| NSF Org: |
CBET Division of Chemical, Bioengineering, Environmental, and Transport Systems |
| Recipient: |
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| Initial Amendment Date: | August 15, 2018 |
| Latest Amendment Date: | September 15, 2023 |
| Award Number: | 1804118 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Karl Rockne
krockne@nsf.gov (703)292-7293 CBET Division of Chemical, Bioengineering, Environmental, and Transport Systems ENG Directorate for Engineering |
| Start Date: | September 1, 2018 |
| End Date: | August 31, 2024 (Estimated) |
| Total Intended Award Amount: | $339,706.00 |
| Total Awarded Amount to Date: | $391,702.00 |
| Funds Obligated to Date: |
FY 2023 = $51,996.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
1608 4TH ST STE 201 BERKELEY CA US 94710-1749 (510)643-3891 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
Berkeley CA US 94720-1710 |
| 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, GOALI-Grnt Opp Acad Lia wIndus |
| Primary Program Source: |
01001819DB NSF RESEARCH & RELATED ACTIVIT |
| 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
Many cities face growing water scarcity. In response, these cities are developing innovative strategies to tap into alternative local sources of drinking water. One promising local source is treated wastewater that can be purified through advanced treatment processes. Like desalinated seawater, this purified water is also missing a natural community of bacteria that is present in all other drinking water sources. A lack of natural bacteria in purified water could provide an opportunity for unhealthy bacteria to grow. This study will compare the stability of bacteria in purified drinking water from seawater desalination to bacteria in water from traditional water sources. Additionally, the study will conduct laboratory tests to determine whether deliberately adding benign bacteria to purified wastewater can prevent instability of bacterial communities like those found in water infrastructure. The findings of this work will help engineers plan for the safe distribution of highly purified water to protect the public and help secure the Nation's water supply. The research will broaden participation in engineering by providing opportunities for research and career advancement for underrepresented students.
The advanced treatment of wastewater for direct potable reuse (DPR) generates extremely pure water. While the chemical conditioning of DPR water to prevent pipe corrosion is already under study, little work has investigated the potential impacts of DPR on the microbiology of drinking water distribution systems (DWDS). All DWDS harbor biofilms, and the addition of DPR water containing few cells may create biological instability and the potential for growth of opportunistic pathogens. Inoculating water with benign microorganisms via seeding may be effective for decreasing microbial risks in the DWDS. This study will examine whether deliberately seeding advanced treated water with a filter media-derived microbial community results in a more stable distribution system microbiome. The scientific objectives are to: 1) survey full-scale distribution systems in the U.S. to examine current biostability; 2) compare the microbial communities of two current systems, one conventional and one that uses RO-treated water, during distribution; 3) characterize changes to the microbial communities of mock-distribution systems during the introduction of blended conventional water and DPR water that is either microbially seeded or unseeded; and 4) examine the effect of disinfectant residual concentrations on the microbiome in seeded and unseeded mock-distribution systems. This study will use flow cytometry-based cell counting coupled to molecular methods, including amplicon and metagenomic sequencing, to observe microbiological changes in the full-scale and mock drinking water distribution systems. This study will provide insight into theoretical microbial ecology, the water microbiome, and produce valuable information to improve the design and operation of advanced treatment plants for direct potable reuse.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
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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.
The motivation for this research was advancing practices to provide safe drinking water in regions facing severe water scarcity. Specifically, we studied the emerging practice of direct potable reuse (DPR), in which highly purified municipal wastewater is used as a drinking water supply. The use of recycled water to meet urban water demand enables more water to be left in the environment where it can provide critical habitat in surface water ecosystems or replenish critically over-drafted groundwater aquifers. Compared to importing water from distant watersheds or desalinating seawater, DPR has the potential to provide water at lower cost and with a lower greenhouse gas footprint.
Our research aimed to address knowledge gaps about how advanced treatment affects the microbial community in the water, and how the microbial community will be altered when this purified water is introduced into an existing water distribution system. A combination of laboratory and field experiments were conducted, and a suite of advanced methods were used to characterize changes in microbial biomass (flow cytometry and ATP analysis) and the microbial community composition (16S amplicon sequencing and high-throughput metagenomics).
A commonly held view is that after advanced treatment, purified water is essentially sterile. We conducted field experiments at an advanced treatment facility to characterize the microbial water quality after reverse osmosis (RO), which is typically one of the last treatment steps. Using a novel filter approach we concentrated large volumes of RO permeate and sequenced the biomass. We observed a stable, consistent microbial community in the permeate that was not found in upstream samples, suggesting that the primary source was a biofilm growing on the permeate side of the membrane.
In laboratory experiments, we simulated what happens when this advanced treated water is fed to annular reactors, which simulate the drinking water pipes that distribute water to homes and businesses. As expected, we found that the reactors fed with advanced treated water contained lower microbial biomass than conventional tap water, due to its lower nutrient content. While the lower biomass is desirable, in previous research we have found that nutrients can be introduced during the storage and transport of the water, which then promotes microbial growth. Thus, we explored whether intentionally seeding this water with a microbial community via biological filtration could lead to a more stable microbial community downstream. Our results indicate that it is possible to “seed” advanced treated water with an engineered community from a Biological Activated Carbon filter, and that the seeded community persisted in the simulated distribution systems. Evidence suggested that both stochastic and deterministic factors contributed to the microbial community structure.
Overall, we conclude that seeding is a promising approach to prepare advanced treated water for distribution in full-scale DPR systems. However, while our benchtop experiments were helpful for isolating variables, they cannot capture the full complexity of real-world systems. Thus, we recommend that as the first full-scale DPR systems are implemented, the microbial water quality is characterized and monitored carefully before and after the introduction of the new water source utilizing the advanced new methods that were validated in this project.
This project provided significant training opportunities and development of human resources. From the researchers that were mentored as part of this project, two PhD students have started faculty positions, a postdoc started a career position at a National Laboratory, two undergraduates started PhD programs, one undergraduate started an MS program, and two undergraduates completed their degrees and are working as engineers.
Last Modified: 12/26/2024
Modified by: Kara L Nelson
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