Environmental Engineering Reference
In-Depth Information
2.5.2 Biocementation Based on Production of Carbonates
by Heterotrophic Bacteria During Aerobic or Anoxic
Oxidation of Organics
Precipitation of calcium carbonate can be due to increase pH and production of
carbonate by heterotrophic bacteria during aerobic oxidation of organics (Ehrlich
1999 ; Wright and Oren 2005 ), for example, in such biogeochemical reactions as
ð
CH 3 COO
Þ 2 Ca þ 4O 2 ! CaCO 3 3CO 2 3H 2 O :
ð 2 : 7a Þ
Calcium carbonate precipitation due to oxidation of organics was used for
biocementation of the porous stones (Rodriguez-Navarro et al. 2003 ; Jimenez-
Lopez et al. 2008 ).
Dissolved salts or chelates of Fe(II) produced by iron-reducing bacteria under
strong anaerobic conditions can be also transformed to ferrous carbonate by
anaerobic heterotrophic bacteria:
ð
CH 3 COO
Þ 2 Fe þ 4O 2 ! FeCO 3 3CO 2 3H 2 O :
ð 2 : 7b Þ
Precipitation of calcium carbonate due to increase pH and production of car-
bonate by heterotrophic bacteria during anoxic oxidation of organics, for example
due to bioreduction of nitrate:
Þ 2 Ca þ 8 = 5NO 3 ! CaCO 3 # þ 4 = 5N 2 3CO 2
3H 2 O þ 8 = 5OH
ð
CH 3 COO
ð 2 : 8 Þ
Calcium carbonate precipitation due to nitrate bioreduction of organics is useful
for the combination of biocementation with nitrogen gas production in situ during
partial desaturation of sandy soil, which is an effective method for the mitigation
of earthquake-caused soil liquefaction (Chu et al. 2009a ; Rebata-Landa and
Santamarina 2012 ; He et al. 2013 ). Bioreduction of nitrate (bacterial denitrification
process) can also increase pH and initiate precipitation of CaCO 3 without pH
buffering (Hamdan et al. 2011 ). For example, precipitation of CaCO 3 can be
performed using bioreduction of calcium nitrate by ethanol:
12 NO 3 þ 5C 2 H 5 OH ! 6N 2 10 CO 2 9H 2 O þ 12 OH ;
ð 2 : 9 Þ
6Ca 2 þ þ 12 OH þ 6CO 2 ! 6 CaCO 3 6H 2 O,
ð 2 : 10 Þ
12 NO 3 þ 5C 2 H 5 OH þ 6Ca 2 þ ! 6 CaCO 3 6N 2 4CO 2
15 H 2 O :
ð 2 : 11 Þ
The biogeochemical reactions in case of denitrification and iron-based bio-
clogging are similar:
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