.4 h in Conditions 3–4; the commercial target near 8 h was not reached. The source describes several simultaneous nutrient, flow, cleaning and chemical adjustments, not controlled causal contrasts. This was a real-feed pilot, not proof of successful full-scale performance or isolated-product recovery.
Curated Evidence Points:
Chapters 2–3, Figures 2-1 and 3-1, Tables 3-1/3-2 and 4-4 establish the feed pretreatment, dilution, inoculated reactors and operation. Table 5-1 reports Condition 2 average total selenium concentrations of 1,071 micrograms/L in blended pilot influent, 173 in MBR effluent and 5 in final ABMet effluent. These are stage concentration summaries, not a flow-normalized mass recovery or isolated selenium yield. Figure 2-4 is a supplier illustration of ABMet bacteria and particles, not demonstrated phase characterization of this pilot product.
Tables 4-7/5-1 and Figures 4-11/4-13 report final total-selenium means of 36 and 21 micrograms/L in Conditions 3 and 4, exceeding the study's 6 micrograms/L target. That target was tied to the report's historical 2015 benchmark and dilution; no current regulatory claim is made. The first elevated sample preceded the flow increase on the same day, so shortened contact time alone is not established as the cause. Sulfate-reducer competition, inhibitory constituents and nutrient effects remain hypotheses. Figures 4-2/4-3 also preserve lost nitrification despite continued denitrification; this is not uniform biological treatment success.
Table 4-8 and Appendix B document falsely low selenium analyses and subsequent peroxide-assisted reanalysis: initial total values 13, 11 and 8.2 micrograms/L on January 18, 19 and 21, 2016 became 15, 22 and 31. Table B-2 retains unreconciled total/dissolved/species results, including a January 28 sum of dissolved species of 135.4 micrograms/L versus reported total 17.0 and dissolved 9.28 at the same laboratory. Reported dissolution fractions and mechanistic speciation must therefore remain qualified; these results do not establish a complete selenium balance.
S7 selenium qc rows 31–46 preserve initial assays, poor matrix-spike recovery and peroxide re-digestion results, including the January 19 corrected value 22 that is omitted from Table B-1's selected preparation rows but present in Table 4-8. The workbook supports the analytical correction lineage, not an additional independent experiment. No bulk concentration import or reconstructed percent recovery is made.
Table 4-6 reports selenium in backwash liquid, much of it assigned to the dissolved fraction, and flags unexpectedly low suspended solids as possible sampling error. Such residual measurements do not prove collection of pure elemental selenium. Sections 3-7 and 5-1/5-2 describe pilot waste returning to the absorber and failure to sustain the desired selenium endpoint. The mechanism's reduction interpretation is retained as the authors' explanation rather than exclusive proof separating microbial reduction, sorption, chemical precipitation and filtration.

Sources & References

  1. epri_2017_pilot: EPRI (2017). Biological Treatment of Flue Gas Desulfurization Wastewater at a Power Plant Burning Powder River Basin Coal: Pilot Demonstration with the ABMet Technology. Final Report March 2017, report 3002006089. CH2M Hill primary pilot report; Chapters 1–5 and Appendices A–C.
    https://restservice.epri.com/publicdownload/000000003002006089/0/Product (accessed 2026-10-15)
  2. epri_2017_embedded_data: EPRI report 3002006089, Appendix C embedded original workbook: Worksheet in 3002006089_test.xlsx. Twenty sheets; especially S7 selenium qc, S7 ABMet 2nd stage effl and S7 Brooks Applied Labs. Same pilot lineage, not independent replication.
    https://restservice.epri.com/publicdownload/000000003002006089/0/Product (accessed 2026-10-15)

Curation History

Timestamp Curator Action Summary
2026-10-15T06:12:32Z Codex (GPT-6; Codex) CREATE Created a distinct liquid FGD wastewater resource with qualified primary pilot treatment evidence, source analytical corrections, unresolved selenium balance and explicit failure/scale limits.

Record source: data/records/flue-gas-desulfurization-wastewater.yaml