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Hozalski RM, Zhao X, Kim T, LaPara TM. On-site filtration of large sample volumes improves the detection of opportunistic pathogens in drinking water distribution systems. Appl Environ Microbiol 2024; 90:e0165823. [PMID: 38236032 PMCID: PMC10880612 DOI: 10.1128/aem.01658-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 12/06/2023] [Indexed: 01/19/2024] Open
Abstract
In this study, we compared conventional vacuum filtration of small volumes through disc membranes (effective sample volumes for potable water: 0.3-1.0 L) with filtration of high volumes using ultrafiltration (UF) modules (effective sample volumes for potable water: 10.6-84.5 L) for collecting bacterial biomass from raw, finished, and tap water at seven drinking water systems. Total bacteria, Legionella spp., Legionella pneumophila, Mycobacterium spp., and Mycobacterium avium complex in these samples were enumerated using both conventional quantitative PCR (qPCR) and viability qPCR (using propidium monoazide). In addition, PCR-amplified gene fragments were sequenced for microbial community analysis. The frequency of detection (FOD) of Legionella spp. in finished and tap water samples was much greater using UF modules (83% and 77%, respectively) than disc filters (24% and 33%, respectively). The FODs for Mycobacterium spp. in raw, finished, and tap water samples were also consistently greater using UF modules than disc filters. Furthermore, the number of observed operational taxonomic units and diversity index values for finished and tap water samples were often substantially greater when using UF modules as compared to disc filters. Conventional and viability qPCR yielded similar results, suggesting that membrane-compromised cells represented a minor fraction of total bacterial biomass. In conclusion, our research demonstrates that large-volume filtration using UF modules improved the detection of opportunistic pathogens at the low concentrations typically found in public drinking water systems and that the majority of bacteria in these systems appear to be viable in spite of disinfection with free chlorine and/or chloramine.IMPORTANCEOpportunistic pathogens, such as Legionella pneumophila, are a growing public health concern. In this study, we compared sample collection and enumeration methods on raw, finished, and tap water at seven water systems throughout the State of Minnesota, USA. The results showed that on-site filtration of large water volumes (i.e., 500-1,000 L) using ultrafiltration membrane modules improved the frequency of detection of relatively rare organisms, including opportunistic pathogens, compared to the common approach of filtering about 1 L using disc membranes. Furthermore, results from viability quantitative PCR (qPCR) with propidium monoazide were similar to conventional qPCR, suggesting that membrane-compromised cells represent an insignificant fraction of microorganisms. Results from these ultrafiltration membrane modules should lead to a better understanding of the microbial ecology of drinking water distribution systems and their potential to inoculate premise plumbing systems with opportunistic pathogens where conditions are more favorable for their growth.
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Affiliation(s)
- Raymond M. Hozalski
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota Twin Cities, Minneapolis, Minnesota, USA
- Biotechnology Institute, University of Minnesota Twin Cities, St. Paul, Minnesota, USA
| | - Xiaotian Zhao
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota Twin Cities, Minneapolis, Minnesota, USA
| | - Taegyu Kim
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota Twin Cities, Minneapolis, Minnesota, USA
| | - Timothy M. LaPara
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota Twin Cities, Minneapolis, Minnesota, USA
- Biotechnology Institute, University of Minnesota Twin Cities, St. Paul, Minnesota, USA
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Kim T, Zhao X, LaPara TM, Hozalski RM. Flushing Temporarily Improves Microbiological Water Quality for Buildings Supplied with Chloraminated Surface Water but Has Little Effect for Groundwater Supplies. Environ Sci Technol 2023; 57:5453-5463. [PMID: 36952669 DOI: 10.1021/acs.est.2c08123] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Microbial communities in premise plumbing systems were investigated after more than 2 months of long-term stagnation, during a subsequent flushing event, and during post-flush stagnation. Water samples were collected from showers in buildings supplied with chlorinated groundwater, untreated groundwater, and chloraminated surface water. The building supplied with chlorinated groundwater generally had the lowest bacterial concentrations across all sites (ranging from below quantification limit to 5.2 log copies/L). For buildings supplied with untreated groundwater, bacterial concentrations (5.0 to 7.6 log copies/L) and microbial community diversity index (ACE) values were consistent throughout sampling. Nontuberculous mycobacteria (NTM) and Legionella pneumophila were not detected in any groundwater-supplied buildings. Total bacteria, Legionella spp., and NTM were abundant in the surface water-supplied buildings following long-term stagnation (up to 7.6, 6.2, and 7.6 log copies/L, respectively). Flushing decreased these concentrations by ∼1 to >4 log units and reduced microbial community diversity, but the communities largely recovered within a week of post-flush stagnation. The results suggest that buildings supplied with disinfected surface water are more likely than buildings supplied with treated or untreated groundwater to experience deleterious changes in microbiological water quality during stagnation and that the water quality improvements from flushing with chloraminated water, while substantial, are short-lived.
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Affiliation(s)
- Taegyu Kim
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota Twin Cities, 500 Pillsbury Drive S.E., Minneapolis, Minnesota 55455, United States
| | - Xiaotian Zhao
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota Twin Cities, 500 Pillsbury Drive S.E., Minneapolis, Minnesota 55455, United States
| | - Timothy M LaPara
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota Twin Cities, 500 Pillsbury Drive S.E., Minneapolis, Minnesota 55455, United States
- Biotechnology Institute, University of Minnesota Twin Cities, 1479 Gortner Avenue, St. Paul, Minnesota 55108, United States
| | - Raymond M Hozalski
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota Twin Cities, 500 Pillsbury Drive S.E., Minneapolis, Minnesota 55455, United States
- Biotechnology Institute, University of Minnesota Twin Cities, 1479 Gortner Avenue, St. Paul, Minnesota 55108, United States
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Ma B, LaPara TM, Kim T, Hozalski RM. Multi-scale Investigation of Ammonia-Oxidizing Microorganisms in Biofilters Used for Drinking Water Treatment. Environ Sci Technol 2023; 57:3833-3842. [PMID: 36811531 DOI: 10.1021/acs.est.2c06858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Ammonia-oxidizing microorganisms (AOMs) include ammonia-oxidizing bacteria (AOB), archaea (AOA), and Nitrospira spp. sublineage II capable of complete ammonia oxidation (comammox). These organisms can affect water quality not only by oxidizing ammonia to nitrite (or nitrate) but also by cometabolically degrading trace organic contaminants. In this study, the abundance and composition of AOM communities were investigated in full-scale biofilters at 14 facilities across North America and in pilot-scale biofilters operated for 18 months at a full-scale water treatment plant. In general, the relative abundance of AOM in most full-scale biofilters and in the pilot-scale biofilters was as follows: AOB > comammox Nitrospira > AOA. The abundance of AOB in the pilot-scale biofilters increased with increasing influent ammonia concentration and decreasing temperature, whereas AOA and comammox Nitrospira exhibited no correlations with these parameters. The biofilters affected AOM abundance in the water passing through the filters via collecting and shedding but exhibited a minor influence on the composition of AOB and Nitrospira sublineage II communities in the filtrate. Overall, this study highlights the relative importance of AOB and comammox Nitrospira compared to AOA in biofilters and the influence of filter influent water quality on AOM in biofilters and their release into the filtrate.
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Affiliation(s)
- Ben Ma
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, Minnesota 55455, United States
| | - Timothy M LaPara
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, Minnesota 55455, United States
- Biotechnology Institute, University of Minnesota, 1479 Gortner Avenue, Saint Paul, Minnesota 55108, United States
| | - Taegyu Kim
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, Minnesota 55455, United States
| | - Raymond M Hozalski
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, Minnesota 55455, United States
- Biotechnology Institute, University of Minnesota, 1479 Gortner Avenue, Saint Paul, Minnesota 55108, United States
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Bueno I, Beaudoin A, Arnold WA, Kim T, Frankson LE, LaPara TM, Kanankege K, Wammer KH, Singer RS. Quantifying and predicting antimicrobials and antimicrobial resistance genes in waterbodies through a holistic approach: a study in Minnesota, United States. Sci Rep 2021; 11:18747. [PMID: 34548591 PMCID: PMC8455696 DOI: 10.1038/s41598-021-98300-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Accepted: 09/03/2021] [Indexed: 11/25/2022] Open
Abstract
The environment plays a key role in the spread and persistence of antimicrobial resistance (AMR). Antimicrobials and antimicrobial resistance genes (ARG) are released into the environment from sources such as wastewater treatment plants, and animal farms. This study describes an approach guided by spatial mapping to quantify and predict antimicrobials and ARG in Minnesota’s waterbodies in water and sediment at two spatial scales: macro, throughout the state, and micro, in specific waterbodies. At the macroscale, the highest concentrations across all antimicrobial classes were found near populated areas. Kernel interpolation provided an approximation of antimicrobial concentrations and ARG abundance at unsampled locations. However, there was high uncertainty in these predictions, due in part to low study power and large distances between sites. At the microscale, wastewater treatment plants had an effect on ARG abundance (sul1 and sul2 in water; blaSHV, intl1, mexB, and sul2 in sediment), but not on antimicrobial concentrations. Results from sediment reflected a long-term history, while water reflected a more transient record of antimicrobials and ARG. This study highlights the value of using spatial analyses, different spatial scales, and sampling matrices, to design an environmental monitoring approach to advance our understanding of AMR persistence and dissemination.
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Affiliation(s)
- Irene Bueno
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, 1971 Commonwealth Ave., St. Paul, MN, 55108, USA.
| | - Amanda Beaudoin
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, 1971 Commonwealth Ave., St. Paul, MN, 55108, USA.,Minnesota Department of Health, P.O. Box 64975, St. Paul, MN, 55164-0975, USA
| | - William A Arnold
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, MN, 55455, USA.,Water Resources Science Program, University of Minnesota, 1985 Buford Ave., St. Paul, MN, 55108, USA
| | - Taegyu Kim
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, MN, 55455, USA
| | - Lara E Frankson
- Water Resources Science Program, University of Minnesota, 1985 Buford Ave., St. Paul, MN, 55108, USA
| | - Timothy M LaPara
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, MN, 55455, USA
| | - Kaushi Kanankege
- Center for Animal Health and Food Safety, College of Veterinary Medicine, University of Minnesota, 1354 Eckles Ave., St. Paul, MN, 55108, USA
| | - Kristine H Wammer
- College of Arts & Sciences, University of St. Thomas, 2115 Summit Ave., St. Paul, MN, 55105, USA
| | - Randall S Singer
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, 1971 Commonwealth Ave., St. Paul, MN, 55108, USA
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Kim T, Hite M, Rogacki L, Sealock AW, Sprouse G, Novak PJ, LaPara TM. Dissolved oxygen concentrations affect the function but not the relative abundance of nitrifying bacterial populations in full-scale municipal wastewater treatment bioreactors during cold weather. Sci Total Environ 2021; 781:146719. [PMID: 33812097 DOI: 10.1016/j.scitotenv.2021.146719] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Revised: 03/19/2021] [Accepted: 03/20/2021] [Indexed: 06/12/2023]
Abstract
This study aimed to understand the effect of different dissolved oxygen (DO) concentrations on the abundance and performance of nitrifying bacteria in full-scale wastewater treatment bioreactors, particularly during the winter when nitrifying bacterial activity is often negligible. Biomass samples were collected from three parallel full-scale bioreactors with low DO concentrations (<1.3 mg/ L) and from two full-scale bioreactors with higher DO concentrations (~4.0 and ~2.3 mg/ L). The relative abundance of nitrifying bacteria was determined by sequencing of PCR-amplified 16S rRNA gene fragments. In the three bioreactors with low DO concentrations, effluent ammonia concentrations sharply increased with a decline in temperature below approximately 17 °C, while the bioreactors with high DO concentrations showed stable nitrification regardless of temperature. Even with the decline in nitrification during the winter in the three low DO bioreactors, the relative abundance of ammonia oxidizing bacteria (mostly Nitrosomonas spp.) was curiously maintained. The relative abundance of nitrite oxidizing bacteria was similarly maintained, although there were substantial seasonal fluctuations in the relative abundance values of Nitrospira spp. versus Nitrotoga spp. This research suggests that nitrification activity can be controlled during the winter via DO to produce better effluent quality with high DO concentrations or to reduce aeration costs with a concomitant decline in nitrification activity.
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Affiliation(s)
- Taegyu Kim
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota Twin-Cities, 500 Pillsbury Drive S.E., Minneapolis, MN, USA
| | - Molly Hite
- Water Resources Science Graduate Program, University of Minnesota Twin-Cities, 173 McNeal Hall, 1985 Buford Ave., St. Paul, MN, USA
| | - Larry Rogacki
- Metropolitan Council Environmental Services, 2400 Childs Road, St. Paul, MN, USA
| | - Adam W Sealock
- Metropolitan Council Environmental Services, 2400 Childs Road, St. Paul, MN, USA
| | - George Sprouse
- Metropolitan Council Environmental Services, 2400 Childs Road, St. Paul, MN, USA
| | - Paige J Novak
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota Twin-Cities, 500 Pillsbury Drive S.E., Minneapolis, MN, USA; Water Resources Science Graduate Program, University of Minnesota Twin-Cities, 173 McNeal Hall, 1985 Buford Ave., St. Paul, MN, USA; Biotechnology Institute, University of Minnesota Twin Cities, 1479 Gortner Ave, St. Paul, MN, USA
| | - Timothy M LaPara
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota Twin-Cities, 500 Pillsbury Drive S.E., Minneapolis, MN, USA; Water Resources Science Graduate Program, University of Minnesota Twin-Cities, 173 McNeal Hall, 1985 Buford Ave., St. Paul, MN, USA; Biotechnology Institute, University of Minnesota Twin Cities, 1479 Gortner Ave, St. Paul, MN, USA.
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6
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McGivern BB, McDonell RK, Morris SK, LaPara TM, Donato JJ. Novel class 1 integron harboring antibiotic resistance genes in wastewater-derived bacteria as revealed by functional metagenomics. Plasmid 2021; 114:102563. [PMID: 33515651 DOI: 10.1016/j.plasmid.2021.102563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 01/19/2021] [Accepted: 01/23/2021] [Indexed: 11/15/2022]
Abstract
Combatting antibiotic resistance is critical to our ability to treat infectious diseases. Here, we identified and characterized diverse antimicrobial resistance genes, including potentially mobile elements, from synthetic wastewater treatment microcosms exposed to the antibacterial agent triclosan. After seven weeks of exposure, the microcosms were subjected to functional metagenomic selection across 13 antimicrobials. This was achieved by cloning the combined genetic material from the microcosms, introducing this genetic library into E. coli, and selecting for clones that grew on media supplemented with one of the 13 antimicrobials. We recovered resistant clones capable of growth on media supplemented with a single antimicrobial, yielding 13 clones conferring resistance to at least one antimicrobial agent. Antibiotic susceptibility analysis revealed resistance ranging from 4 to >50 fold more resistant, while one clone showed resistance to multiple antibiotics. Using both Sanger and SMRT sequencing, we identified the predicted active gene(s) on each clone. One clone that conferred resistance to tetracycline contained a gene encoding a novel tetA-type efflux pump that was named TetA(62). Three clones contained predicted active genes on class 1 integrons. One integron had a previously unreported genetic arrangement and was named In1875. This study demonstrated the diversity and potential for spread of resistance genes present in human-impacted environments.
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Affiliation(s)
- Bridget B McGivern
- Chemistry Department, University of St. Thomas, St. Paul, MN 55105, United States of America
| | - Rylie K McDonell
- Chemistry Department, University of St. Thomas, St. Paul, MN 55105, United States of America
| | - Sydney K Morris
- Chemistry Department, University of St. Thomas, St. Paul, MN 55105, United States of America
| | - Timothy M LaPara
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, Minneapolis, MN 55455, United States of America
| | - Justin J Donato
- Chemistry Department, University of St. Thomas, St. Paul, MN 55105, United States of America.
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Hozalski RM, LaPara TM, Zhao X, Kim T, Waak MB, Burch T, McCarty M. Flushing of Stagnant Premise Water Systems after the COVID-19 Shutdown Can Reduce Infection Risk by Legionella and Mycobacterium spp. Environ Sci Technol 2020; 54:15914-15924. [PMID: 33232602 DOI: 10.1021/acs.est.0c06357] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
There is concern about potential exposure to opportunistic pathogens when reopening buildings closed due to the COVID-19 pandemic. In this study, water samples were collected before, during, and after flushing showers in five unoccupied (i.e., for ∼2 months) university buildings with quantification of opportunists via a cultivation-based assay (Legionella pneumophila only) and quantitative PCR. L. pneumophila were not detected by either method; Legionella spp., nontuberculous mycobacteria (NTM), and Mycobacterium avium complex (MAC), however, were widespread. Using quantitative microbial risk assessment (QMRA), the estimated risks of illness from exposure to L. pneumophila and MAC via showering were generally low (i.e., less than a 10-7 daily risk threshold), with the exception of systemic infection risk from MAC exposure in some buildings. Flushing rapidly restored the total chlorine (as chloramine) residual and decreased bacterial gene targets to building inlet concentrations within 30 min. During the postflush stagnation period, the residual chlorine dissipated within a few days and bacteria rebounded, approaching preflush concentrations after 6-7 days. These results suggest that flushing can quickly improve water quality in unoccupied buildings, but the improvement may only last a few days.
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Affiliation(s)
- Raymond M Hozalski
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, Minneapolis 55455, Minnesota, United States
| | - Timothy M LaPara
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, Minneapolis 55455, Minnesota, United States
| | - Xiaotian Zhao
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, Minneapolis 55455, Minnesota, United States
| | - Taegyu Kim
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, Minneapolis 55455, Minnesota, United States
| | - Michael B Waak
- Norwegian University of Science and Technology, Trondheim 7031, Norway
- Department of Infrastructure, SINTEF Community, Trondheim 7031, Norway
| | - Tucker Burch
- Agricultural Research Service, U.S. Department of Agriculture, Marshfield, Wisconsin 54449, United States
| | - Michael McCarty
- School of Public Health, University of Minnesota, Minneapolis 55455, Minnesota, United States
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Ma B, LaPara TM, Hozalski RM. Microbiome of Drinking Water Biofilters is Influenced by Environmental Factors and Engineering Decisions but has Little Influence on the Microbiome of the Filtrate. Environ Sci Technol 2020; 54:11526-11535. [PMID: 32786579 DOI: 10.1021/acs.est.0c01730] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Bacterial communities in biofilters can improve drinking water quality through the biodegradation of dissolved contaminants but also pose potential risks by harboring and shedding microbes into the drinking water distribution system. In this study, pilot-scale granular activated carbon (GAC)-sand and anthracite-sand pilot-scale biofilters were investigated to determine the effects of filter design and operation on the microbiome of the filter media and its relationship to the microbiome in the filter effluent water. Bacterial abundance in the biofilters was relatively stable over time. Bacterial community composition exhibited spatial variation (i.e., with bed depth) and temporal variation linked to water quality changes. Bacterial community composition was significantly affected by the media type (GAC vs anthracite) and backwashing strategy (chloraminated water vs nonchloraminated water). The biofilters reduced bacterial abundance in the water (∼70%) but had only a minor effect on the bacterial community composition in the filtrate. Overall, our results suggest that the bacterial communities growing on biofilters affect filtered water quality primarily through the biotransformation of pollutants and nutrients rather than by altering the microbial community composition of the water as it passes through the filter.
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Affiliation(s)
- Ben Ma
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, Minnesota 55455, United States
| | - Timothy M LaPara
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, Minnesota 55455, United States
- Biotechnology Institute, University of Minnesota, 1479 Gortner Avenue, Saint Paul, Minnesota 55108, United States
| | - Raymond M Hozalski
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, Minnesota 55455, United States
- Biotechnology Institute, University of Minnesota, 1479 Gortner Avenue, Saint Paul, Minnesota 55108, United States
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Ma B, LaPara TM, N Evans A, Hozalski RM. Effects of geographic location and water quality on bacterial communities in full-scale biofilters across North America. FEMS Microbiol Ecol 2020; 96:5698304. [PMID: 31913449 DOI: 10.1093/femsec/fiz210] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Accepted: 01/07/2020] [Indexed: 11/14/2022] Open
Abstract
Spatial patterns of bacterial community composition often follow a distance-decay relationship in which community dissimilarity increases with geographic distance. Such a relationship has been commonly observed in natural environments, but less so in engineered environments. In this study, bacterial abundance and community composition in filter media samples (n = 57) from full-scale rapid biofilters at 14 water treatment facilities across North America were determined using quantitative polymerase chain reaction and Illumina HiSeq high-throughput sequencing targeting the 16S rRNA gene, respectively. Bacteria were abundant on the filter media (108.8±0.3 to 1010.7±0.2 16S rRNA gene copies/cm3 bed volume) and the bacterial communities were highly diverse (Shannon index: 5.3 ± 0.1 to 8.4 ± 0.0). Significant inter-filter variations in bacterial community composition were observed, with weighted UniFrac dissimilarity values following a weak but highly significant distance-decay relationship (z = 0.0057 ± 0.0006; P = 1.8 × 10-22). Approximately 50% of the variance in bacterial community composition was explained by the water quality parameters measured at the time of media sample collection (i.e. pH, temperature and dissolved organic carbon concentration). Overall, this study suggested that the microbiomes of biofilters are primarily shaped by geographic location and local water quality conditions but the influence of these factors on the microbiomes is tempered by filter design and operating conditions.
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Affiliation(s)
- Ben Ma
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, MN 55455, United States
| | - Timothy M LaPara
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, MN 55455, United States
- Biotechnology Institute, University of Minnesota, 1479 Gortner Ave, Saint Paul, MN 55108 , United States
| | - Ashley N Evans
- Arcadis U.S. Inc., 1717 W. 6th St. Suite 210, Austin, TX, 78703, United States
| | - Raymond M Hozalski
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, MN 55455, United States
- Biotechnology Institute, University of Minnesota, 1479 Gortner Ave, Saint Paul, MN 55108 , United States
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10
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Gordon BA, Lenhart C, LaPara TM. A comparison of nitrate removal and denitrifying bacteria populations among three wetland plant communities. J Environ Qual 2020; 49:210-219. [PMID: 33016351 DOI: 10.1002/jeq2.20004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 08/18/2019] [Accepted: 10/21/2019] [Indexed: 06/11/2023]
Abstract
Reed canary grass (Phalaris arundinacea L.) is an invasive, cool-season grass commonly dominating wetlands with high nutrient loads. Its impact on nitrogen removal via denitrification in wetlands is unknown. Most studies of denitrification in treatment wetlands have focused on the effects of physical or chemical variables and not on the effects of plant roots on the soil environment. The purpose of this study was to measure effects of plant type on denitrification rates in typical wetland soils of the midwestern United States by comparing wet prairie mix, switchgrass-dominated, and reed canary grass plant communities. Nitrate (NO3 - ) removal and other parameters were measured in miniature wetlands, or mesocosms, containing each plant community transplanted from a small agricultural treatment wetland in southern Minnesota. Quantitative polymerase chain reaction analysis was used to quantify the total bacteria population (measured with 16S rRNA genes) and denitrifying gene abundance (measured with nosZ genes) from the rhizosphere of each plant community. The wet prairie mix mesocosms on average removed the most NO3 - in each test (p = .01 and .08). Whereas the wet prairie mix removed the most NO3 - from the surface water (p < .01), reed canary grass removed more from the subsurface (p < .01). Ratios of denitrifying to total bacteria were higher in the wet prairie mix than in the other communities' root zones (p < .05). Results suggest that reed canary grass invasion could reduce denitrification in wetlands, especially during the spring and fall when it is growing but other plants are dormant.
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Affiliation(s)
- Brad A Gordon
- Water Resources Science Graduate Program, University of Minnesota, St. Paul, MN, 55108
| | - Christian Lenhart
- Ecological Engineering Group, Department of Bioproducts and Biosystems Engineering, University of Minnesota, 303 BAE Hall, 1390 Eckles Ave., St. Paul, MN, 55108
| | - Timothy M LaPara
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, MN, 55455
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Waak MB, LaPara TM, Hallé C, Hozalski RM. Nontuberculous Mycobacteria in Two Drinking Water Distribution Systems and the Role of Residual Disinfection. Environ Sci Technol 2019; 53:8563-8573. [PMID: 31287948 DOI: 10.1021/acs.est.9b01945] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Nontuberculous mycobacteria (NTM) are frequently found in chloraminated drinking water distribution systems (DWDSs) due to their chloramine tolerance. NTM were investigated in the water-main biofilms and drinking water of a chloraminated DWDS in the United States (initial chloramine residual = 3.8 ± 0.1 mg L-1) and a DWDS in Norway with minimal residual disinfectant (0.08 ± 0.01 mg L-1). Total mycobacteria and Mycobacterium avium complex (MAC) were quantified by qPCR targeting, respectively, atpE genes and the internal transcribed spacer region. Mycobacteria concentrations in drinking water did not differ between the two systems (P = 0.09; up to 6 × 104 copies L-1) but were higher in the biofilms from the chloraminated DWDS (P = 5 × 10-9; up to 5 × 106 copies cm-2). MAC were not detected in either system. Sequencing of mycobacterial hsp65 genes indicated that the chloraminated DWDS lacked diversity and consisted almost exclusively of M. gordonae. In contrast, there were various novel mycobacteria in the no-residual DWDS. Finally, Mycobacterium- and Methylobacterium-like 16S rRNA genes were often detected simultaneously, though without correlation as previously observed. We conclude that, though residual chloramine may increase mycobacterial biomass in a DWDS, it may also decrease mycobacterial diversity.
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Affiliation(s)
- Michael B Waak
- Department of Civil, Environmental, and Geo-Engineering , University of Minnesota , 500 Pillsbury Dr. SE , Minneapolis , Minnesota 55455 , United States
- Department of Civil and Environmental Engineering , Norwegian University of Science and Technology , S.P. Andersens veg 5 , 7491 Trondheim , Norway
| | - Timothy M LaPara
- Department of Civil, Environmental, and Geo-Engineering , University of Minnesota , 500 Pillsbury Dr. SE , Minneapolis , Minnesota 55455 , United States
- BioTechnology Institute , University of Minnesota , 1479 Gortner Ave. , St. Paul , Minnesota 55108 , United States
| | - Cynthia Hallé
- Department of Civil and Environmental Engineering , Norwegian University of Science and Technology , S.P. Andersens veg 5 , 7491 Trondheim , Norway
| | - Raymond M Hozalski
- Department of Civil, Environmental, and Geo-Engineering , University of Minnesota , 500 Pillsbury Dr. SE , Minneapolis , Minnesota 55455 , United States
- BioTechnology Institute , University of Minnesota , 1479 Gortner Ave. , St. Paul , Minnesota 55108 , United States
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Waak MB, Hozalski RM, Hallé C, LaPara TM. Comparison of the microbiomes of two drinking water distribution systems-with and without residual chloramine disinfection. Microbiome 2019; 7:87. [PMID: 31174608 PMCID: PMC6556008 DOI: 10.1186/s40168-019-0707-5] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 05/28/2019] [Indexed: 05/10/2023]
Abstract
BACKGROUND Residual disinfection is often used to suppress biological growth in drinking water distribution systems (DWDSs), but not without undesirable side effects. In this study, water-main biofilms, drinking water, and bacteria under corrosion tubercles were analyzed from a chloraminated DWDS (USA) and a no-residual DWDS (Norway). Using quantitative real-time PCR, we quantified bacterial 16S rRNA genes and ammonia monooxygenase genes (amoA) of Nitrosomonas oligotropha and ammonia-oxidizing archaea-organisms that may contribute to chloramine loss. PCR-amplified 16S rRNA genes were sequenced to assess community taxa and diversity. RESULTS The chloraminated DWDS had lower biofilm biomass (P=1×10-6) but higher N. oligotropha-like amoA genes (P=2×10-7) than the no-residual DWDS (medians =4.7×104 and 1.1×103amoA copies cm-2, chloraminated and no residual, respectively); archaeal amoA genes were only detected in the no-residual DWDS (median =2.8×104 copies cm-2). Unlike the no-residual DWDS, biofilms in the chloraminated DWDS had lower within-sample diversity than the corresponding drinking water (P<1×10-4). Chloramine was also associated with biofilms dominated by the genera, Mycobacterium and Nitrosomonas (≤91.7% and ≤39.6% of sequences, respectively). Under-tubercle communities from both systems contained corrosion-associated taxa, especially Desulfovibrio spp. (≤98.4% of sequences). CONCLUSIONS Although residual chloramine appeared to decrease biofilm biomass and alpha diversity as intended, it selected for environmental mycobacteria and Nitrosomonas oligotropha-taxa that may pose water quality challenges. Drinking water contained common freshwater plankton and did not resemble corresponding biofilm communities in either DWDS; monitoring of tap water alone may therefore miss significant constituents of the DWDS microbiome. Corrosion-associated Desulfovibrio spp. were observed under tubercles in both systems but were particularly dominant in the chloraminated DWDS, possibly due to the addition of sulfate from the coagulant alum.
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Affiliation(s)
- Michael B. Waak
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr SE, Minneapolis, 55455 MN USA
- Department of Civil and Environmental Engineering, Norwegian University of Science and Technology, S. P. Andersens veg 5, Trondheim, 7491 Norway
| | - Raymond M. Hozalski
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr SE, Minneapolis, 55455 MN USA
- BioTechnology Institute, University of Minnesota, 1479 Gortner Ave, Saint Paul, 55108 MN USA
| | - Cynthia Hallé
- Department of Civil and Environmental Engineering, Norwegian University of Science and Technology, S. P. Andersens veg 5, Trondheim, 7491 Norway
| | - Timothy M. LaPara
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr SE, Minneapolis, 55455 MN USA
- BioTechnology Institute, University of Minnesota, 1479 Gortner Ave, Saint Paul, 55108 MN USA
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Aggarwal S, Gomez-Smith CK, Jeon Y, LaPara TM, Waak MB, Hozalski RM. Effects of Chloramine and Coupon Material on Biofilm Abundance and Community Composition in Bench-Scale Simulated Water Distribution Systems and Comparison with Full-Scale Water Mains. Environ Sci Technol 2018; 52:13077-13088. [PMID: 30351033 DOI: 10.1021/acs.est.8b02607] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The vast majority of bacteria in drinking water distribution systems (DWDSs) reside in biofilms on the interior walls of water mains. Little is known about how water quality conditions affect water-main biofilms because of the inherent limitations in experimenting with drinking water supplies and accessing the water mains for sampling. Bench-scale reactors permit experimentation and ease of biofilm sampling, yet questions remain as to how well biofilms in laboratory reactors represent those on water mains. In this study, the effects of DWDS pipe materials and chloramine residual on biofilms were investigated by cultivating biofilms on cement, polyvinyl chloride, and high density polyethylene coupons in CDC reactors for up to 28 months in the presence of chloraminated or dechlorinated tap water. The bench-scale biofilm microbiomes were then compared with the microbiome on a water main from the full-scale system that supplied the water to the reactors. The presence of a chloramine residual (1.74 ± 0.21 mg/L) suppressed biofilm accumulation and selected for Mycobacterium-like and Sphingopyxis-like operational taxonomic units (OTUs) while the destruction of the chloramine residual resulted in a significant increase in biomass quantity and a shift toward a more diverse community dominated by Nitrospira-like OTUs, which, our results suggest, may be complete ammonia oxidizers (comammox). Coupon material, however, had a relatively minor effect on the abundance and community composition of the biofilm bacteria. Although biofilm communities from the chloraminated water reactor and the water mains shared some dominant populations (namely, Mycobacterium- and Nitrosomonas-like OTUs), the communities were significantly different. This manuscript provides novel insights into the effects of dechlorination and pipe material on biofilm community composition. Furthermore, to our knowledge, it is the first study to compare biofilm in a tap water-fed, bench-scale simulated distribution system to biofilm on water mains from the full-scale system supplying the tap water.
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Affiliation(s)
- Srijan Aggarwal
- Department of Civil and Environmental Engineering , University of Alaska Fairbanks , Fairbanks , Alaska 99775 , United States
| | - C Kimloi Gomez-Smith
- Department of Civil, Environmental, and Geo-Engineering , University of Minnesota , Minneapolis , Minnesota 55455 , United States
| | - Youchul Jeon
- Department of Civil and Environmental Engineering , University of Toledo , Toledo , Ohio 43606-339 , United States
| | - Timothy M LaPara
- Department of Civil, Environmental, and Geo-Engineering , University of Minnesota , Minneapolis , Minnesota 55455 , United States
- BioTechnology Institute , University of Minnesota , St. Paul , Minnesota 55108 , United States
| | - Michael B Waak
- Department of Civil and Environmental Engineering , Norwegian University of Science and Technology , 7491 Trondheim , Norway
| | - Raymond M Hozalski
- Department of Civil, Environmental, and Geo-Engineering , University of Minnesota , Minneapolis , Minnesota 55455 , United States
- BioTechnology Institute , University of Minnesota , St. Paul , Minnesota 55108 , United States
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14
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Kerrigan JF, Sandberg KD, Engstrom DR, LaPara TM, Arnold WA. Small and large-scale distribution of four classes of antibiotics in sediment: association with metals and antibiotic resistance genes. Environ Sci Process Impacts 2018; 20:1167-1179. [PMID: 30043816 DOI: 10.1039/c8em00190a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Antibiotic chemicals and antibiotic resistance genes enter the environment via wastewater effluents as well as from runoff from agricultural operations. The relative importance of these two sources, however, is largely unknown. The relationship between the concentrations of chemicals and genes requires exploration, for antibiotics in the environment may lead to development or retention of resistance genes by bacteria. The genes that confer resistance to metal toxicity may also be important in antibiotic resistance. In this work, concentrations of 19 antibiotics (using liquid chromatography tandem mass spectrometry), 14 metals (using inductively coupled plasma-mass spectrometry), and 45 metal, antibiotic, and antibiotic-resistance associated genes (using a multiplex, microfluidic quantitative polymerase chain reaction method) were measured in 13 sediment samples from two large rivers as well as along a spatial transect in a wastewater effluent-impacted lake. Nine of the antibiotics were detected in the rivers and 13 were detected in the lake. Sixteen different resistance genes were detected. The surrounding land use and proximity to wastewater treatment plants are important factors in the number and concentrations of antibiotics detected. Correlations among antibiotic chemical concentrations, metal concentrations, and resistance genes occur over short spatial scales in a lake but not over longer distances in major rivers. The observed correlations likely result from the chemicals and resistance genes arising from the same source, and differences in fate and transport over larger scales lead to loss of this relationship.
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Affiliation(s)
- Jill F Kerrigan
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, MN 55455, USA.
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15
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Waak MB, LaPara TM, Hallé C, Hozalski RM. Occurrence of Legionella spp. in Water-Main Biofilms from Two Drinking Water Distribution Systems. Environ Sci Technol 2018; 52:7630-7639. [PMID: 29902377 DOI: 10.1021/acs.est.8b01170] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The maintenance of a chlorine or chloramine residual to suppress waterborne pathogens in drinking water distribution systems is common practice in the United States but less common in Europe. In this study, we investigated the occurrence of Bacteria and Legionella spp. in water-main biofilms and tap water from a chloraminated distribution system in the United States and a system in Norway with no residual using real-time quantitative polymerase chain reaction (qPCR). Despite generally higher temperatures and assimilable organic carbon levels in the chloraminated system, total Bacteria and Legionella spp. were significantly lower in water-main biofilms and tap water of that system ( p < 0.05). Legionella spp. were not detected in the biofilms of the chloraminated system (0 of 35 samples) but were frequently detected in biofilms from the no-residual system (10 of 23 samples; maximum concentration = 7.8 × 104 gene copies cm-2). This investigation suggests water-main biofilms may serve as a source of Legionella for tap water and premise plumbing systems, and residual chloramine may aid in reducing their abundance.
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Affiliation(s)
- Michael B Waak
- Department of Civil, Environmental, and Geo-Engineering , University of Minnesota , 500 Pillsbury Drive Southeast , Minneapolis , Minnesota 55455 , United States
| | - Timothy M LaPara
- Department of Civil, Environmental, and Geo-Engineering , University of Minnesota , 500 Pillsbury Drive Southeast , Minneapolis , Minnesota 55455 , United States
- BioTechnology Institute , University of Minnesota , 1479 Gortner Avenue , Saint Paul , Minnesota 55108 , United States
| | - Cynthia Hallé
- Department of Civil and Environmental Engineering , Norwegian University of Science and Technology , S.P. Andersens veg 5 , Trondheim NO-7491 , Norway
| | - Raymond M Hozalski
- Department of Civil, Environmental, and Geo-Engineering , University of Minnesota , 500 Pillsbury Drive Southeast , Minneapolis , Minnesota 55455 , United States
- BioTechnology Institute , University of Minnesota , 1479 Gortner Avenue , Saint Paul , Minnesota 55108 , United States
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16
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Kerrigan JF, Sandberg KD, Engstrom DR, LaPara TM, Arnold WA. Sedimentary record of antibiotic accumulation in Minnesota Lakes. Sci Total Environ 2018; 621:970-979. [PMID: 29074236 DOI: 10.1016/j.scitotenv.2017.10.130] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 10/13/2017] [Accepted: 10/13/2017] [Indexed: 05/22/2023]
Abstract
The widespread detection of antibiotics in the environment is concerning because antibiotics are designed to be effective at small doses. The objective of this work was to quantify the accumulation rates of antibiotics used by humans and animals, spanning several major antibiotic classes (sulfonamides, tetracyclines, fluoroquinolones, and macrolides), in Minnesota lake-sediment cores. Our goal was to determine temporal trends, the major anthropogenic source to these lacustrine systems, and the importance of natural production. A historical record of usage trends for ten human and/or animal-use antibiotics (four sulfonamides, three fluoroquinolones, one macrolide, trimethoprim, and lincomycin) was faithfully captured in the sediment cores. Nine other antibiotics were not detected. Ofloxacin, trimethoprim, sulfapyridine, and sulfamethazine were detected in all of the anthropogenically-impacted studied lakes. Maximum sediment fluxes reached 20.5ngcm-2yr-1 (concentration 66.1ng/g) for ofloxacin, 1.2ngcm-2yr-1 (1.2ng/g) for trimethoprim, 3.3ngcm-2yr-1 (11.3ng/g) for sulfapyridine, and 1.0ngcm-2yr-1 (1.6ng/g) for sulfamethazine, respectively. Natural production of lincomycin may have occurred in one lake at fluxes ranging from 0.4 to 1.8ngcm-2yr-1 (0.1 to 5.8ng/g). Wastewater effluent appears to be the primary source of antibiotics in the studied lakes, with lesser inputs from agricultural activities.
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Affiliation(s)
- Jill F Kerrigan
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, MN 55455, United States
| | - Kyle D Sandberg
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, MN 55455, United States
| | - Daniel R Engstrom
- St. Croix Watershed Research Station, Science Museum of Minnesota, 16910 152nd Street North, Marine on St. Croix, MN 55047, United States
| | - Timothy M LaPara
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, MN 55455, United States
| | - William A Arnold
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, MN 55455, United States.
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17
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Burch TR, Sadowsky MJ, LaPara TM. Effect of Different Treatment Technologies on the Fate of Antibiotic Resistance Genes and Class 1 Integrons when Residual Municipal Wastewater Solids are Applied to Soil. Environ Sci Technol 2017; 51:14225-14232. [PMID: 29148730 DOI: 10.1021/acs.est.7b04760] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Residual wastewater solids are a significant reservoir of antibiotic resistance genes (ARGs). While treatment technologies can reduce ARG levels in residual wastewater solids, the effects of these technologies on ARGs in soil during subsequent land-application are unknown. In this study we investigated the use of numerous treatment technologies (air drying, aerobic digestion, mesophilic anaerobic digestion, thermophilic anaerobic digestion, pasteurization, and alkaline stabilization) on the fate of ARGs and class 1 integrons in wastewater solids-amended soil microcosms. Six ARGs [erm(B), qnrA, sul1, tet(A), tet(W), and tet(X)], the integrase gene of class 1 integrons (intI1), and 16S rRNA genes were quantified using quantitative polymerase chain reaction. The quantities of ARGs and intI1 decreased in all microcosms, but thermophilic anaerobic digestion, alkaline stabilization, and pasteurization led to the most extensive decay of ARGs and intI1, often to levels similar to that of the control microcosms to which no wastewater solids had been applied. In contrast, the rates by which ARGs and intI1 declined using the other treatment technologies were generally similar, typically varying by less than 2 fold. These results demonstrate that wastewater solids treatment technologies can be used to decrease the persistence of ARGs and intI1 during their subsequent application to soil.
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Affiliation(s)
- Tucker R Burch
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Michael J Sadowsky
- Biotechnology Institute, University of Minnesota , St. Paul, Minnesota 55108, United States
- Department of Soil, Water, and Climate, University of Minnesota , St. Paul, Minnesota 55108, United States
- Department of Plant and Microbial Biology, University of Minnesota , St. Paul, Minnesota 55108, United States
| | - Timothy M LaPara
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States
- Biotechnology Institute, University of Minnesota , St. Paul, Minnesota 55108, United States
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18
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Sandberg KD, LaPara TM. The fate of antibiotic resistance genes and class 1 integrons following the application of swine and dairy manure to soils. FEMS Microbiol Ecol 2016; 92:fiw001. [PMID: 26738555 DOI: 10.1093/femsec/fiw001] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/22/2015] [Indexed: 01/25/2023] Open
Abstract
The goal of this study was to determine the fate of antibiotic resistance genes (ARGs) and class 1 integrons following the application of swine and dairy manure to soil. Soil microcosms were amended with either manure from swine fed subtherapeutic levels of antibiotics or manure from dairy cows that were given antibiotics only rarely and strictly for veterinary purposes. Microcosms were monitored for 6 months using quantitative PCR targeting 16S rRNA genes (a measure of bacterial biomass), intI1, erm(B), tet(A), tet(W) and tet(X). Swine manure had 10- to 100-fold higher levels of ARGs than the dairy manure, all of which decayed over time after being applied to soil. A modified Collins-Selleck model described the decay of ARGs in the soil microcosms well, particularly the characteristic in which the decay rate declined over time. By the completion of the soil microcosm experiments, ARGs in the dairy manure-amended soils returned to background levels, whereas the ARGs in swine manure remained elevated compared to control microcosms. Our research suggests that the use of subtherapeutic use of antibiotics in animal feed could lead to the accumulation of ARGs in soils to which manure is applied.
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Affiliation(s)
- Kyle D Sandberg
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Timothy M LaPara
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, Minneapolis, MN 55455, USA University of Minnesota, Biotechnology Institute, St. Paul, MN 55108, USA
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McNamara PJ, LaPara TM, Novak PJ. The Effect of Perfluorooctane Sulfonate, Exposure Time, and Chemical Mixtures on Methanogenic Community Structure and Function. Microbiol Insights 2015; 8:1-7. [PMID: 26462249 PMCID: PMC4589087 DOI: 10.4137/mbi.s31345] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 09/01/2015] [Accepted: 09/02/2015] [Indexed: 11/30/2022] Open
Abstract
A plethora of organic micropollutant mixtures are found in untreated municipal wastewater. Anaerobic digesters receive large loadings of hydrophobic micropollutants that sorb to wastewater biosolids. Despite micropollutants being pervasive as mixtures, little research is available to explain the impact that mixtures of compounds, as well as exposure time, have on microbial communities in anaerobic digesters. Perfluorooctane sulfonate (PFOS) was added to anaerobic enrichment cultures in both short-term (14 days) and long-term (140 days) studies to determine the impact of exposure time. Additionally, triclosan was added during the experiments to investigate the impact of mixtures on community structure and function. PFOS did not alter methane production in short-term studies, but in long-term studies, methane production increased, consistent with our hypothesis that PFOS may act as a metabolic uncoupler. The impact of triclosan on methane production was exacerbated when PFOS was already present in the anaerobic enrichment cultures. Triclosan also had greater impacts on microbial community structures in the bottles that had been exposed to PFOS long-term. These results demonstrate that both chemical mixtures and exposure time are important parameters to address when trying to define the impacts of micropollutants on anaerobic microbial communities.
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Affiliation(s)
- Patrick J McNamara
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Timothy M LaPara
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Paige J Novak
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, Minneapolis, MN, USA
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20
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LaPara TM, Madson M, Borchardt S, Lang KS, Johnson TJ. Multiple Discharges of Treated Municipal Wastewater Have a Small Effect on the Quantities of Numerous Antibiotic Resistance Determinants in the Upper Mississippi River. Environ Sci Technol 2015; 49:11509-11515. [PMID: 26325533 DOI: 10.1021/acs.est.5b02803] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This study evaluated multiple discharges of treated wastewater on the quantities of antibiotic resistance genes (ARGs) in the Upper Mississippi River. Surface water and treated wastewater samples were collected along the Mississippi River during three different periods of 4 days during the summer of 2012, and quantitative real-time PCR (qPCR) was used to enumerate several ARGs and related targets. Even though the wastewater effluents contained 75- to 831-fold higher levels of ARGs than the river water, the quantities of ARGs in the Mississippi River did not increase with downstream distance. Plasmids from the incompatibility group A/C were detected at low levels in the wastewater effluents but not in the river water; synthetic DNA containing an ampicillin resistance gene (bla) from cloning vectors was not detected in either the wastewater effluent or river samples. A simple 1D model suggested that the primary reason for the small impact of the wastewater discharges on ARG levels was the large flow rate of the Mississippi River compared to that of the wastewater discharges. Furthermore, this model generally overpredicted the ARG levels in the Mississippi River, suggesting that substantial loss mechanisms (e.g., decay or deposition) were occurring in the river.
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Affiliation(s)
- Timothy M LaPara
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Matthew Madson
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Spencer Borchardt
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States
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21
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Gomez-Smith CK, LaPara TM, Hozalski RM. Sulfate Reducing Bacteria and Mycobacteria Dominate the Biofilm Communities in a Chloraminated Drinking Water Distribution System. Environ Sci Technol 2015; 49:8432-8440. [PMID: 26098899 DOI: 10.1021/acs.est.5b00555] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The quantity and composition of bacterial biofilms growing on 10 water mains from a full-scale chloraminated water distribution system were analyzed using real-time PCR targeting the 16S rRNA gene and next-generation, high-throughput Illumina sequencing. Water mains with corrosion tubercles supported the greatest amount of bacterial biomass (n = 25; geometric mean = 2.5 × 10(7) copies cm(-2)), which was significantly higher (P = 0.04) than cement-lined cast-iron mains (n = 6; geometric mean = 2.0 × 10(6) copies cm(-2)). Despite spatial variation of community composition and bacterial abundance in water main biofilms, the communities on the interior main surfaces were surprisingly similar, containing a core group of operational taxonomic units (OTUs) assigned to only 17 different genera. Bacteria from the genus Mycobacterium dominated all communities at the main wall-bulk water interface (25-78% of the community), regardless of main age, estimated water age, main material, and the presence of corrosion products. Further sequencing of the mycobacterial heat shock protein gene (hsp65) provided species-level taxonomic resolution of mycobacteria. The two dominant Mycobacteria present, M. frederiksbergense (arithmetic mean = 85.7% of hsp65 sequences) and M. aurum (arithmetic mean = 6.5% of hsp65 sequences), are generally considered to be nonpathogenic. Two opportunistic pathogens, however, were detected at low numbers: M. hemophilum (arithmetic mean = 1.5% of hsp65 sequences) and M. abscessus (arithmetic mean = 0.006% of hsp65 sequences). Sulfate-reducing bacteria from the genus Desulfovibrio, which have been implicated in microbially influenced corrosion, dominated all communities located underneath corrosion tubercules (arithmetic mean = 67.5% of the community). This research provides novel insights into the quantity and composition of biofilms in full-scale drinking water distribution systems, which is critical for assessing the risks to public health and to the water supply infrastructure.
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Affiliation(s)
- C Kimloi Gomez-Smith
- †Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
- ‡Water Resources Sciences Graduate Program, University of Minnesota, St. Paul, Minnesota 55108, United States
| | - Timothy M LaPara
- †Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
- §BioTechnology Institute, University of Minnesota, St. Paul, Minnesota 55108, United States
| | - Raymond M Hozalski
- †Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
- §BioTechnology Institute, University of Minnesota, St. Paul, Minnesota 55108, United States
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Ghosh S, LaPara TM, Sadowsky MJ. Transformation of tetracycline by TetX and its subsequent degradation in a heterologous host. FEMS Microbiol Ecol 2015; 91:fiv059. [DOI: 10.1093/femsec/fiv059] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/23/2015] [Indexed: 01/15/2023] Open
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McNamara PJ, LaPara TM, Novak PJ. The impacts of triclosan on anaerobic community structures, function, and antimicrobial resistance. Environ Sci Technol 2014; 48:7393-7400. [PMID: 24915110 DOI: 10.1021/es501388v] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Triclosan is a widespread antimicrobial agent that accumulates in anaerobic digesters used to treat the residual solids generated at municipal wastewater treatment plants; there is very little information, however, about how triclosan impacts microbial communities in anaerobic digesters. We investigated how triclosan impacts the community structure, function and antimicrobial resistance genes in lab-scale anaerobic digesters. Previously exposed (to triclosan) communities were amended with 5, 50, and 500 mg/kg of triclosan, corresponding to the median, 95th percentile, and 4-fold higher than maximum triclosan concentration that has been detected in U.S. biosolids. Triclosan amendment caused all of the Bacteria and Archaea communities to structurally diverge from that of the control cultures (based on ARISA). At the end of the experiment, all triclosan-amended Archaea communities had diverged from the control communities, regardless of the triclosan concentration added. In contrast, over time the Bacteria communities that were amended with lower concentrations of triclosan (5 mg/kg and 50 mg/kg) initially diverged and then reconverged with the control community structure. Methane production at 500 mg/kg was nearly half the methane production in control cultures. At 50 mg/kg, a large variability in methane production was observed, suggesting that 50 mg/kg may be a tipping point where function begins to fail in some communities. When previously unexposed communities were exposed to 500 mg triclosan/kg, function was maintained, but the abundance of a gene encoding for triclosan resistance (mexB) increased. This research suggests that triclosan could inhibit methane production in anaerobic digesters if concentrations were to increase and may also select for resistant Bacteria. In both cases, microbial community composition and exposure history alter the influence of triclosan.
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Affiliation(s)
- Patrick J McNamara
- Department of Civil Engineering, University of Minnesota , 500 Pillsbury Drive SE, Minneapolis, Minnesota 55455, United States
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Burch TR, Sadowsky MJ, LaPara TM. Fate of antibiotic resistance genes and class 1 integrons in soil microcosms following the application of treated residual municipal wastewater solids. Environ Sci Technol 2014; 48:5620-5627. [PMID: 24762092 DOI: 10.1021/es501098g] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Substantial quantities of antibiotic resistance genes (ARGs) are discharged with treated residual municipal wastewater solids and subsequently applied to soil. The objective of this work was to determine the decay rates for ARGs and class 1 integrons following simulated land application of treated wastewater solids. Treated residual solids from two full-scale treatment plants were applied to sets of triplicate soil microcosms in two independent experiments. Experiment 1 investigated loading rates of 20, 40, and 100 g kg(-1) of residual solids to a sandy soil, while experiment 2 investigated a loading rate of 40 g kg(-1) to a silty-loamy soil. Five ARGs (erm(B), sul1, tet(A), tet(W), and tet(X)), the integrase of class 1 integrons (intI1), 16S rRNA genes, 16S rRNA genes of all Bacteroides spp., and 16S rRNA genes of human-specific Bacteroides spp. were quantified using real-time polymerase chain reaction. ARGs and intI1 quantities declined in most microcosms, with statistically significant (P < 0.05) half-lives varying between 13 d (erm(B), experiment 1, 100 g kg(-1)) and 81 d (intI1, experiment 1, 40 g kg(-1)). These kinetic rates were much slower than have been previously reported for unit operations used to treat wastewater solids (e.g., anaerobic digestion). This research suggests that the design and operation of municipal wastewater treatment facilities with the explicit goal of mitigating the release of ARGs should focus on using technologies within the treatment facility, rather than depending on attenuation subsequent to land application.
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Affiliation(s)
- Tucker R Burch
- Department of Civil Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States
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Burch TR, Sadowsky MJ, LaPara TM. Air-drying beds reduce the quantities of antibiotic resistance genes and class 1 integrons in residual municipal wastewater solids. Environ Sci Technol 2013; 47:9965-9971. [PMID: 23909386 DOI: 10.1021/es4024749] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
This study investigated whether air-drying beds reduce antibiotic resistance gene (ARG) concentrations in residual municipal wastewater solids. Three laboratory-scale drying beds were operated for a period of nearly 100 days. Real-time PCR was used to quantify 16S rRNA genes, 16S rRNA genes specific to fecal bacteria (AllBac) and human fecal bacteria (HF183), the integrase gene of class 1 integrons (intI1), and five ARGs representing a cross-section of antibiotic classes and resistance mechanisms (erm(B), sul1, tet(A), tet(W), and tet(X)). Air-drying beds were capable of reducing all gene target concentrations by 1 to 5 orders of magnitude, and the nature of this reduction was consistent with both a net decrease in the number of bacterial cells and a lack of selection within the microbial community. Half-lives varied between 1.5 d (HF183) and 5.4 d (tet(X)) during the first 20 d of treatment. After the first 20 d of treatment, however, half-lives varied between 8.6 d (tet(X)) and 19.3 d (AllBac), and 16S rRNA gene, intI1, and sul1 concentrations did not change (P > 0.05). These results demonstrate that air-drying beds can reduce ARG and intI1 concentrations in residual municipal wastewater solids within timeframes typical of operating practices.
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MESH Headings
- Anti-Bacterial Agents/analysis
- Anti-Bacterial Agents/pharmacology
- Bacteria/genetics
- Bacteria/isolation & purification
- Bacteria/metabolism
- Bacterial Proteins/analysis
- Bacterial Proteins/genetics
- Bacterial Proteins/metabolism
- Drug Resistance, Microbial
- Integrons
- RNA, Ribosomal, 16S/genetics
- RNA, Ribosomal, 16S/isolation & purification
- RNA, Ribosomal, 16S/metabolism
- Real-Time Polymerase Chain Reaction
- Waste Disposal, Fluid/methods
- Wastewater/analysis
- Wastewater/microbiology
- Water Pollutants, Chemical/analysis
- Water Pollutants, Chemical/pharmacology
- Water Pollution, Chemical/prevention & control
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Affiliation(s)
- Tucker R Burch
- Department of Civil Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States
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Ling AL, Pace NR, Hernandez MT, LaPara TM. Tetracycline resistance and Class 1 integron genes associated with indoor and outdoor aerosols. Environ Sci Technol 2013; 47:4046-52. [PMID: 23517146 DOI: 10.1021/es400238g] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Genes encoding tetracycline resistance and the integrase of Class 1 integrons were enumerated using quantitative PCR from aerosols collected from indoor and outdoor environments. Concentrated animal feeding operations (CAFOs) and human-occupied indoor environments (two clinics and a homeless shelter) were found to be a source of airborne tet(X) and tet(W) genes. The CAFOs had 10- to 100-times higher concentrations of airborne 16S rRNA, tet(X), and tet(W) genes than other environments sampled, and increased concentrations of aerosolized bacteria correlated with increased concentrations of airborne resistance genes. The two CAFOs studied had statistically similar concentrations of resistance genes in their aerosol samples, even though antibiotic use was markedly different between the two operations. Additionally, tet(W) genes were recovered in outdoor air within 2 km of livestock operations, which suggests that antibiotic resistance genes may be transported via aerosols on local scales. The integrase gene (intI1) from Class 1 integrons, which has been associated with multidrug resistance, was detected in CAFOs but not in human-occupied indoor environments, suggesting that CAFO aerosols could serve as a reservoir of multidrug resistance. In conclusion, our results show that CAFOs and clinics are sources of aerosolized antibiotic resistance genes that can potentially be transported via air movement.
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Affiliation(s)
- Alison L Ling
- Department of Civil, Environmental, and Agricultural Engineering, University of Colorado, Boulder, Colorado 80309, USA
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Wunder DB, Tan DT, LaPara TM, Hozalski RM. The effects of antibiotic cocktails at environmentally relevant concentrations on the community composition and acetate biodegradation kinetics of bacterial biofilms. Chemosphere 2013; 90:2261-2266. [PMID: 23159070 DOI: 10.1016/j.chemosphere.2012.10.031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Revised: 10/15/2012] [Accepted: 10/16/2012] [Indexed: 06/01/2023]
Abstract
Antibiotics and antibacterials are present in water bodies worldwide but little is known about their effects on the biological processes often used to treat water. In this research, the effect of antibiotics on bacterial activity and community structure was investigated by growing biofilms in the presence and absence of a mixture of three compounds (sulfamethoxazole, erythromycin, and ciprofloxacin) in a continuous-flow rotating annular bioreactor fed acetate as a carbon and energy source. Steady-state, surface area-normalized substrate utilization rates for all antibiotic treatments (all at 0.33 μg L(-1), all at 3.33 μg L(-1), and 1 at 3.33 μg L(-1) with the other 2 at 0.33 μg L(-1)) were similar to the control experiments. Higher attached biomass levels in the experiments with ciprofloxacin at 3.33 μg L(-1) resulted in lower steady-state biomass-normalized substrate utilization rates in comparison to other runs. Microbial community analyses via automated ribosomal intergenic spacer analysis revealed significant shifts in community structure for the experiments dosed with the highest concentrations of ciprofloxacin, suggesting that the antibiotic selected for more resistant bacterial strains. The results of this research also suggest that mixtures of antibiotics at the sub-μg L(-1) concentrations typically observed in surface waters are unlikely to affect biological process performance, at least in terms of the degradation of easily assimilable compounds. Conversely, changes to community structure and biofilm quantity might be expected with ciprofloxacin at μg L(-1) concentrations.
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Affiliation(s)
- David B Wunder
- Calvin College, Department of Engineering, Grand Rapids, MI 49546-4493, USA.
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LaPara TM, Burch TR, McNamara PJ, Tan DT, Yan M, Eichmiller JJ. Tertiary-treated municipal wastewater is a significant point source of antibiotic resistance genes into Duluth-Superior Harbor. Environ Sci Technol 2011; 45:9543-9. [PMID: 21981654 DOI: 10.1021/es202775r] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
In this study, the impact of tertiary-treated municipal wastewater on the quantity of several antibiotic resistance determinants in Duluth-Superior Harbor was investigated by collecting surface water and sediment samples from 13 locations in Duluth-Superior Harbor, the St. Louis River, and Lake Superior. Quantitative PCR (qPCR) was used to target three different genes encoding resistance to tetracycline (tet(A), tet(X), and tet(W)), the gene encoding the integrase of class 1 integrons (intI1), and total bacterial abundance (16S rRNA genes) as well as total and human fecal contamination levels (16S rRNA genes specific to the genus Bacteroides ). The quantities of tet(A), tet(X), tet(W), intI1, total Bacteroides , and human-specific Bacteroides were typically 20-fold higher in the tertiary-treated wastewater than in nearby surface water samples. In contrast, the quantities of these genes in the St. Louis River and Lake Superior were typically below detection. Analysis of sequences of tet(W) gene fragments from four different samples collected throughout the study site supported the conclusion that tertiary-treated municipal wastewater is a point source of resistance genes into Duluth-Superior Harbor. This study demonstrates that the discharge of exceptionally treated municipal wastewater can have a statistically significant effect on the quantities of antibiotic resistance genes in otherwise pristine surface waters.
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Affiliation(s)
- Timothy M LaPara
- Department of Civil Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States.
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Diehl DL, LaPara TM. Effect of temperature on the fate of genes encoding tetracycline resistance and the integrase of class 1 integrons within anaerobic and aerobic digesters treating municipal wastewater solids. Environ Sci Technol 2010; 44:9128-33. [PMID: 21058743 DOI: 10.1021/es102765a] [Citation(s) in RCA: 205] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The objective of this research was to investigate the ability of anaerobic and aerobic digesters to reduce the quantity of antibiotic resistant bacteria in wastewater solids. Lab-scale digesters were operated at different temperatures (22 °C, 37 °C, 46 °C, and 55 °C) under both anaerobic and aerobic conditions and fed wastewater solids collected from a full-scale treatment facility. Quantitative PCR was used to track five genes encoding tetracycline resistance (tet(A), tet(L), tet(O), tet(W), and tet(X)) and the gene encoding the integrase (intI1) of class 1 integrons. Statistically significant reductions in the quantities of these genes occurred in the anaerobic reactors at 37 °C, 46 °C, and 55 °C, with the removal rates and removal efficiencies increasing as a function of temperature. The aerobic digesters, in contrast, were generally incapable of significantly decreasing gene quantities, although these digesters were operated at much shorter mean hydraulic residence times. This research suggests that high temperature anaerobic digestion of wastewater solids would be a suitable technology for eliminating various antibiotic resistance genes, an emerging pollutant of concern.
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Affiliation(s)
- David L Diehl
- Department of Civil Engineering, University of Minnesota, 500 Pillsbury Drive SE, Minneapolis, Minnesota 55455-0116, United States
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Zhang P, Hozalski RM, Leach LH, Camper AK, Goslan EH, Parsons SA, Xie YF, LaPara TM. Isolation and characterization of haloacetic acid-degradingAfipiaspp. from drinking water. FEMS Microbiol Lett 2009; 297:203-8. [DOI: 10.1111/j.1574-6968.2009.01687.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Ghosh S, Ramsden SJ, LaPara TM. The role of anaerobic digestion in controlling the release of tetracycline resistance genes and class 1 integrons from municipal wastewater treatment plants. Appl Microbiol Biotechnol 2009; 84:791-6. [PMID: 19597810 DOI: 10.1007/s00253-009-2125-2] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2009] [Revised: 06/29/2009] [Accepted: 06/30/2009] [Indexed: 11/28/2022]
Abstract
In this study, the abilities of two anaerobic digestion processes used for sewage sludge stabilization were compared for their ability to reduce the quantities of three genes that encode resistance to tetracycline (tet(A), tet(O), and tet(X)) and one gene involved with integrons (intI1). A two-stage, thermophilic/mesophilic digestion process always resulted in significant decreases in the quantities of tet(X) and intI1, less frequently in decreases of tet(O), and no net decrease in tet(A). The thermophilic stage was primarily responsible for reducing the quantities of these genes, while the subsequent mesophilic stage sometimes caused a rebound in their quantities. In contrast, a conventional anaerobic digestion process rarely caused a significant decrease in the quantities of any of these genes, with significant increases occurring more frequently. Our results demonstrate that anaerobic thermophilic treatment was more efficient in reducing quantities of genes associated with the spread of antibiotic resistance compared to mesophilic digestion.
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Affiliation(s)
- Sudeshna Ghosh
- Department of Civil Engineering, University of Minnesota, 500 Pillsbury Drive SE, Minneapolis, MN 55455-0116, USA
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Ghosh S, Sadowsky MJ, Roberts MC, Gralnick JA, LaPara TM. Sphingobacterium sp. strain PM2-P1-29 harbours a functional tet(X) gene encoding for the degradation of tetracycline. J Appl Microbiol 2009; 106:1336-42. [PMID: 19187139 DOI: 10.1111/j.1365-2672.2008.04101.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIMS The tet(X) gene has previously been found in obligate anaerobic Bacteroides spp., which is curious because tet(X) encodes for a NADP-dependent monooxygenase that requires oxygen to degrade tetracycline. In this study, we characterized a tetracycline resistant, aerobic, Gram-negative Sphingobacterium sp. strain PM2-P1-29 that harbours a tet(X) gene. METHODS AND RESULTS Sphingobacterium sp. PM2-P1-29 demonstrated the ability to transform tetracycline compared with killed controls. The presence of the tet(X) gene was verified by PCR and nucleotide sequence analysis. Additional nucleotide sequence analysis of regions flanking the tet(X) gene revealed a mobilizable transposon-like element (Tn6031) that shared organizational features and genes with the previously described Bacteroides conjugative transposon CTnDOT. A circular transposition intermediate of the tet(X) region, characteristic of mobilizable transposons, was detected. However, we could not demonstrate the conjugal transfer of the tet(X) gene using three different recipient strains and numerous experimental conditions. CONCLUSIONS This study suggests that Sphingobacterium sp. PM2-P1-29 or a related bacterium may be an ancestral source of the tet(X) gene. SIGNIFICANCE AND IMPACT OF THE STUDY This study demonstrates the importance of environmental bacteria and lateral gene transfer in the dissemination and proliferation of antibiotic resistance among bacteria.
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Affiliation(s)
- S Ghosh
- Department of Civil Engineering, University of Minnesota, Minneapolis, 55455-0116, USA
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Chen RD, Semmens MJ, LaPara TM. Biological treatment of a synthetic space mission wastewater using a membrane-aerated, membrane-coupled bioreactor (M2BR). J Ind Microbiol Biotechnol 2008; 35:465-73. [DOI: 10.1007/s10295-008-0302-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2007] [Accepted: 12/09/2007] [Indexed: 10/22/2022]
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Muñoz-Aguayo J, Lang KS, LaPara TM, González G, Singer RS. Evaluating the effects of chlortetracycline on the proliferation of antibiotic-resistant bacteria in a simulated river water ecosystem. Appl Environ Microbiol 2007; 73:5421-5. [PMID: 17616621 PMCID: PMC2042072 DOI: 10.1128/aem.00708-07] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Antibiotics and antibiotic metabolites have been found in the environment, but the biological activities of these compounds are uncertain, especially given the low levels that are typically detected in the environment. The objective of this study was to estimate the selection potential of chlortetracycline (CTC) on the antibiotic resistance of aerobic bacterial populations in a simulated river water ecosystem. Six replicates of a 10-day experiment using river water in continuous flow chemostat systems were conducted. Each replicate used three chemostats, one serving as a control to which no antibiotic was added and the other two receiving low and high doses of CTC (8 microg/liter and 800 microg/liter, respectively). The addition of CTC to the chemostats did not impact the overall level of cultivable aerobic bacteria (P = 0.51). The high-CTC chemostat had significantly higher tetracycline-resistant bacterial colony counts than both the low-CTC and the control chemostats (P < 0.035). The differences in resistance between the low-CTC and control chemostats were highly nonsignificant (P = 0.779). In general a greater diversity of tet resistance genes was detected in the high-CTC chemostat and with a greater frequency than in the low-CTC and control chemostats. Low levels of CTC in this in vitro experiment did not select for increased levels of tetracycline resistance among cultivable aerobic bacteria. This finding should not be equated with the absence of environmental risk, however. Low concentrations of antibiotics in the environment may select for resistant bacterial populations once they are concentrated in sediments or other locations.
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Affiliation(s)
- Jeannette Muñoz-Aguayo
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, 1971 Commonwealth Avenue, St. Paul, MN 55108, USA
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O'Connor BL, Hondzo M, Dobraca D, LaPara TM, Finlay JC, Brezonik PL. Quantity-activity relationship of denitrifying bacteria and environmental scaling in streams of a forested watershed. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2006jg000254] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Ben L. O'Connor
- Saint Anthony Falls Laboratory; University of Minnesota-Twin Cities; Minneapolis Minnesota USA
| | - Miki Hondzo
- Saint Anthony Falls Laboratory; University of Minnesota-Twin Cities; Minneapolis Minnesota USA
| | - Dina Dobraca
- Department of Genetics, Cell Biology, and Development; University of Minnesota-Twin Cities; Minneapolis Minnesota USA
| | - Timothy M. LaPara
- Department of Civil Engineering; University of Minnesota-Twin Cities; Minneapolis Minnesota USA
| | - Jacques C. Finlay
- Department of Ecology, Evolution, and Behavior; University of Minnesota-Twin Cities; St. Paul Minnesota USA
| | - Patrick L. Brezonik
- Department of Civil Engineering; University of Minnesota-Twin Cities; Minneapolis Minnesota USA
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Yan T, LaPara TM, Novak PJ. The reductive dechlorination of 2,3,4,5-tetrachlorobiphenyl in three different sediment cultures: evidence for the involvement of phylogenetically similar Dehalococcoides-like bacterial populations. FEMS Microbiol Ecol 2006; 55:248-61. [PMID: 16420633 PMCID: PMC2002497 DOI: 10.1111/j.1574-6941.2005.00022.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Anaerobic cultures capable of reductively dechlorinating 2,3,4,5-tetrachlorobiphenyl (CB) were enriched from three different sediments, one estuarine, one marine and one riverine. Two different electron donors were used in enrichments with the estuarine sediment (elemental iron or a mixture of fatty acids). The removal of doubly flanked meta and para chlorines to form 2,3,5-CB and 2,4,5-CB was observed in all cultures. Bacterial community analysis of PCR-amplified 16S rRNA gene fragments revealed different communities in these cultures, with the exception of one common population that showed a high phylogentic relatedness to Dehalococcoides species. No Dehalococcoides-like populations were ever detected in control cultures to which no PCBs were added. In addition, the dynamics of this Dehalococcoides-like population were strongly correlated with dechlorination. Subcultures of the estuarine sediment culture demonstrated that the Dehalococcoides-like population disappeared when dechlorination was inhibited with 2-bromoethanesulfonate or when 2,3,4,5-CB had been consumed. These results provide evidence that Dehalococcoides-like populations were involved in the removal of doubly flanked chlorines from 2,3,4,5-CB. Furthermore, the successful enrichment of these populations from geographically distant and geochemically distinct environments indicates the widespread presence of these PCB-dechlorinating, Dehalococcoides-like organisms.
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Affiliation(s)
- Tao Yan
- Department of Civil Engineering, University of Minnesota, Minneapolis, MN 55455-0116, USA
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Yan T, LaPara TM, Novak PJ. The effect of varying levels of sodium bicarbonate on polychlorinated biphenyl dechlorination in Hudson River sediment cultures. Environ Microbiol 2006; 8:1288-1298. [PMID: 16817937 PMCID: PMC1945130 DOI: 10.1111/j.1462-2920.2006.001037.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The addition of different concentrations of sodium bicarbonate had a profound effect on 2,3,4,5-chlorobiphenyl (2,3,4,5-CB) dechlorination in Hudson River sediment cultures. The most extensive dechlorination was observed in cultures to which 100 mg l(-1) bicarbonate was added. Cultures amended with 1000 mg l(-1) bicarbonate had the least extensive dechlorination, with 2,4-CB and 2,5-CB as predominant end-products. A significant loss of total chlorinated biphenyl mass was observed in cultures to which < or = 500 mg l(-1) bicarbonate was added, suggesting that degradation beyond chlorinated biphenyls occurred. The dynamics of acetate formation were different among the treatments, with high acetate concentrations detected throughout the 303-day experiment in cultures to which 1000 mg l(-1) bicarbonate had been added. Sodium bicarbonate addition also had a significant impact on bacterial community structure as detected by polymerase chain reaction-denaturant gradient gel electrophoresis (PCR-DGGE) of 16S rRNA gene fragments. Three putative polychlorinated biphenyl (PCB) dechlorinators were identified; one Dehalococcoides-like population was detected in all enrichment cultures, whereas two Dehalobacter-like populations were only detected in the enrichment cultures with the most extensive dechlorination. These results suggest that the availability of bicarbonate, and potentially sodium, may affect PCB dechlorination in Hudson River sediment and thus need to be taken into consideration when assessing the fate of PCBs or implementing bioremediation.
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Affiliation(s)
| | | | - Paige J. Novak
- *For correspondence. E-mail ; Tel. (+1) 612 626 9846; Fax (+1) 612 626 7750
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Yan T, LaPara TM, Novak PJ. The effect of varying levels of sodium bicarbonate on polychlorinated biphenyl dechlorination in Hudson River sediment cultures. Environ Microbiol 2006; 8:1288-98. [PMID: 16817937 PMCID: PMC1945130 DOI: 10.1111/j.1462-2920.2006.01037.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The addition of different concentrations of sodium bicarbonate had a profound effect on 2,3,4,5-chlorobiphenyl (2,3,4,5-CB) dechlorination in Hudson River sediment cultures. The most extensive dechlorination was observed in cultures to which 100 mg l(-1) bicarbonate was added. Cultures amended with 1000 mg l(-1) bicarbonate had the least extensive dechlorination, with 2,4-CB and 2,5-CB as predominant end-products. A significant loss of total chlorinated biphenyl mass was observed in cultures to which < or = 500 mg l(-1) bicarbonate was added, suggesting that degradation beyond chlorinated biphenyls occurred. The dynamics of acetate formation were different among the treatments, with high acetate concentrations detected throughout the 303-day experiment in cultures to which 1000 mg l(-1) bicarbonate had been added. Sodium bicarbonate addition also had a significant impact on bacterial community structure as detected by polymerase chain reaction-denaturant gradient gel electrophoresis (PCR-DGGE) of 16S rRNA gene fragments. Three putative polychlorinated biphenyl (PCB) dechlorinators were identified; one Dehalococcoides-like population was detected in all enrichment cultures, whereas two Dehalobacter-like populations were only detected in the enrichment cultures with the most extensive dechlorination. These results suggest that the availability of bicarbonate, and potentially sodium, may affect PCB dechlorination in Hudson River sediment and thus need to be taken into consideration when assessing the fate of PCBs or implementing bioremediation.
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Affiliation(s)
| | | | - Paige J. Novak
- *For correspondence. E-mail ; Tel. (+1) 612 626 9846; Fax (+1) 612 626 7750
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LaPara TM, Klatt CG, Chen R. Adaptations in bacterial catabolic enzyme activity and community structure in membrane-coupled bioreactors fed simple synthetic wastewater. J Biotechnol 2006; 121:368-80. [PMID: 16125815 DOI: 10.1016/j.jbiotec.2005.07.013] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2005] [Revised: 06/30/2005] [Accepted: 07/11/2005] [Indexed: 10/25/2022]
Abstract
Membrane-coupled bioreactors (MBRs) offer substantial benefits compared to conventional reactor designs for biological wastewater treatment. MBR treatment efficiency, however, has not been optimized because the effects of the MBR on process microbiology are poorly understood. In this study, the structure and function of the microbial communities growing in MBRs fed simple synthetic wastewater were investigated. In four starch-fed MBRs, the bacterial community substantially increased its alpha-glucosidase affinity (>1000-fold), while the leucine aminopeptidase and heptanoate esterase affinities increased slightly (<40-fold) or remained relatively constant. Concomitant to these physiological adaptations, shifts in the bacterial community structure in two of the starch-fed MBRs were detected by PCR-DGGE. Four of the bacterial populations detected by PCR-DGGE were isolated and exhibited specific growth rates in batch culture ranging from 0.009 to 0.22 h(-1). Our results suggest that bacterial communities growing under increasingly stringent nutrient limitation adapt their enzyme activities primarily for the nutrients provided, but that there is also a more subtle response not linked to the substrates included in the feed medium. Our research also demonstrates that MBRs can support relatively complex bacterial communities even on simple feed media.
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MESH Headings
- Adaptation, Physiological
- Bacteria, Aerobic/genetics
- Bacteria, Aerobic/growth & development
- Bacteria, Aerobic/metabolism
- Bacteria, Aerobic/physiology
- Biodegradation, Environmental
- Biomass
- Bioreactors/microbiology
- Carbohydrate Metabolism
- Culture Media/metabolism
- Esterases/metabolism
- Leucyl Aminopeptidase/analysis
- Leucyl Aminopeptidase/metabolism
- Membranes, Artificial
- Polymerase Chain Reaction
- Population Dynamics
- Proteins/metabolism
- RNA, Ribosomal, 16S/analysis
- Starch/metabolism
- Substrate Specificity
- Waste Disposal, Fluid/methods
- Water Pollutants, Chemical/metabolism
- alpha-Glucosidases/metabolism
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Affiliation(s)
- Timothy M LaPara
- University of Minnesota, Department of Civil Engineering, 500 Pillsbury Drive SE, MN 55455-0116, USA.
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Chen R, LaPara TM. Aerobic biological treatment of low-strength synthetic wastewater in membrane-coupled bioreactors: the structure and function of bacterial enrichment cultures as the net growth rate approaches zero. Microb Ecol 2006; 51:99-108. [PMID: 16400538 DOI: 10.1007/s00248-005-0081-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2005] [Accepted: 09/13/2005] [Indexed: 05/06/2023]
Abstract
The goal of the current research was to determine if the stringent nutrient limitation imposed by membrane-coupled bioreactors (MBRs) could be used to force mixed bacterial communities to exhibit a zero net growth rate over an extended time period. Mechanistically, this zero net growth rate could be achieved when the amount of energy available for growth is balanced by the maintenance requirements of the bacterial community. Bench-scale MBRs were fed synthetic feed medium containing gelatin as the major organic substrate. Biomass concentrations initially increased rapidly, but subsequently declined until an asymptote was reached. Leucine aminopeptidase activities concomitantly increased by at least 10-fold, suggesting that bacterial catabolic activity remained high even while growth rates became negligible. In contrast, alpha-glucosidase and heptanoate esterase activities decreased, indicating that the bacterial community specifically adapted to the carbon source in the feed medium. Bacterial community analysis by denaturing gradient gel electrophoresis of PCR-amplified 16S rRNA gene fragments (PCR-DGGE) suggested that the bacterial community structure completely changed from the beginning to the end of each MBR. Excision and nucleotide sequence analysis of prominent PCR-DGGE bands suggested that many of the dominant populations were similar to novel bacterial strains that were previously uncultivated or recently cultivated during studies specifically targeting these novel populations. This research demonstrates that MBRs have substantial practical applications for biological wastewater treatment; in addition, MBRs are a useful tool to study the ecology of slow-growing bacteria.
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MESH Headings
- Bacteria, Aerobic/classification
- Bacteria, Aerobic/enzymology
- Bacteria, Aerobic/genetics
- Bacteria, Aerobic/isolation & purification
- Base Sequence
- Biomass
- Bioreactors/microbiology
- Culture Media/metabolism
- DNA, Bacterial/chemistry
- Electrophoresis, Polyacrylamide Gel/methods
- Gelatin/metabolism
- Hydrolysis
- Leucyl Aminopeptidase/analysis
- Leucyl Aminopeptidase/metabolism
- Molecular Sequence Data
- RNA, Ribosomal, 16S/chemistry
- RNA, Ribosomal, 16S/genetics
- Sequence Analysis, DNA
- Waste Disposal, Fluid/methods
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Affiliation(s)
- Ruoyu Chen
- Department of Civil Engineering, University of Minnesota, 500 Pillsbury Drive SE, Minneapolis, MN 55455, USA
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LaPara TM, Cole AC, Shanahan JW, Semmens MJ. The effects of organic carbon, ammoniacal-nitrogen, and oxygen partial pressure on the stratification of membrane-aerated biofilms. J Ind Microbiol Biotechnol 2005; 33:315-23. [PMID: 16292557 DOI: 10.1007/s10295-005-0052-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2005] [Accepted: 09/28/2005] [Indexed: 11/30/2022]
Abstract
The purpose of this study was to examine the effects of different nutrient (carbon, nitrogen, oxygen) concentrations on the microbial activity and community structure in membrane-aerated biofilms (MABs). MABs were grown under well-defined conditions of fluid flow, substrate concentration, and membrane oxygen partial pressure. Biofilms were then removed and thin-sliced using a cryostat/microtome parallel to the membrane. Individual slices were analyzed for changes with depth in biomass density, respiratory activity, and the population densities of ammonia-oxidizing and denitrifying bacteria populations. Oxygen-sensing microelectrodes were used to determine the depth of oxygen penetration into each biofilm. Our results demonstrated that ammonia-oxidizing bacteria grow near the membrane, while denitrifying bacteria grow a substantial distance from the membrane. However, nitrifying and denitrifying bacteria did not grow simultaneously when organic concentrations became too high or ammonia concentrations became too low. In conclusion, membrane-aerated biofilms exhibit substantial stratification with respect to community structure and activity. A fundamental understanding of the factors that control this stratification will help optimize the performance of full-scale membrane-aerated biofilm reactors for wastewater treatment.
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Affiliation(s)
- Timothy M LaPara
- Department of Civil Engineering, University of Minnesota, 122 Civil Engineering, 500 Pillsbury Drive SE, Minneapolis, MN 55455, USA.
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Kappell AS, Semmens MJ, Novak PJ, LaPara TM. Novel application of oxygen-transferring membranes to improve anaerobic wastewater treatment. Biotechnol Bioeng 2005; 89:373-80. [PMID: 15643630 DOI: 10.1002/bit.20219] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Anaerobic biological wastewater treatment has numerous advantages over conventional aerobic processes; anaerobic biotechnologies, however, still have a reputation for low-quality effluents and operational instabilities. In this study, anaerobic bioreactors were augmented with an oxygen-transferring membrane to improve treatment performance. Two anaerobic bioreactors were fed a synthetic high-strength wastewater (chemical oxygen demand, or COD, of 11,000 mg l(-1)) and concurrently operated until biomass concentrations and effluent quality stabilized. Membrane aeration was then initiated in one of these bioreactors, leading to substantially improved COD removal efficiency (> 95%) compared to the unaerated control bioreactor (approximately 65%). The membrane-augmented anaerobic bioreactor required substantially less base addition to maintain circumneutral pH and exhibited 75% lower volatile fatty acid concentrations compared to the unaerated control bioreactor. The membrane-aerated bioreactor, however, failed to improve nitrogenous removal efficiency and produced 80% less biogas than the control bioreactor. A third membrane-augmented anaerobic bioreactor was operated to investigate the impact of start-up procedure on nitrogenous pollutant removal. In this bioreactor, excellent COD (>90%) and nitrogenous (>95%) pollutant removal efficiencies were observed at an intermediate COD concentration (5,500 mg l(-1)). Once the organic content of the influent wastewater was increased to full strength (COD = 11,000 mg l(-1)), however, nitrogenous pollutant removal stopped. This research demonstrates that partial aeration of anaerobic bioreactors using oxygen-transferring membranes is a novel approach to improve treatment performance. Additional research, however, is needed to optimize membrane surface area versus the organic loading rate to achieve the desired effluent quality.
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Affiliation(s)
- Anthony S Kappell
- Department of Civil Engineering, University of Minnesota, 122 Civil Engineering, 500 Pillsbury Drive SE, Minneapolis, MN 55455, USA
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Cole AC, Semmens MJ, LaPara TM. Stratification of activity and bacterial community structure in biofilms grown on membranes transferring oxygen. Appl Environ Microbiol 2004; 70:1982-9. [PMID: 15066788 PMCID: PMC383171 DOI: 10.1128/aem.70.4.1982-1989.2004] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previous studies have shown that membrane-aerated biofilm (MAB) reactors can simultaneously remove carbonaceous and nitrogenous pollutants from wastewater in a single reactor. Oxygen is provided to MABs through gas-permeable membranes such that the region nearest the membrane is rich in oxygen but low in organic carbon, whereas the outer region of the biofilm is void of oxygen but rich in organic carbon. In this study, MABs were grown under similar conditions but at two different fluid velocities (2 and 14 cm s(-1)) across the biofilm. MABs were analyzed for changes in biomass density, respiratory activity, and bacterial community structure as functions of biofilm depth. Biomass density was generally highest near the membrane and declined with distance from the membrane. Respiratory activity exhibited a hump-shaped profile, with the highest activity occurring in the middle of the biofilm. Community analysis by PCR cloning and PCR-denaturing gradient gel electrophoresis of 16S rRNA genes demonstrated substantial stratification of the community structure across the biofilm. Population profiles were also generated by competitive quantitative PCR of gene fragments specific for ammonia-oxidizing bacteria (AOB) (amoA) and denitrifying bacteria (nirK and nirS). At a flow velocity of 14 cm s(-1), AOB were found only near the membrane, whereas denitrifying bacteria proliferated in the anoxic outer regions of the biofilm. In contrast, at a flow velocity of 2 cm s(-1), AOB were either not detected or detected at a concentration near the detection limit. This study suggests that, under the appropriate conditions, both AOB and denitrifying bacteria can coexist within an MAB.
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Affiliation(s)
- Alina C Cole
- Department of Civil Engineering, University of Minnesota, Minneapolis, Minnesota 55455-0116, USA
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Ghosh S, LaPara TM. Removal of carbonaceous and nitrogenous pollutants from a synthetic wastewater using a membrane-coupled bioreactor. J Ind Microbiol Biotechnol 2004; 31:353-61. [PMID: 15338423 DOI: 10.1007/s10295-004-0152-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2003] [Accepted: 04/07/2004] [Indexed: 10/26/2022]
Abstract
Two modified Ludzack-Ettinger (MLE)-type membrane-coupled bioreactors (MBRs) were investigated in this study for the purpose of removing both nitrogenous and carbonaceous pollutants from a synthetic wastewater. During the first MBR experiment, removal efficiencies were high (>90%) for chemical oxygen demand (COD) and ammonia, but total nitrogenous pollutant removal efficiency was poor (approximately 25%). Bacterial community analysis of ammonia oxidizing bacteria (AOB) by a nested PCR-DGGE approach detected two Nitrosomonas-like populations and one Nitrosospira-like population. During the initial portion of the second MBR experiment, COD and ammonia removal efficiencies were similar to the first MBR experiment until the COD of the influent wastewater was increased to provide additional electron donors to support denitrification. Total nitrogen removal efficiencies eventually exceeded 90%, with a hydraulic residence time (HRT) of 24 h and a recirculation ratio of 8. When the HRT of the MBR experiment was decreased to 12 h, however, ammonia removal efficiency was adversely affected. A subsequent increase in the HRT to 18 h helped improve removal efficiencies for both ammonia (>85%) and total nitrogenous compounds (approximately 70%). Our research demonstrates that MBRs can be effectively designed to remove both carbonaceous and nitrogenous pollutants. The ability of the microbial community to switch between anoxic (denitrifying) and oxic (nitrifying) conditions, however, represents a critical process constraint for the application of MLE-type MBR systems, such that little benefit is gained compared to conventional designs.
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Affiliation(s)
- Sudeshna Ghosh
- Department of Civil Engineering, University of Minnesota, 500 Pillsbury Drive SE, 122 CivE, Minneapolis, MN 55455, USA
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McRae BM, LaPara TM, Hozalski RM. Biodegradation of haloacetic acids by bacterial enrichment cultures. Chemosphere 2004; 55:915-925. [PMID: 15041296 DOI: 10.1016/j.chemosphere.2003.11.048] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2003] [Revised: 08/28/2003] [Accepted: 11/03/2003] [Indexed: 05/24/2023]
Abstract
Haloacetic acids (HAAs) are toxic organic chemicals that are frequently detected in surface waters and in drinking water distribution systems. The aerobic biodegradation of HAAs was investigated in serum bottles containing a single HAA and inoculated with washed microorganisms obtained from enrichment cultures maintained on either monochloroacetic acid (MCAA) or trichloroacetic acid (TCAA) as the sole carbon and energy source. Biodegradation was observed for each of the HAAs tested at concentrations similar to those found in surface waters and in drinking water distribution systems. The MCAA culture was able to degrade both MCAA and monobromoacetic acid (MBAA) with pseudo-first order rate constants of 1.06 x 10(-2) and 1.13 x 10(-2) l(mg protein)(-1) d(-1), respectively, for concentrations ranging from 10(-5) to 2 mM. The pseudo-first order rate constant for TCAA degradation by the TCAA culture was 6.52 x 10(-3) l(mg protein)(-1) d(-1) for concentrations ranging from 5.33 x 10(-5) to 0.72 mM. The TCAA culture was also able to degrade MCAA with the rate accelerating as incubation time increased. Experiments with radiolabeled HAAs indicated that the 14C was primarily converted to 14CO2 with minor incorporation into cell biomass. The community structure of the enrichment cultures was analyzed by both cultivation-dependent and cultivation-independent approaches. Denaturing gradient gel electrophoresis (DGGE) of the PCR-amplified 16S rRNA gene fragments showed that each of the two enrichment cultures had multiple bacterial populations, none of which corresponded to HAA-degrading bacteria cultivated on HAA-supplemented agar plates. This research indicates that biodegradation is a potential loss mechanism for HAAs in surface waters and in drinking water distribution systems.
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Affiliation(s)
- Bethany M McRae
- Department of Civil Engineering, University of Minnesota, 122 Civil Engineering Building, 500 Pillsbury Drive SE, Minneapolis, MN 55455, USA
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Abstract
Membrane-coupled bioreactors (MBRs) offer many benefits compared to conventional biological wastewater treatment systems; however, their performance characteristics are poorly understood. Laboratory-scale MBRs were used to study bacterial adaptations in physiology and community structure. MBRs were fed a mixture of starch, gelatin, and polyoxyethylene-sorbitan monooleate to simulate the polysaccharide, protein, and lipid components of municipal wastewater. Physiological adaptations were detected by measuring ectoenzyme activity while structural dynamics were studied by denaturing gradient gel electrophoresis of PCR-amplified 16S rRNA gene fragments. As cell biomass accumulated in the MBRs, pollutant removal efficiency initially improved and then stabilized with respect to effluent concentrations of chemical oxygen demand, protein, and carbohydrate. Comparison of the MBR effluent to filtered reactor fluid indicated that a portion of the observed pollutant removal was due to filtration by the membrane rather than microbial activity. The rates of ectoenzyme-mediated polysaccharide (alpha-glucosidase) and protein (leucine aminopeptidase) hydrolysis became relatively constant once pollutant removal efficiency stabilized. However, the maximum rate of lipid hydrolysis (heptanoate esterase) concomitantly increased more than 10-fold. Similarly, alpha-glucosidase and leucine aminopeptidase ectoenzyme affinities were relatively constant, while the heptanoate esterase affinity increased more than 30-fold. Community analysis revealed that a substantial community shift occurred within the first 7 days of operation. A Flavobacterium-like bacterial population dominated the community (>50% of total band intensity) and continued to do so for the remainder of the experiment.
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Affiliation(s)
- Christian G Klatt
- University of Minnesota, Department of Civil Engineering, 500 Pillsbury Drive SE, Minneapolis, Minnesota 55455, USA
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Abstract
In this study we analyzed the numbers and types of cultivable tylosin-resistant bacteria from six agricultural soils that differed with respect to their association with subtherapeutic antibiotic use. The proportion of tylosin-resistant bacteria to the total number of bacteria cultivated was significantly higher (7.2-16.5%) at three sites affected by subtherapeutic antibiotic use compared to three sites unaffected by subtherapeutic antibiotic use (0.7-2.5%). We also detected differences in the types of cultivable tylosin-resistant bacteria. At a site affected by subtherapeutic antibiotic use, we detected tylosin-resistant bacteria from the alpha- and beta-subdivisions of Proteobacteria. In contrast, at a site unaffected by subtherapeutic use, we detected only Streptomyces-like (high-G+C Gram-positive) tylosin-resistant bacteria. Our results suggest a link between subtherapeutic use of antibiotics and the numbers and types of antibiotic-resistant bacteria in nearby soil. However, other factors, such as soil type and temporal variation, may have also contributed to the differences observed.
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Affiliation(s)
- Leslie J Onan
- Department of Civil Engineering, University of Minnesota, 500 Pillsbury Drive SE, Minneapolis, MN 55455, USA
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LaPara TM, Zakharova T, Nakatsu CH, Konopka A. Functional and structural adaptations of bacterial communities growing on particulate substrates under stringent nutrient limitation. Microb Ecol 2002; 44:317-326. [PMID: 12399897 DOI: 10.1007/s00248-002-1046-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2002] [Accepted: 09/17/2002] [Indexed: 05/24/2023]
Abstract
Biomass recycle reactors (BRRs) were used as a model system to study the functional and structural adaptations of mixed bacterial communities in response to the imposition of increasingly severe nutrient limitation. BRRs were fed synthetic media containing either spinach homogenate or autoclaved yeast cells to simulate the complex mixtures of particulate carbon sources that are often present in nature. In the BRRs fed spinach homogenate, the biomass (measured as particulate protein) exhibited a physiological response similar to previous studies as detected by 40-80% reductions in respiratory potential and by relatively stable catabolic ectoenzyme activities. Concomitant adaptations in bacterial community structure were detected by PCR-DGGE and RT-PCR-DGGE of 16S rDNA and 16S rRNA fragments, respectively. The microbial community structure was dynamic even after the biomass had reached a quasi-steady state with respect to physiological measurements. In the BRRs fed yeast cells, respiratory potentials increased 2- to 5-fold during the initial portion of the BRR run and alpha-glucosidase and beta-glucosidase activities increased 2- to 4-fold. Substantial bacterial community shifts were also detected in both the rDNA and rRNA profiles, indicating that this community was also structurally dynamic. These experiments suggest that phylogenetically different bacteria sustained the functional activities in these ecosystems in response to increasingly stringent nutrient limitation.
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Affiliation(s)
- T M LaPara
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
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LaPara TM, Nakatsu CH, Pantea LM, Alleman JE. Stability of the bacterial communities supported by a seven-stage biological process treating pharmaceutical wastewater as revealed by PCR-DGGE. Water Res 2002; 36:638-646. [PMID: 11827326 DOI: 10.1016/s0043-1354(01)00277-9] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The stabilities of the bacterial community structures supported by seven full-scale biological reactors treating pharmaceutical wastewater were investigated by denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR) amplified 16S rRNA gene fragments. Effluent quality from this treatment process was consistently high with respect to BOD5 (<30 mgl(-1)), soluble COD (<500 mgl(-1)), and total ammonia (< 5 mgl(-1) as N) concentrations. Long-term community structure stability was studied by comparing the similarity of PCR-DGGE fingerprints from samples collected 87 days apart between which the influent wastewater characteristics were relatively stable. The Dice index (Cs) of similarity was moderately high for the first four reactors (Cs = 0.61-0.77) and very high for the last three reactors (Cs = 0.89-0.91). Short-term community structure stability was studied by comparing PCR-DGGE fingerprints from samples collected 15 days apart between which the influent wastewater characteristics changed significantly, while the effluent quality remained consistently high. The bacterial community composition of each of the seven bioreactors showed a moderate community shift (Cs = 0.70-0.76). Short-term variability in influent wastewater composition, therefore, affected a greater community shift than did long-term operation treating a wastewater of relatively consistent composition. These results indicate that functionally stable wastewater treatment bioreactors have stable microbial community structures under normal operating conditions but are able to adapt in response to perturbations to sustain high effluent quality.
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Affiliation(s)
- Timothy M LaPara
- School of Civil Engineering, Purdue University, West Lafayette, IN 47907-1284, USA.
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