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Project
Experiments
Modeling
Prototype
Human Practices
Safety
About Us
Attributions
Project
Experiment
Modeling
Prototype
Human Practice
Biosafety
About Us
Attributions
hi
PROTOTYPE
It is estimated that about 95% of nanoparticles used in consumer products end up in wastewater (Kiser et al. 2009). Our goal is to apply our biofilm and Proteorhodopsin (PR) bacteria in wastewater treatment plants (WWTPs) to remove most nanoparticles (NPs) before the effluent is released into the environment.
WASTEWATER TREATMENT
When wastewater enters a plant, the first step is to remove coarse solids and large materials using a grit screen (figure___). The water can then be processed in three main stages: Primary, Secondary, and sometimes Tertiary Treatment (Pescod 1992). In Primary Treatment, heavy solids are removed by sedimentation, and floating materials (such as oils) can be taken out by skimming. However, dissolved materials and colloids—small, evenly dispersed solids such as nanoparticles—are not removed here (Pescod 1992). Secondary Treatment generally involves the use of aeration tanks, where aerobic microbes help to break down organic materials. This is also known as the activated sludge process (Davis 2005). In a subsequent sedimentation step, the microbes are removed and the effluent is disinfected (often by chlorine or UV) before it is released into the environment. In certain WWTPs, wastewater may go through Tertiary Treatment, an advanced process typically aimed to remove nitrogen and phosphorous, and assumed to produce an effluent free of viruses. However, Tertiary Treatment requires additional infrastructure that is expensive and complex, limiting its global usage (Pescod 1992; Malik 2014).
We plan to add our bacteria either in the deep aeration tanks or the secondary sedimentation tanks. The disinfection tank will kill the bacteria used in previous tanks.Figure: Christine C.
We plan to add our bacteria either in the deep aeration tanks or the secondary sedimentation tanks. The disinfection tank will kill the bacteria used in previous tanks.Figure: Christine C.
Biosafety
We have chosen to use a safe and common lab strain of E. coli, K-12, as our chassis (Environmental Protection Agency 1977). In both approaches, our constructs do not express proteins associated with virulence: PR is a membrane protein that commonly exists in marine bacteria, and for biofilm production we were careful to avoid known virulence factors such as alpha hemolysins (Fattahi et al. 2015). Most importantly, biosafety is built into WWTPs. Before treated effluent is released back into the environment, it must go through a final disinfection step, where chlorine, ozone, or UV radiation are used to kill microbes still present in the wastewater (Pescod 1992).
APPLYING PR IN WWTPs
Tap Water Museum
We visited the tap water museum hoping to find out more about how tap water is treated. We learned that water filtration methods vary in different areas of Taiwan, with Taipei’s filtration method being the simplest since the water is relatively clean compared to other regions, such as Kaohsiung, where the city is heavily industrialized. In Taipei, the source of tap water comes from a protected zone upstream of Xindian river. We also learned that they use sedimentation tanks and flocculation to help clump up and remove impurities. Due to the lack of a disinfection step, however, we realized that our project would not be applicable here, since our project depends on the use of E. coli bacteria. (Whole team activity)
Nanoparticle and Wastewater experts
Dr. Eric Lee
Before we started to conduct experiments, we emailed Dr. Eric P. Lee, senior member of technical staff at Maxim Integrated, and TAS alumnus, to ask him some general questions about our approach of our project. We told him about our two approaches, one with E. coli receptors that bind to the capping agents of nanoparticles, the other with biofilm that traps nanoparticles. Dr. Lee suggested that our membrane receptor must be specific to a particular capping agent. He also commented that the biofilm approach was a good idea since we could trap multiple types of nanoparticles regardless of their capping agent. (Interviewed by Emily C.)
Dr. Gwo-Dong Roam
We interviewed Professor Roam of National Central University and former general director of the Environmental Analysis Labs (EAL) of the Taiwan Environmental Protection Agency to learn more about the background and potential threat of nanoparticles. Dr. Roam informed us that the most common nanoparticles used in Taiwan include: TiO2, ZnO, Ag, Au, Fe, Carbon Nanotubes, Fullerenes, Clay, and Graphene. He also told us that the toxicity of a nanoparticle is directly related to its size, but there are currently no regulations or guidelines that specify the toxicity of different types and sizes of nanoparticle. With the increased use of nanoparticles in society, Dr. Roam believes that more attention should be placed on waste management, risk assessment and regulations.
After our first visit to the Dihua WWTP, we learned that the sludge removed from wastewater is either 1) sent to landfills, 2) used as fertilizer, or 3) incinerated. We asked Dr. Roam if sludge containing aggregated nanoparticles would still be harmful to the environment if disposed of using current methods. He said that all of these sludge disposal solutions are still harmful to the environment, but they are still better than letting nanoparticles flow into bodies of water. He advised us to target removal of nanoparticles in the wastewater treatment process before it is discharged. (Interviewed by Candice L. and Justin Y.)
Professor Gwo-Dong Roam (left) of National Central University and former general director of the Environmental Analysis Labs (EAL) of Taiwan EPA.
Materials that Dr. Roam provided the team with.
Thomas J. Brown
Thomas J. Brown, the Water Program Specialist of the Pennsylvania Department of Environmental Protection (DEP) occasionally helps with the Boswell Wastewater Treatment Plant. He has also worked with the EPA in Taiwan on wastewater treatments. We interviewed Mr. Brown about our methods to clean nanoparticles in wastewater treatment plants and how to achieve our goal of implementation. With his expertise in the field of wastewater treatment, he provided us some suggestions as to how we could turn our project into reality.
For example, we asked him if there were differences between rural and urban plants that we should take into consideration when thinking about implementing our project. He responded that the biological processes used for treatment remains the same regardless of facility size. This helped us think about and design our final prototype, which can potentially be used in both rural and urban treatment plants.
Nanoparticle Manufacturers and Disposal Services
Apex Nanotek
To learn more about the applications of nanoparticles, we visited a nanotech company that uses silver nanoparticles to make various antimicrobial products. The researcher and manager of Apex Nanotek, Chery Yang, introduced us to their main product, which is antimicrobial nanosilver activated carbon. Pure activated carbon, commonly used to treat sewage and industrial exhaust, is prone to bacterial growth. To overcome this problem, they integrate crystallized nanosilver into the activated carbon for their antimicrobial effects. One of their products is a showerhead, with nanosilver activated carbon filters to kill bacteria when water flows through the showerhead.
We tested the product by comparing SEM images between tap water and filtered water from the showerhead. The showerhead decreased the number of bacteria and larger particles from tap water! However, we also observed the release of nanoparticles from the filter, which will flow into wastewater. (Interviewed by Christine C., Kelly C., Yvonne W., Chansie Y., and Justin Y.)
Chery Yang (third person from the left), the main researcher of Apex Nanotek Corporation
Product of Apex Nanotek: Silver Spring Shower Head.
Figure 1-3 Tap water under SEM.
The image on the left shows a tap water sample under the SEM, in which we observed some bacteria (round objects that are approximately 1 μm in diameter). The SEM image on the left shows water that was filtered by the showerhead from Apex nanotek. There is less bacteria as the showerhead uses embedded nanosilver antibacterial filters. (SEM images: Christine C. and Florence L.)
THEPS Environmental Protection Engineering Company (中港環保工程股份有限公司)
We contacted the company that removes our nanoparticle waste because we wanted to know what happens when it leaves our lab. They directed us to National Cheng Kung university who actually treats the waste for them. The university uses chemicals and burning to aggregate nanoparticles. Through literature research, we discovered that burning nanoparticles is the most prevalent way for removal, however it is not 100% effective at removing all types of nanomaterials (Marr et. al. 2013). (Interviewed by Katherine H, Audrey T. and Christine C.)
Public Opinion
Survey Results
We created a survey that helped us identify public knowledge and misconceptions about synthetic biology and nanoparticle usage. Over 240 people completed the survey. (Survey created by Abby H., Christine C. and Emily C.)
Here are some results from our survey:
General Questions
- The majority of people think that gene modification is acceptable if the goal is to save or improve quality of life; however, it is not acceptable for non-medical related reasons, such as changing hair or eye color. In addition, most people do not have a preference between chemical or biological drug synthesis. These results suggest that people are accepting of genetic engineering when it is related to health and medicine.
- Environmentally, people are generally concerned with the wastewater that enters the ocean and the river. This gives weight to our project, because the quality of water is an important concern for the general public.
Two examples of general questions from our survey. (Left) 87% (201 out of 243 total responses) think that genes should be modified if the goal is to save or improve quality of life. (Right) 96.7% of the people surveyed care about the quality of wastewater (236 out of 244 total responses).Figure: Christine C.
Project-Specific Questions
- The majority of people have heard of nanoparticles and know that nanoparticles are used in consumer products; however, they do not know why nanoparticles are used.
- Most people believe that the government and nanoparticle manufacturers should share responsibility for the regulation of nanoparticle usage and disposal.
Two examples of project-specific questions from our survey. (Left) A majority of the people we asked (58.6%) do not know why nanoparticles are used in consumer products (143 out of 244 total responses). (Right) People believe that nanoparticle manufacturers and the government (including WWTPs) are most responsible for the regulation of nanoparticle usage and disposal. Figure: Christine C.
Bioethics Panel
We hosted a Bioethics Panel, where we invited students and teachers to discuss the moral, social and environmental concerns of our project. To encourage participants to consider the problems from multiple perspectives, we created a role-playing game and assigned different roles to participants. We then asked for their opinions on nanoparticle usage and disposal from the perspective of their assigned role. (Whole team activity)
For instance, one of our questions was:
“Dihua WWTP has no nanoparticle removal plan. Should this be the job of the wastewater plant? Or the nanoparticle manufacturer?”
The following roles were assigned:
- Wastewater plant manager
- Nanoparticle manufacturer
- Citizen
- Fisherman
- Fish
Most of the wastewater plant managers thought that nanoparticle manufacturers should be responsible for removing nanoparticles, because they have more information (e.g., solubility, toxicity, etc.) about their own products. However, many other participants were skeptical that manufacturers could be trusted to remove their own contamination and agreed that WWTPs should ultimately be responsible for cleaning water contaminated with nanoparticles.
This activity gave us great insight on how the public perceives nanoparticle usage and regulation in society. This also gave us a chance to talk to people about both the benefits and the dangers of using nanoparticles.