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 the participants. We then asked for their opinions on NP 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

Apex Nanotek

To learn more about the applications of NPs, we visited a nanotech company that uses silver NPs 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 NPs 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

WWTP -- Dihua Wastewater Treatment Plant

In order to learn firsthand about the effect of NPs in WWTPs, we visited the Dihua WWTP (迪化污水處理廠). Here, we were given a tour around the plant, and were able to ask questions to the managers and people who work there. They confirmed that the current facilities are unable to remove NPs from wastewater mainly due to their small size. In addition to this information, they kindly provided us with samples of sludge, effluent water, and the polymers they add during the wastewater treatment process.

Throughout the year, we visited Dihua WWTP several times to discuss how our project could be implemented in their current system. We planned to add our proteorhodopsin (PR) bacteria in the aeration tanks, where other microbes already exist to break down organic solids. Our biofilm, attached to biocarriers, will then be placed in the sedimentation tanks (shown above). We gathered information about flow rates, tank dimensions, and water retention time in each tank to provide realistic conditions for our experimental, prototype, and modeling work. For example, during our conversation with WWTP engineers, we learned that wastewater is retained in aeration tanks and sedimentation tanks for up to 4.8 and 3.8 hours, respectively. This means PR and biofilm will only have up to ~5 hours and ~4 hours respectively, to interact and trap NPs in wastewater. Taking realistic timing into consideration, we added PR to citrate-capped silver NP (CC-AgNP) solution and mixed the solution for only up to ~5 hours (figure 2-6). We also added a flocculant powder (supplied by Dihua WWTP) to aggregate suspended solids, which mimics the next step in the treatment process.

Furthermore, we created calculators based on our mathematical models, which took variables--such as wastewater flow rate, bacteria concentration, and biofilm surface area--into consideration, to calculate the amount of PR bacteria or biofilm necessary to trap NPs. Lastly, we tested our PR bacteria and biofilm in realistic conditions by constructing a simulated WWTP (for example, see our biofilm trapping gold NPs in a simulated tank below!).

Boswell Wastewater Treatment Plant

Not all WWTPs are as large as the one in Taipei. One of our advisors (Jude Clapper) went to visit the Boswell WWTP in rural southwestern Pennsylvania. We learned that the same processes that occur in the Taipei Dihua WWTP also occur in the Boswell WWTP, but with different water flow rates and waste quantities. Since both facilities use a similar water purification process, we were inspired to create our current prototype design--a rotating polymeric bioreactor coated in biofilm--which is applicable to both WWTPs. This prototype will be placed in the secondary sedimentation tank, where the majority of organic solids have been removed and only smaller particles exist. The plant manager, Robert J. Blough, also confirmed that since our project is bacteria-based, it will be killed by UV light and chlorine in the disinfection tank, similar to the Dihua WWTP, before the water turns into effluent and goes to the rivers and oceans.

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 also has experience working with the EPA in Taiwan on wastewater treatments. We interviewed Mr. Brown about our methods to clean NPs in WWTPs 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.