Controls and rates of acid production in commercial-scale sulphur blocks
Date
2009-12
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Degree Level
Doctoral
Abstract
The controls of water and O2 availability, microbial activity and temperature on acid (H2SO4) production rates in commercial-scale sulphur (S0) blocks were quantified and recommendations were made for minimizing H2SO4 production in S0 blocks. Acidic drainage from the S0 blocks (pH 0.4-1.0) was attributed to mixing of fresh infiltrating water and low-pH resident water (mean pH=-2.1) with resident water comprising ~4-8% of the drainage. Although clean S0 is strongly hydrophobic, preferential water infiltration occurred rapidly through fractured S0 blocks in which the bulk hydraulic conductivity was estimated to be similar to gravel or clean sand (Ks=1x10-1 to 1x10-3 m/s). Microbial colonization of fracture faces generated localized hydrophilic conditions that helped create preferential pathways for water infiltration. Liquid water contact (compared to water vapour) was essential for S0 oxidation (i.e., H2SO4 production), therefore H2SO4 production in the S0 blocks was limited to fractures and friable S0 through which water flowed. H2SO4 production was greatest in the upper 1 m of the S0 block (70 to >97% of annual H2SO4 production) and the result of autotrophic microbial S0 oxidation.
S0 oxidation rates were very sensitive to temperature and increased by a factor of 4.3 for a temperature increase of 10°C (Q10). Therefore minimizing temperature (1 vol.%, the total mass production rate of H2SO4 is approximately proportional to the O2 concentration at the surface of the S0 block (assuming in situ O2 concentrations decrease to
Description
Keywords
transport, reaction, geochemistry, acid, sulphur, storage, gas
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
College of Arts and Science
Program
College of Arts and Science