Type of Document Dissertation Author Diz, Harry Richard Author's Email Address firstname.lastname@example.org URN etd-81697-135443 Title Chemical and Biological Treatment of Acid Mine Drainage for the Removal of Heavy Metals and Acidity Degree PhD Department Civil Engineering Advisory Committee
Advisor Name Title Cherry, Donald S. Knocke, William R. Love, Nancy G. Rimstidt, james Donald Novak, John T. Committee Chair Keywords
- iron biooxidation
- iron precipitation
- iron removal technology
- acid mine drainage
Date of Defense 1997-08-11 Availability unrestricted AbstractThis dissertation reports the design of a process (patent
pending) to remove iron from acid mine drainage (AMD)
without the formation of metal hydroxide sludge. The
system includes the oxidation of ferrous iron in a packed
bed bioreactor, the precipitation of iron within a
fluidized bed, the removal of manganese and heavy metals
(Cu, Ni, Zn) in a trickling filter at high (>9) pH, with
final neutralization in a carbonate bed. The technique
avoided the generation of iron oxyhydroxide sludge.
In the packed bed bioreactor, maximum substrate oxidation
rate (R,max) was 1500 mg L-1 h-1 at dilution rates of 2
h-1, with oxidation efficiency at 98%. The half-saturation
constant (similar to a Ks) was 6 mg L-1. The oxidation
rate was affected by dissolved oxygen below 2 mg L-1, with
a Monod-type Ko for DO of 0.33 mg L-1. Temperature had a
significant effect on oxidation rate, but pH (2.0 to 3.25)
and supplemental CO2 did not affect oxidation rates.
Iron hydroxide precipitation was not instantaneous when
base was added at a OH/Fe ratio of less than 3. Induction
time was found to be a function of pH, sulfate
concentration and iron concentration, with a multiple R2
of 0.84. Aqueous [Al (III)] and [Mn (II)] did not
significantly (a = 0.05) affect induction time over the
range of concentrations investigated.
When specific loading to the fluidized bed reactor exceeded
0.20 mg Fe m-2 h-1, dispersed iron particulates formed
leading to a turbid effluent. Reactor pH determined the
minimum iron concentration in the effluent, with an optimal
at pH 3.5. Total iron removals of 98% were achieved in
the fluidized bed with effluent [Fe] below 10 mg L-1.
Further iron removal occurred within the calcium carbonate
Heavy metals were removed both in the fluidized bed reactor
as well as in the trickling filter. Oxidation at pH >9
caused manganese to precipitate (96% removal); removals of
copper, nickel, and zinc were due primarily to sorption
onto oxide surfaces. Removals averaged 97% for copper,
70% for nickel and 94% for zinc.
The treatment strategy produced an effluent relatively
free of iron (< 3 mg/L), without the formation of iron
sludge and may be suitable for AMD seeps, drainage from
acidic tailings ponds, active mine effluent, and acidic
iron-rich industrial wastewater.
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