1. Stephanie Lara1
, Travis Waller2
, Jacob Lanphere1
, Sharon Walker2
1
Natural Mathematics and Science Department, California Baptist University, Riverside, CA, USA
2
Department of Chemical and Environmental Engineering, University of California, Riverside, CA, USA
Abstract
Methods Discussion
Titanium dioxide (TiO2) NPs have been introduced to the environment by companies through products such as sunscreen, clothing, and as scratch resistant protective layers to some hard
surfaces in technology. We investigated a model colon and model septic tank to determine if these TiO2 NPs can be used to enhance water treatment systems for the improvement of water
quality. A model colon and model septic tank will be investigated in order to look at the effects and changes to the microbial community due to the addition of TiO2. Both food and industrial
grades of TiO2 NPs were added to the model colon and septic to determine if they produce a similar impact on microbial community of these two environments. To run thorough diagnostics,
the NPs will be run through the model colon seeded with a human microbial community to monitor interactions between with the gut bacteria and the introduced TiO2 . At this time, baseline
experiments have been conducted without the presence of TiO2 to understand the normal operating conditions of the model human colon and septic systems in which changes may occur
after the introduction of the TiO2 NPs. Better understanding of these NPs will result after the TiO2 NPs pass through the colon and enter the model septic tank where biological, chemical,
and physical conditions may then further alter the NPs impacting the overall quality of the septic tank effluent.
Overview
Future Work
Acknowledgments
• Characterization of food and industrial grade TiO2 within the
environment
• Further investigation of the biofilm (ICP-MS), septic effluent, and
sludge and the dissolution of TiO2
• Further examination of colon and septic impacts from TiO2 with
UV-light in septic system in addition to regular procedures from
the colon system
I would like to thank Dr. Walker for helping us throughout the
program. I would also like to express my appreciation to Dr.
Lanphere for his mentoring and support. I would like to express my
grattitude toward Travis Waller for his guidance and help
throughout this process. Finally, I would like to thank the Building
Bridges program funded by the US Department of Agriculture for
supporting my summer internship. I would also like to thank Maria
Franco-Aguilar for her leadership and support throughout the
Building Bridges program.
M T W Th F
0.00E+000
3.00E+009
6.00E+009
9.00E+009
1.20E+010
1.50E+010
1.80E+010
2.10E+010 Baseline
P25
FG
CellConcentration(Bacteria/mL)
Day
Figure 6: Weekly averages of bacteria
cell concentration in relation to baseline,
P25, and FG TiO2 Nanoparticle
conditions.
M T W Th F
4.0
4.5
5.0
5.5
6.0
6.5
7.0 Baseline
P25
FG
pH
Day
Figure 7: Weekly averages of pH in
relation to the baseline, P25, and FG
TiO2 Nanoparticle conditions.
M T W Th F
-28
-26
-24
-22
-20
-18
-16
Baseline
P25
FG
ZetaPotential(mV)
Day
Figure 5: Average Zeta Potential values
are shown for food grade (FG) and P25
TiO2 NPs over a five day period.
Environmental Effects Of Titanium Dioxide Nanoparticles Inside A Model Colon
M T W Th F
4
5
6
7
Baseline
P25
FG
Conductivity(mS/cm)
Day
Figure 8: Weekly averages of
conductivity in relation to the baseline,
P25, and FG TiO2 Nanoparticle
conditions
As a result of the increased applications of nanotechnology, TiO2 has
been introduced through food and different consumer products. To
understand the characteristics of a microbial community and TiO2,
interactions were monitored with an established baseline community. The
reason were to analyze (1) characterization; (2) septic tank water quality
measurements; and changes caused by TiO2 particles where the
systems will be identified. This research was performed to better
understand and potentially enhance water treatment methods within
septic tank systems.
Results to Date
To create a consistent human fecal microbial community, a model colon was created that feeds into the model septic tank. The baseline reacting factor for the microbial community will be
established with the two different types of NPs (1) industrial Nano TiO2 (P25) and (2) food grade TiO2 (FG) which will be independently added to the colon. Each of these trials will run at a
period of three weeks without particles to attain a solid baseline data, and once done so we will add the nanomaterials and run those for three weeks as well.
The colon was fed three times a day to mimic what would be regular human bowel movements. A pump circulates the Colon Media that consists of the donated fecal matter supplying the
microbial community and other materials that may be found in the colon during the transfer of bacteria from the colon to the septic system. The pump circulates the colon media through a
glass tube that consists of dialysis tubing inside in order for the colon media to be semi-permeable as it would be inside the human body. Different tests were ran throughout the week,
Monday-Friday to monitor the bacterial activity before the NPs get introduced.
Bacteria Characterization in Model Septic
•Nano TiO2 causes an increase in hydrophobicity and positive cell
surface charge (EPM) values.
•Electrophoretic Mobility (EPM): "The electrophoretic mobility is the
rate of migration of the substance measured in cm/s under the
influence of a potential gradient of 1 V/cm, and is expressed in
cm2·V-1·s-1" (The International Pharmacopoeia. 2006).
•Each TiO2 NP causes specific, rather than general effects to the
septic system, where baseline characteristics may indicate a
change due to the addition of TiO2 NPs
•TiO2 NPs may cause disruption in septic tank function during
specific weeks, potentially allowing only partial waste treatment like
in a previous study where Copper Nanoparticles (CuNPs) were
used and similar characteristics were being shown by the NPs (Lin,
Sijie, Alicia A. Taylor, Zhaoxia Ji, Chong Hyun Chang, Nichola M.
Kinsinger, William Ueng, Sharon L. Walker, and André E. Nel, 2015)
Figure 4: Estimated global mass flow of ENMs (in metric tons/year) from
production to disposal or release, considering high production and release
estimates as of 2010. (Keller and Lazareva, 2013)
Figure 1: Micron (software) and hemocytometer for
counting bacteria cell concentrations
Figure 2: The model colon reactor used in this study Figure 3: A human model of the colon