| NSF Org: |
CBET Division of Chemical, Bioengineering, Environmental, and Transport Systems |
| Recipient: |
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| Initial Amendment Date: | July 19, 2017 |
| Latest Amendment Date: | July 19, 2017 |
| Award Number: | 1707069 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Mamadou Diallo
CBET Division of Chemical, Bioengineering, Environmental, and Transport Systems ENG Directorate for Engineering |
| Start Date: | August 1, 2017 |
| End Date: | July 31, 2021 (Estimated) |
| Total Intended Award Amount: | $304,892.00 |
| Total Awarded Amount to Date: | $304,892.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
2385 IRVING HILL RD LAWRENCE KS US 66045-7563 (785)864-3441 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
2385 Irving Hill Road Lawrence KS US 66045-7568 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | EnvE-Environmental Engineering |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.041 |
ABSTRACT
Proposal: 1707069
PI: Belinda Sturm
The focus of this project is the fate of microplastics (plastics < 5mm) in the liquid and biosolids discharged from water resource and recovery facilities (WRRFs). Microplastics are typically entrained within activated sludge and ultimately released to the environment through biosolids. The detrimental effects of plastics on marine vertebrates is well-documented and a major environmental concern. In this project the transport pathways for plastics will be identified. The results of this study will help reduce harmful marine ecosystem impacts. The PIs will engage municipalities through a full-scale sampling campaign and will disseminate the data in a web-based database that is publically accessible. They will continue to collaborate with high school teachers to refine teaching modules dealing with topics focused on microplastics and emerging contaminants.
Microplastics are likely to be removed when they are adsorbed or entrained within the activated sludge floc structure. The main hypothesis is that the sludge structure and extracellular polymeric substances (EPS) content are controlling variables to microplastic removal. In particular, the assumption is that microbial aggregates with high surface areas and high EPS content can capture more microplastics. To test this hypothesis the PIs will conduct a survey of select WRRFs with different primary and secondary treatment processes. To further quantify microplastics capture efficiencies, the PIs will determine the effect of EPS on microplastic adsorption and retention efficiency within lab-scale and pilot-scale reactors and compare conventional and aerobic granular sludge processes for microplastic adsorption. The activated sludge process, and particularly gravity sedimentation, was not designed to remove low density microplastic particles. Microplastics are likely to be removed when they are adsorbed or entrained within the activated sludge floc structure. As microplastic loads to WRRFs increase, it is important to study the effect of niche separation of microplastic-associated microorganisms on activated sludge process performance. One outcome of the research will be a better understanding the fate of microplastics in WRRFs. Results of this project will provide a framework for comprehensive management of microplastics contamination in WRRFs.
PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Microplastics (plastics <5 mm) are a growing global pollution problem. In urban environments, municipal wastewater acts as a catchment for microplastics, and discharge from resource and recovery facilities (WRRFs) may be a major source of microplastic contamination in water bodies. This project was jointly supported by the National Science Foundation and the Water Research Foundation to understand the fate of microplastics through wastewater treatment plants. The research provides data for microplastic releases from municipal wastewater discharge and biosolids application. Data was collected from eight full-scale treatment plants across the United States. At each facility, duplicate or triplicate fluid samples were filtered at multiple stages of treatment: raw influent, primary clarifier effluent, secondary clarifier effluent, tertiary treatment effluent (i.e., after membrane filtration), effluent at the point of discharge. In addition, a control sample was filtered at each site after sample filtration. Each sample that was filtered passed through three stainless steel mesh sizes (25 um, 100 um, and 300 um). Biosolids samples after dewatering were collected from four facilities. In total, this represented 62 samples, from which microplastics were extracted from three stainless steel filters for each sample (186 samples in total), quantified, and characterized. In addition to the national survey, laboratory wastewater reactors were operated to understand the role of extracellular polymeric substances in capturing microplastics within the activated sludge floc or granule structure. Finally, a field experiment was performed with biosolids application at agronomic rates, and the fate of microplastics in runoff and soil infiltration was observed.
The Intellectual Merit of this proposal is framing a comprehensive strategy for microplastic management from WRRFs. Influent wastewater had an average of 155 ± 178 MPs/L, with 76% of these particles at a size between 25 and 100 um. Primary clarifiers removed 70% of the microplastics. Only 4% of the microplastics in the influent were discharged in the effluent. Biosolids contain four to five times the microplastics concentration than effluent. The mass majority of microplastics are entrained within activated sludge and ultimately released to the environment through biosolids.
Laboratory wastewater reactors were operated to understand fundamental mechanisms that may influence microplastic absorption or entrapment within activated sludge flocs. It was hypothesized that biofilm or fixed film systems with high extracellular polymeric substance (EPS) content will capture more microplastic. Microplastics were removed more efficiently (93 to 95% removal) in reactors with higher loosely-bound EPS and smaller particles sizes than reactors with larger particles and less EPS (66 to 74% removal). Microplastics were also observed under the microscope in the outer layers of particles entrapped in EPS.
Lastly, the environmental fate of microplastics land applied as biosolids was tested in field plot studies at the KU Environmental Field Station. Biosolids were collected from the Kansas River Wastewater Treatment Plant and applied evenly to six test plots at the agronomic application rate for corn. Over the 1-month study period, microplastics were transported to runoff in five simulated rain events and were observed to infiltrate into deeper soil layers. The method of biosolids application (incorporation versus surface spreading) affected the transport of microplastics in the environment.
The Broader Impacts of this proposal center around creating microplastic awareness among wastewater professionals and regulators. Sixteen professional presentations were made to wastewater professionals and environmental regulators during this project. Specifically, results were presented through several webinars during the COVID-19 pandemic, with over 1000 attendees for the Water Research Foundation webinar. The results were also presented within Knowledge Development Forums at the Water Environment Federation’s annual conference each year of the project.
Last Modified: 04/23/2022
Modified by: Belinda Sturm
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