| 1. |
- Chan, Sandy, et al.
(författare)
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Bacterial release from pipe biofilm in a full-scale drinking water distribution system
- 2019
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Ingår i: npj Biofilms and Microbiomes. - : Springer Science and Business Media LLC. - 2055-5008. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- Safe drinking water is delivered to the consumer through kilometres of pipes. These pipes are lined with biofilm, which is thought to affect water quality by releasing bacteria into the drinking water. This study describes the number of cells released from this biofilm, their cellular characteristics, and their identity as they shaped a drinking water microbiome. Installation of ultrafiltration (UF) at full scale in Varberg, Sweden reduced the total cell count to 1.5 × 10 3 ± 0.5 × 10 3 cells mL −1 in water leaving the treatment plant. This removed a limitation of both flow cytometry and 16S rRNA amplicon sequencing, which have difficulties in resolving small changes against a high background cell count. Following installation, 58% of the bacteria in the distributed water originated from the pipe biofilm, in contrast to before, when 99.5% of the cells originated from the treatment plant, showing that UF shifts the origin of the drinking water microbiome. The number of bacteria released from the biofilm into the distributed water was 2.1 × 10 3 ± 1.3 × 10 3 cells mL −1 and the percentage of HNA (high nucleic acid) content bacteria and intact cells increased as it moved through the distribution system. DESeq2 analysis of 16S rRNA amplicon reads showed increases in 29 operational taxonomic units (OTUs), including genera identified as Sphingomonas, Nitrospira, Mycobacterium, and Hyphomicrobium. This study demonstrated that, due to the installation of UF, the bacteria entering a drinking water microbiome from a pipe biofilm could be both quantitated and described.
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| 2. |
- Chan, Sandy, et al.
(författare)
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Monitoring biofilm function in new and matured full-scale slow sand filters using flow cytometric histogram image comparison (CHIC)
- 2018
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354. ; 138, s. 27-36
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Tidskriftsartikel (refereegranskat)abstract
- While slow sand filters (SSFs) have produced drinking water for more than a hundred years, understanding of their associated microbial communities is limited. In this study, bacteria in influent and effluent water from full-scale SSFs were explored using flow cytometry (FCM) with cytometric histogram image comparison (CHIC) analysis; and routine microbial counts for heterotrophs, total coliforms and Escherichia coli. To assess if FCM can monitor biofilm function, SSFs differing in age and sand composition were compared. FCM profiles from two established filters were indistinguishable. To examine biofilm in the deep sand bed, SSFs were monitored during a scraping event, when the top layer of sand and the schmutzdecke are removed to restore flow through the filter. The performance of an established SSF was stable: total organic carbon (TOC), pH, numbers of heterotrophs, coliforms, E. coli, and FCM bacterial profile were unaffected by scraping. However, the performance of two newly-built SSFs containing new and mixed sand was compromised: breakthrough of both microbial indicators and TOC occurred following scraping. The compromised performance of the new SSFs was reflected in distinct effluent bacterial communities; and, the presence of microbial indicators correlated to influent bacterial communities. This demonstrated that FCM can monitor SSF performance. Removal of the top layer of sand did not alter the effluent water from the established SSF, but did affect that of the SSFs containing new sand. This suggests that the impact of the surface biofilm on effluent water is greater when the deep sand bed biofilm is not established.
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| 3. |
- Paul, Catherine J., et al.
(författare)
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Assessment of the mobile biofilm microbiome in distributed drinking water following installation of hybrid ultrafiltration process, in Varberg, Sweden.
- 2018
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Konferensbidrag (refereegranskat)abstract
- Drinking water is delivered from the treatment plant to the consumer through kilometres of pipes. Lining these pipes are communities of bacteria living as biofilms. Little is known about the microbial ecology of these biofilms, as access to drinking water pipes for sampling is often limited to pipes sporadically removed for repair or replacement. Bacteria are constantly exchanged between the biofilm and flowing water, however with bacteria in the water leaving the treatment plant reaching numbers as high as 700 000 cells per millilitre, identifying those cells originating from the biofilm is difficult.Membrane hybrid processes—coagulation coupled with ultrafiltration (UF)—have become a common method to comply with the legal, chemical, and microbiological requirements for drinking water. The main advantages of integrating coagulation with membrane filtration are the enhanced removal of natural organic matter (NOM) and reduced membrane fouling. Therefore, in November 2016, the Kvarnagården WTP in Varberg, Sweden was upgraded with a UF facility (capacity of 1080 m3 h−1 net permeate flow rate). The commissioning of the UF treatment process at Kvarnagården WTP, provided the opportunity to observe the microbial consequences of exposing a distribution system previously exposed to high cellular counts, to a virtually cell-free water phase. By observing which bacteria entered this new water phase, particularly those appearing after an extended time within the distribution system, a snapshot would be obtained of which bacteria can enter the water phase from the pipe biofilm.Water samples were taken before, three days after, and for one month after, installation of UF for flow cytometry (FCM) and Illumina 16S rRNA gene sequencing. FCM gives total cell counts and some additional parameters (%intact cells, %HNA) to describe the bacterial community, while DNA sequencing provides detailed genetic descriptions. Samples from the UF feed showed an average of 8 x105 cells/mL while filtered water contained 2.4 x 104 cells/mL. FCM also showed that UF removed intact cells, but that filtration by this method did not show a preference for either high (HNA) or low (LNA) nucleic acid-containing bacteria. Water samples from three locations at increasing distance from the treatment plant were taken within the distribution system. These samples showed an increase in total cells, with, on average, an addition of 0.6 x 104 cells/ mL, contributed from bacteria leaving the biofilm. These bacteria from the biofilm were further characterized by FCM as intact cells containing an increased percentage of HNA cells, relative to the water leaving the treatment plant. DNA sequencing of all samples, followed by the bioinformatics pipeline QIIME, further revealed the community present in the filtered water originating from the biofilm. Community content in the distributed water was distinct from the finished water, and also differed with respect to location within the distribution system. Both species richness and diversity in the distributed water decreased following installation of UF, as measured by Chao´s richness and Shannon diversity index. Differential analysis of the sequencing reads counts by DESeq2 were used to detect statistical significant operational taxonomic units (OTUs) that have changed over the travel across the pipes. Several groups of bacteria were identified associated with filtered water that had, and had not been, in contact with biofilm. These included Hyphomicrobium, Pedomicrobium, Nitrospira, Sphingomonas, Mycobacterium and Rhodobacter as well as several unidentified genera. This suggests that these are the most mobile members of the pipe biofilms in this distribution system. How the mobility of these groups change over seasons or how the overall microbiome of both the biofilm and the water phase in this distribution system will adapt to the filtered water over a longer time period will provide additional information about how pipe biofilms respond to large changes in the microbiology of distributed water.
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| 4. |
- Paul, Catherine J., et al.
(författare)
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Disturbance of the bacterial communities in drinking water produced from established and newly-built slow sand filters
- 2016
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Konferensbidrag (refereegranskat)abstract
- IntroductionSlow sand filtration is an established method for drinking water treatment, however, the knowledge about their microbial ecology remains limited. Maintenance of slow sand filters (SSF) includes washing to remove biofilm growth in the sand and restore flow through the filter. Understanding how this impacts produced water is important as the SSF may influence the bacterial flora in the finished drinking water and distribution system biofilms (El-Chakhtoura et al. 2015, Lührig et al. 2016, manuscript in preparation). Routine SSF monitoring after washing includes heterotrophic plate count (HPC) however this only describes a small fraction of the bacteria in the water (Allen, Edberg et al. 2004). Flow cytometry (FC) has been proposed for routine monitoring of bacteria in drinking water. FC counts the cells present in water and generates a fingerprint based on describing differential DNA staining to describe the population of bacteria (Arnoldini et al. 2013). Two full-scale new SSFs were constructed using different types of sand as starting material. Traditional microbial parameters (HPC, coliforms and E. coli) and FC data suggested these SSFs differed from each other and were not performing as well as established SSFs (Chan et al. 2016, manuscript in preparation). This study explored: using FC for routine monitoring of SSFs during washing; and, if the response to washing differed between each of the newly built SSFs when compared to an established SSF. Materials and MethodsInfluent and effluent water were characterized using HPC, the Colilert method (E.coli and coliforms), and FC according to established protocols (Prest et al. 2013). FC data was analyzed with Cytometric Histogram Image Comparison (CHIC) (Koch et al. 2013). Results and ConclusionsTwo new SSFs were built using only new sand (SSF-new), or a mix of new sand with sand previously removed during washing from existing sand filters (SSF-mix). After 6 months, the impact on water quality of disturbance from SSF washing was determined by comparing the bacterial populations of the influent and effluent water from SSF-new, SSF-mix, and an established SSF (SSF-est). No significant log reduction of cells was observed in any effluent water. The fluorescence distribution of effluent differed from that of the influent with each SSF showing a unique fingerprint (Fig 1.1). Figure 1.1 Comparison of fluorescence fingerprints for (left to right) SSF-est, SSF-mix, and SSF-new. Profiles show the combined plot of cell concentration and fluorescence distribution of nucleic acid stained with SYBR Green I in effluent water before wash (blue), and 4 days after washing (red).Fingerprints of effluent water were stable throughout the sampling period for SSF-est, regardless of washing, while for SSF-new and SSF-mix, fingerprints suggested a destabilization of the bacterial population related to washing. This suggested that SSF-new, SSF-mix and SSF-est differed in the population of cells being seeded into their respective effluent waters and this was supported by results from traditional methods and qPCR, showing lowest number of coliforms in the effluent from SSF-est. Analysis by CHIC, showed that the cell populations seeded by SSF-mix were more similar to those from SSF-est, than SSF-new. FC fingerprints from SSF-new were very similar to those of the influent water, suggesting that the biofilm in this SSF had little impact on the water passing through SSF-new. Since SSF-mix included washed sand from established SSFs, this appears to have inoculated the SSF-mix biofilm in a way that was not observed for SSF-new. The fingerprints for SSF-est effluent remained stable, consistent with a biofilm that is resilient to disturbance, and coliform counts demonstrating uninterrupted SSF function. This study thus suggests that washed sand is preferable to new sand for SSF construction and that more than 6 months is required for a resilient SSF biofilm. While total cell numbers did not change significantly across any SSF, SSF-est selectively reduced HPC and coliforms suggesting that this biofilm function is selective compared to newer SSF biofilms. In this study FC was not only useful for monitoring total cell counts to follow changes during SSF washing, but showed a consistent effluent water fingerprint associated with a resilient and functional SSF biofilm. As this was not observed for the newly built SSFs, FC can follow both the character and establishment of SSF biofilms and should be helpful for analyzing the impacts of any potential events on SSF biofilm integrity.ReferencesAllen, M.J., Edberg, S.C. and Reasoner, D.J., (2004). Heterotrophic plate count bacteria—what is their significance in drinking water? International journal of food microbiology, 92(3), pp.265-274.Arnoldini, M., Heck, T., Blanco-Fernández, A. and Hammes, F., (2013). Monitoring of dynamic microbiological processes using real-time flow cytometry. PloS one, 8(11), p.e80117.El-Chakhtoura, J., Prest, E., Saikaly, P., van Loosdrecht, M., Hammes, F. and Vrouwenvelder, H., 2015. Dynamics of bacterial communities before and after distribution in a full-scale drinking water network. Water Research, 74, pp.180-190.Koch, C., Fetzer, I., Harms, H. and Müller, S., (2013). CHIC—an automated approach for the detection of dynamic variations in complex microbial communities. Cytometry Part A, 83(6), pp.561-567.Prest, E.I., Hammes, F., Kötzsch, S., Van Loosdrecht, M.C.M. and Vrouwenvelder, J.S., (2013). Monitoring microbiological changes in drinking water systems using a fast and reproducible flow cytometric method. Water research, 47(19), pp.7131-7142.
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| 5. |
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| 6. |
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| 7. |
- Pullerits, Kristjan, et al.
(författare)
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Impact of coagulation–ultrafiltration on long-term pipe biofilm dynamics in a full-scale chloraminated drinking water distribution system
- 2020
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Ingår i: Environmental Science: Water Research & Technology. - 2053-1419. ; 6:11, s. 3044-3056
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Tidskriftsartikel (refereegranskat)abstract
- While pipe biofilms in DWDSs (drinking water distribution systems) are thought to affect the quality of distributed water, studies regarding the microbial processes are impeded by the difficulties in accessing biofilm undisturbed by DWDS maintenance. In this study, pipe sections were removed from a fully operational DWDS for biofilm sampling over two years and three months, and before and after start of ultrafiltration (UF) with coagulation treatment in the drinking water treatment plant (DWTP). Water (n = 31), surface biofilm (obtained by swabbing, n = 34) and deep pipe biofilm (obtained by scraping, n = 34) were analyzed with 16S rRNA gene amplicon sequencing; with flow cytometry, and chemical and natural organic matter (NOM) analysis as additional parameters for water quality. UF with coagulation decreased the total cell concentration in the DWDS bulk water from 6.0 × 105 ± 2.3 × 105 cells per ml to 6.0 × 103 ± 8.3 × 103 cells per ml, including fluctuations due to seasonal change, as well as decreasing most analyzed fractions of NOM. UF treatment of the water revealed that 75% ± 18% of the cells in the water originated from DWDS biofilm, confirmed by SourceTracker analysis, with the rest of the cells likely released from biofilm on DWTP storage tanks. Following UF start, the ASVs (amplicon sequence variants) in the deep pipe biofilm decreased, and Evenness and Shannon diversity indices decreased, reflecting the community's response to the new environment created by the altered water quality. The pipe biofilm community was dominated by ASVs classified as Nitrosomonadaceae, Nitrospira, Hyphomicrobium and Sphingomonas, with relative abundances ranging from 5–78%, and also included ASVs of genus Mycobacterium, genus Legionella and order Legionellales. This community composition, together with the observation that turnover of nitrogen compounds was unchanged by UF start, indicate that nitrification in the DWDS was localized to the pipe biofilm.
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| 8. |
- Pullerits, Kristjan
(författare)
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Impact of Drinking Water Treatment and Pipe Biofilms on Bacterial Dynamics in the Distribution System
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis addresses drinking water quality and microbiology in full-scale drinking water distribution systems (DWDSs). It examines how UV irradiation and slow sand filters (SSFs) alter the water bacteriome, and how the biofilm in the DWDS affects the drinking water quality.In addition, the effects of installing a combined ultrafiltration and coagulation treatment stage on the pipe biofilm community in a DWDS were assessed.PCR-based methods were assessed and developed to be able to monitor the effects of UV irradiation. The impact of UV doses of 250, 400, and 600 J/m2, delivered to water at a full-scale drinking water treatment plant (DWTP), was investigated using 16S rRNA gene amplicon sequencing. Phylogenetic analysis, including differential abundance analysis using DESeq2, showed that Actinobacteria were more resistant to UV irradiation, whereas Bacteroidetes were sensitive to UV irradiation. Amplicon sequence variants (ASVs) resistant to UV had a greater average guanine-cytosine(GC) content than ASVs sensitive to UV irradiation: 55% ± 1.7 (n = 19) vs. 49% ± 2.5 (n = 16), respectively. UV irradiation may affect the microbial dynamics and the biostability throughout the DWDS, as the composition of a bacterial community in irradiated water stored for 6 days at 7 °C to approximate conditions in the DWDS, changed compared to the non-irradiated controls.Full-scale SSFs were studied using flow cytometry (FCM) and cytometric histogram image comparison (CHIC) analysis. An established, well-functioning SSF removed coliforms and Escherichia coli, and reduced the pH and the amount of total organic carbon, even when the schmutzdecke of the SSFs was removed. This was in contrast to two new filters, which showed compromised performance, including breakthrough of coliforms and E. coli. FCM analysis showed that well-functioning SSFs changed the microbial community of the influent water to include more low nucleic acid (LNA) bacteria in the filter effluent. The SSF with a mixture of new sand plus sand from established SSFs on top exhibited better performance than a SSF with new sand, indicating that priming with sand from established SSFs may be favorable when constructing new SSFs. Monitoring the SSFs with FCM and CHIC analysis was demonstrated to be a fast, reliable and informative method of monitoring the bacterial community in water.An ultrafiltration and coagulation step was installed at a DWTP (hereafter defined as UF start). This removed almost all the bacteria from the finished water, and reduced the total cell concentration (TCC) in the distributed water from 6.0 × 105 (± 2.3 × 105) cells/mL to 6.0 × 103 (± 8.3 × 103) cells/mL, taking seasonal variations into account. After the UF start, almost all the bacteria in the drinking water leaving the DWDS originated from the pipe biofilm, although no significant biofilm detachment was observed. The removal of cells by UF allowed the identification of the bacteria released from the mature pipe biofilm, which included Sphingomonas, Nitrospira, Mycobacterium, and Hyphomicrobium. The biofilms of excavated pipe sections were analyzed over a period of 27 months in order to study how the biofilm adapted to the new UF water quality. It was observed that the bacterial community was dominated by Nitrosomonadaceae, Nitrospira, Hyphomicrobium and Sphingomonas, confirming the previous results. DNA sequences classified as belonging to the opportunistic pathogens Mycobacterium and Legionella were also detected in the pipe biofilms. The high relative abundance of the nitrifying bacteria Nitrosomonadaceae and Nitrospira, together with the fact that the turnover of nitrogen compounds was unchanged by UF start indicated that nitrification in the DWDS was localized to the pipe biofilm. The bacterial community on the pipes changed following UF start and a stable community was reached after 18 months, while still maintaining the turnover of nitrogen compounds. The bacteria leaving the biofilm after a shorter residence time (<25 h) were high nucleic acid (HNA) bacteria, and a shift to an increased relative abundance of LNA bacteria was observed with longer residence times of up to about 170 h.
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| 9. |
- Pullerits, Kristjan, et al.
(författare)
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Impact of UV irradiation at full scale on bacterial communities in drinking water
- 2020
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Ingår i: npj Clean Water. - : Springer Science and Business Media LLC. - 2059-7037. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Water in a full-scale drinking water treatment plant was irradiated with ultraviolet (UV) doses of 250, 400, and 600 J/m2, and the effect on bacterial communities investigated using 16s rRNA gene amplicon sequencing, heterotrophic plate counts (HPCs), coliform, and Escherichia coli counts. The bacteria in the irradiated water were also analyzed following storage for 6 days at 7 °C, to approximate the conditions in the distribution system. The log10 reduction of HPCs at 400 J/m2 was 0.43 ± 0.12. Phylogenetic examination, including DESeq2 analysis, showed that Actinobacteria was more resistant to UV irradiation, whereas Bacteroidetes was sensitive to UV. Phylum Proteobacteria contained monophyletic groups that were either sensitive or resistant to UV exposure. The amplicon sequence variants (ASVs) resistant to UV irradiation had a greater average GC content than the ASVs sensitive to UV, at 55% ± 1.7 (n = 19) and 49% ± 2.5 (n = 16), respectively. Families Chitinophagaceae, Pelagibacteraceae, Holophagaceae, Methylophilaceae, and Cytophagaceae decreased linearly in relative abundance, with increasing UV dose (P < 0.05, Pearson’s correlation). When irradiated water was stored, Chitinophagaceae, Comamonadaceae, and Flavobacteriaceae families decreased in relative abundance, whereas ACK-M1, Mycobacteriaceae, and Nitrosomonadaceae were increasing in relative abundance. This suggests that the impact of UV irradiation cannot only be considered directly after application but that this treatment step likely continues to influence microbial dynamics throughout the distribution system.
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| 10. |
- Rosenqvist, Tage, et al.
(författare)
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Succession of bacterial biofilm communities following removal of chloramine from a full-scale drinking water distribution system
- 2023
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Ingår i: npj Clean Water. - 2059-7037. ; 2023:6
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Tidskriftsartikel (refereegranskat)abstract
- Monochloramine is used to regulate microbial regrowth in drinking water distribution systems (DWDS) but produces carcinogenic disinfection byproducts and constitutes a source of energy for nitrifying bacteria. This study followed biofilm-dispersed microbial communities of a full-scale DWDS distributing ultrafiltered water over three years, before and after removal of monochloramine. Communities were described using flow cytometry and amplicon sequencing, including full-length 16S rRNA gene sequencing. Removal of monochloramine increased total cell counts by up to 440%. Increased abundance of heterotrophic bacteria was followed by emergence of the predatory bacteria Bdellovibrio, and a community potentially metabolizing small organic compounds replaced the nitrifying core community. No increased abundance of Mycobacterium or Legionella was observed. Co-occurrence analysis identified a network of Nitrosomonas, Nitrospira, Sphingomonas and Hyphomicrobium, suggesting that monochloramine supported this biofilm community. While some species expanded into the changed niche, no immediate biological risk to consumers was indicated within the DWDS.
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| 11. |
- Schleich, Caroline, et al.
(författare)
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Mapping Dynamics of Bacterial Communities in a Full-Scale Drinking Water Distribution System Using Flow Cytometry
- 2019
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Ingår i: Water. - : MDPI AG. - 2073-4441. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Microbial monitoring of drinking water is required to guarantee high quality water and to mitigate health hazards. Flow cytometry (FCM) is a fast and robust method that determines bacterial concentrations in liquids. In this study, FCM was applied to monitor the dynamics of the bacterial communities over one year in a full-scale drinking water distribution system (DWDS), following implementation of ultrafiltration (UF) combined with coagulation at the drinking water treatment plant (DWTP). Correlations between the environmental conditions in the DWDS and microbial regrowth were observed, including increases in total cell counts with increasing retention time (correlation coefficient R = 0.89) and increasing water temperature (up to 5.24-fold increase in cell counts during summer). Temporal and spatial biofilm dynamics affecting the water within the DWDS were also observed, such as changes in the percentage of high nucleic acid bacteria with increasing retention time (correlation coefficient R = −0.79). FCM baselines were defined for specific areas in the DWDS to support future management strategies in this DWDS, including a gradual reduction of chloramine.
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