Biological sulfuric acid transformation: Reactor design and process optimization
- Ciba-Geiby AG, Schweizerhalle (Switzerland)
- Univ. of Zurich (Switzerland)
As an alternative to the current disposal technologies for waste sulfuric acid, a new combination of recycling processes was developed. The strong acid (H[sub 2]SO[sub 4]) is biologically converted with the weak acid (CH[sub 3]COOH) into two volatile weak acids (H[sub 2]S, H[sub 2]CO[sub 3]) by sulfate-reducing bacteria. The transformation is possible without prior neutralization of the sulfuric acid. The microbially mediated transformation can be followed by physiocochemical processes for the further conversion of the H[sub 2]S. The reduction of sulfate to H[sub 2]S is carried out under carbon-limited conditions at pH 7.5 to 8.5. A fixed-bed biofilm column reactor is used in conjunction with a separate gas-stripping column which was installed in the recycle stream. Sulfate, total sulfide, and the carbon substrate (in most cases acetate) were determined quantitatively. H[sub 2]S and CO[sub 2] are continually removed by stripping with N[sub 2]. Optimal removal is achieved under pH conditions which are adjusted to values below the pK[sup a]-values of the acids. The H[sub 2]S concentrations in the stripped gas was 2% to 8% (v/v) if H[sub 2]SO[sub 4] and CH[sub 3]COOH are fed to the recycle stream just before the stripping column. Microbial conversion rates of 65 g of sulfate reduced per liter of bioreactor volume per day are achieved and bacterial conversion efficiencies for sulfate of more than 95% can be maintained if the concentration of undissociated dH[sub 2]S is kept below 40 to 50 mg/L. Porous glass spheres, lava beads, and polyurethane pellets are useful matrices for the attachment of the bacterial biomass. Theoretical aspects and the dependence of the overall conversion performance on selected process parameters are illustrated in the Appendix.
- OSTI ID:
- 6332087
- Journal Information:
- Biotechnology and Bioengineering; (United States), Journal Name: Biotechnology and Bioengineering; (United States) Vol. 41:3; ISSN BIBIAU; ISSN 0006-3592
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
320305 -- Energy Conservation
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63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
BACTERIA
BIODEGRADATION
BIOREACTORS
CHALCOGENIDES
CHEMICAL REACTIONS
DECOMPOSITION
DESIGN
FUZZY LOGIC
GROWTH
HYDROGEN COMPOUNDS
HYDROGEN SULFIDES
INORGANIC ACIDS
MATHEMATICAL LOGIC
MICROORGANISMS
OPTIMIZATION
OXYGEN COMPOUNDS
PACKED BEDS
PH VALUE
RECYCLING
SULFATE-REDUCING BACTERIA
SULFATES
SULFIDES
SULFUR COMPOUNDS
SULFURIC ACID