Grantee Research Project Results
2023 Progress Report: Removal of Microplastics from a Domestic Wastewater Treatment Plant
EPA Grant Number: SU840406Title: Removal of Microplastics from a Domestic Wastewater Treatment Plant
Investigators: Han, Bangshuai , Gruver, Josh , Venturelli, Paul , Yacoub, Moayad , Adjornor, Bless , Mohanta, Tusher , Briddell, Nadia , Ogle, Sarah , Routt, Lillian
Institution: Ball State University
EPA Project Officer: Harper, Jacquelyn
Phase: I
Project Period: July 1, 2022 through June 30, 2023 (Extended to June 30, 2024)
Project Period Covered by this Report: July 1, 2022 through June 30,2023
Project Amount: $25,000
RFA: 18th Annual P3 Awards: A National Student Design Competition Focusing on People, Prosperity and the Planet (2021) RFA Text | Recipients Lists
Research Category: P3 Awards , P3 Challenge Area - Safe and Sustainable Water Resources
Objective:
The overall research goal of this project is to address the need for a better understanding of the presence and removal of microplastics in wastewater treatment processes. This involves improving current sampling and testing procedures and considering the temporal and seasonal variation of microplastics pollution. The specific objectives included (1) improving and streamlining current microplastics sampling and testing procedures in wastewater; (2) identifying the quantities and types of microplastics present at each major treatment stage in the Muncie Wastewater Treatment Plant (WWTP); (3) revealing temporal and seasonal variations of the abundance of microplastics entering the studied WWTP; (4) connecting the temporal pattern observed in microplastics with local water use patterns and seasonal climate; and (5) analyzing relationships between removal efficiency, flow rate, season, and stages of treatment. Microplastic pollution is a pervasive issue within marine and freshwater environments and has recently emerged as a major contamination concern. The bioaccumulation and biomagnification of microplastics within the food web could result in adverse physical and chemical impacts on both the ecosystem and the human body. Domestic WWTPs are major hubs that receive and remove pollutants. Despite being largely removed during treatment processes, wastewater effluent remains a major pathway for microplastics to enter the environment due to the high-water discharge rate from WWTPs. However, the removal efficiency and processes of WWTPs regarding microplastic contamination are not well understood, partly due to the lack of streamlined and standardized methods for sampling and testing microplastics in wastewater. The current established sampling and testing methods usually take 3-7 days to complete a single sample, with limitations of potential sample contaminations, loss of microplastic particles, and inaccuracies. Consequently, most studies are conducted within a limited time frame by taking grab samples over a few days and/or at a few sites. Therefore, this research aimed to tackle the research gaps related to the lack of standard methods, and the data gaps concerning microplastics in wastewater, through the research objectives listed above. This research aligns well with the P3 approach because it offers solutions for protecting the environment, provides science data to support future innovations in WWTPs, presents cutting-edge research results for the EPA to consider in policy-makings regarding microplastic pollution, and benefits community health. Phase I of the project has directly involved four graduate students and three undergraduate students, and indirectly impacted over 60 undergraduate students through classroom instructions. The research outcomes have been shared with local community partners including the Bureau of Water Quality (BWQ), the Muncie WWTP, and other interested local parties such as the Delaware County Soil and Water Conservation District, and been disseminated via local, regional, and international conference presentations, as well as a peer-reviewed article. |
Progress Summary:
The Phase I research collected bi-weekly grab samples with duplicates from the Muncie WWTP spanning from February to May 2021. The samples were then filtered using an assembled stack of sieves with mesh sizes between 425 and 25 μm. They were then digested using Fenton Reagent as a method of organic oxidation and subjected to density separation via a centrifuge to isolate microplastics. Then microplastics were visually identified under an optical microscope based on their morphology. Synthetic fibers were identified as the predominant plastic morphological type across all size ranges, accounting for 64.67% of the total plastic pieces collected at each sampling location. Following this, fragments and films constituted 35.07%, while foams made up only 0.23% of microplastic particles sampled (Figure 1 A). Throughout the sampling period, there was a general increasing trend in microplastic concentration, observed from late February to mid-May. Correlation analysis indicated that the concentration of microplastics did not exhibit a strong relationship with either river discharge or plant inflow (Figure 1 B).
Due to the explorative nature of the testing procedures for this new contaminant, we have also streamlined and simplified the workflow to enhance testing efficiency and minimize errors (Figure 2). Through the research conducted in Phase I, this newly developed testing methodology will benefit other WWTPs and researchers in the microplastics field. In comparison to the variations in testing processes observed among researchers, this new methodology is considerably more streamlined, less time consuming, and less confusing. For instance, we used a combination of onsite sieving and in-lab filtration, which eliminates the burden of unnecessary sample transport when samples can be sieved directly on site. The conventional method for organic matter removal relies on oxidation using hydrogen peroxide (H2O2). This step alone requires 3–7 days to yield satisfactory results. However, by adopting the Fenton reagent, a combination of iron catalysts and, for organic matter oxidation, it takes less than 1 hour to effectively digest organic matter. We also tested the impact of digestion on microplastics and determined that the particles were not morphologically impacted using Fenton reagent and at drying temperature of 90 o C within half an hour. No deformation or deterioration in shape was noticed (Figure 1 C). This step significantly reduces the processing time and eliminates the need for extended waiting periods.
Density separation is another crucial step in microplastic detection, involving leaving the samples overnight in a high-concentration salt solution, or using a centrifuge to expedite the process. A variety of salts were suggested in literature to increase solution density for better separation of microplastics. Our team adopted the method that employed a centrifuge with addition of ZnCl2 and were able to achieve satisfactory separation in just 20 minutes.
Furthermore, we analyzed the sample transfer steps and identified opportunities for improvement. For example, we repositioned the step of the application of Rose Bengal dye – a process intended to dye non-plastic materials to help visually identify microplastics - from after density separation to before that step. Overall, the times of sample transfer were reduced from typically four to six times to three times. Although this adjustment may appear minor, it has a noteworthy impact as it significantly shortened the time for consequent oven-drying after each transfer. This adjustment allows a more rapid analytical process and helped prevent potential errors and contaminants introduced with unnecessary transfer and drying. We have also made preliminary tests of the dosage and running time for organic degradation to ensure that our procedures were both effective and resource efficient. With the streamlined processes, the analysis time for every sample was significantly reduced from the original three to seven days to about two days. Findings from this research are helpful for the WWTP to evaluate future renovations related to the removal of microplastics as well as contribute to cutting-edge knowledge in the field.
Figure 1.. Preliminary results from Phase I. Panel A shows the relative abundance of fragments and films, fibers and foams found in samples. Panel B shows the temporal changes, along with discharge in the river and inflow rate into the WWRP. Panel C illustrates an example of test on the possible impact of digestion on plastic particle shape. Polypropylene was uses in this example, we also tested other commonly used plastics such as polyethylene, polystyrene and polyyethylene terephthalate particles
Moreover, by engaging undergraduate and graduate students, the research trained the next generation of scientists and raised awareness of microplastic pollution at an early stage in their careers. The research also provided opportunities for students to gain hands-on educational experiences that melded organically with classroom activities. In addition to directly involving students in the research project, research findings from the project have been integrated into the PI’s water classes. These activities advanced BSU’s goals to increase student learning and strengthen students’ competitive entry into the job market.
The PI has also engaged with local stakeholders and public agencies, including the BWQ and the Muncie WWTP, to study water quality and quantity and timing regime issues in local water bodies. The research facilitated improved engagement with other stakeholders, including the EPA, that have interests in the sustainability of water resources under human interruptions. This also aligns with another of BSU’s strategic goals to support community engagement.
Figure 2. Streamlined laboratory analytical procedures for microplastics collected from wastewater
Future Activities:
This Phase I project has gathered data that serve as a starting point to analyze the quantities and types of microplastics present in wastewater in the influent and at each treatment stage and revealed temporal and seasonal variations of the abundance of microplastics entering the Muncie WWTP. The research also streamlined microplastics sampling and testing procedures in wastewater. The findings have been disseminated at local, regional, and international conferences. Moreover, a peer-reviewed publication has also been produced with the support of this grant. The project will be expanded pending future support for a Phase II grant to collect longer-term samples to better reveal the relationships between removal efficiency, flow rate, season, lifestyle, and stages of treatment, and further improve the testing methodology.
Journal Articles:
No journal articles submitted with this report: View all 4 publications for this projectSupplemental Keywords:
microplastics, organic matter, wastewater, detectionRelevant Websites:
Occurrence and Source of Microplastics in the Sagarmatha National Park, Nepal Exit
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.