Cycles Gone Wild

Question 1

Microbial Corrosion

Answer 1

• chemolithoautotrophs
• metal and non-metalic materials
• aerobic (bac oxidize iron–> iron oxides + hydroxides or oxidize sulfur –> sulfuric acid) and anaerobic (ie. Sulfate-reducing bac–> hydrogen sulfide== sulfide stress cracking + form part of biofilm) env.

Question 2

Biogenic sulfide corrosion

Answer 2

• bac mediated process forming (1) hydrogen sulfide gas
  (2) sulfuric acid attacks concrete/steel matrix of wastewater pipes –> aerobic sulfide oxidation reaction == H2SO4
  (3) all within a biofilm (therefore there is an areobic and anaerobic) = anaerobic sulfate reduction (SRB)

–> pipes lead to cycling of sulfur

Question 3

Acid mine drainage

Answer 3

• AMD
  (1) pyrite (FeS2) is exposed to O2 and h2o == AMD w/ pH less then 2.0 therefore increases metal solubility
  (2) autooxidation and microbial oxidation of pyrite generates sulfuric acid (H2SO4)