of urea degrading bacteria was originated from natural
water (Chaophraya River, Thailand), where the
bacterial community is mixed cultures.
Biocemented sand reactors (SRs) were made of
plastic containers with dimensions of 80mm x 80mm x
80mm (width x length x height). The reactors were
placed with free-drop 250 g of sieved sand (sand
sample passed no. 100 and retained no. 200) with an
approximate depth of 40 mm and filled with 300 mL of
nutrient solution contained 250mM of urea, 250mM of
calcium ion (by CaCl2), and glucose (C6H12O6) of
1.5mM. Source of water used for preparing the
solution was collected from Northern part of
Chaophraya River. Control reactor was made of sand
sample mixed with only water. The experiment was
performed in ambient with average temperature of 25 ±
2 oC. The water level of each reactor was remarked. An
addition of deionized water to each BSR was
sometimes needed to maintain the constant level of
water table and prevent the level falling due to water
loss by evaporation.
Treated sands (SR1) and control (SR2) were
measured for strength development by bender element
test. Dried sand samples were collected for observing
the morphology by SEM and analyzed by XRD for
identifying the presence of CaCO3 precipitation in
treated sand. Effluent water was sampled and analyzed
for NH4
+ production and water pH. These parameters
were conducted through the period of the experiment
and the analyses were based on the procedures of
Standard Methods for the Examination of Water and
Wastewater [41].
4.1 X-ray diffraction
Fig. 5 illustrates the different patterns of X-ray
diffractogram between treated sand (SR1) and control
sand (SR2). The different peaks between the typical
sand and the treated sand in comparison with
precipitated CaCO3 powder obtained from the water
evaporation of solution are marked by “symbol ▲”
while the “symbol ●” marked the increment of
chemical compositions in sand samples from SR1 and
SR2.
Fig. 5. Pattern differences of X-ray diffraction between
typical sand and treated sand after biocementation
(“▲” indicates the precipitated CaCO3 in sand and
“●” indicates the increment of further chemical
compositions).