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Kim T, Behrens SF, LaPara TM. Different Engineering Designs Have Profoundly Different Impacts on the Microbiome and Nitrifying Bacterial Populations in Municipal Wastewater Treatment Bioreactors. Appl Environ Microbiol 2021; 87:e0104421. [PMID: 34232710 DOI: 10.1128/AEM.01044-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Numerous wastewater treatment processes are designed by engineers to achieve specific treatment goals. However, the impact of these different process designs on bacterial community composition is poorly understood. In this study, 24 different municipal wastewater treatment facilities (37 bioreactors) with various system designs were analyzed by sequencing of PCR-amplified 16S rRNA gene fragments. Although a core microbiome was observed in all of the bioreactors, the overall microbial community composition (analysis of molecular variance; P = 0.001) as well as that of a specific population of Nitrosomonas spp. (P = 0.04) was significantly different between A/O (anaerobic/aerobic) systems and conventional activated sludge (CAS) systems. Community α-diversity (number of observed operational taxonomic units [OTUs] and Shannon diversity index) was also significantly higher in A/O systems than in CAS systems (Wilcoxon; P < 2 × 10-16). In addition, wastewater bioreactors with short mean cell residence time (<2 days) had very low community α-diversity and fewer nitrifying bacteria compared to those of other system designs. Nitrospira spp. (0.71%) and Nitrotoga spp. (0.41%) were the most prominent nitrite-oxidizing bacteria (NOB); because these two genera were rarely prominent at the same time, these populations appeared to be functionally redundant. Weak evidence (AOB:NOB « 2; substantial quantities of Nitrospira sublineage II) was also obtained suggesting that complete ammonia oxidation by a single organism was occurring in system designs known to impose stringent nutrient limitation. This research demonstrates that design decisions made by wastewater treatment engineers significantly affect the microbiome of wastewater treatment bioreactors. IMPORTANCE Municipal wastewater treatment facilities rely on the application of numerous "activated sludge" process designs to achieve site-specific treatment goals. A plethora of microbiome studies on municipal wastewater treatment bioreactors have been performed previously; however, the role of process design on the municipal wastewater treatment microbiome is poorly understood. In fact, wastewater treatment engineers have attempted to control the microbiome of wastewater bioreactors for decades without sufficient empirical evidence to support their design paradigms. Our research demonstrates that engineering decisions with respect to system design have a significant impact on the microbiome of wastewater treatment bioreactors.
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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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