Long-term influences of pipe materials on bacterial communities of matured biofilms (\> 40 years' old) in drinking water distribution systems

Our plain-English summary of Long-term influences of pipe materials on bacterial communities of matured biofilms (> 40 years' old) in drinking water distribution systems, by A. Ren, J. Li, Z. Zhang, et al (Fundamental Research, 2026).

The study

• Authors: A. Ren, J. Li, Z. Zhang, E. van der Mark, L. Chen, X. Li, W. van der Meer, G. Liu
• Journal: Fundamental Research
• Published: 2026;6(4):2369-2375
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Pipe materials appear to play an important role in the development of biofilms in drinking water distribution systems. However, there is controversy as to whether pipe materials shape the composition and diversity of bacterial communities in biofilms. To investigate the long-term effects of pipe materials on biofilms, triplicate samples of mature biofilms on unplasticized polyvinyl chloride (PVC-U), grey cast iron and asbestos cement (pipe age > 40 years) were obtained from three areas of an unchlorinated drinking water distribution system in the Netherlands. Illumina sequencing was performed and 773 OTUs (730 OTUs-814 OTUs) were detected within the biofilms on the three pipe materials, all of which were dominated by Proteobacteria (36.2%-46.1%). Both the alpha and beta diversity results showed that the bacterial communities of the biofilms formed on different pipe materials were highly similar. The neutral community model revealed that the assembly of the biofilm communities was governed by environmental selection rather than neutral processes. Among the 142 shared OTUs between the water and biofilm samples, there were 25 enriched OTUs (e.g., OTU7, assigned as Nitrospira spp.), which accounted for 62.6% of the total sequences, while 16 OTUs were disadvantaged (e.g., OTU14 and OTU40, assigned as Hyphomicrobiaceae), accounting for 2.2% of the sequences. Based on the findings, we propose and discuss a harmonisation process by which biofilms with significant differences due to the pipe material harmonize over time resulting in biofilms with similar bacterial communities. Our findings provide valuable insights into long-term biofilm development, bridging an essential gap in our current understanding of the influence of pipe materials on biofilm communities. These findings also highlight the importance of long-term studies and point to a potentially masked harmonizing process during biofilm development over years/decades.

© 2024 The Authors. Publishing Services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd.

In plain English

This field study compared bacterial biofilms that had grown for decades inside three water mains of different materials in an unchlorinated drinking water system in the Netherlands. The pipes were unplasticized PVC (PVC-U, 42 years old), asbestos cement (58 years old) and grey cast iron (50 years old). The authors took three biofilm samples from each pipe and water samples from the treatment plant and the three sites, then identified bacteria by DNA sequencing. Water samples held on average 1205 bacterial types (OTUs), against an average of 773 in biofilms. Biofilms had 814 OTUs on asbestos cement, 775 on PVC-U and 730 on cast iron. These differences between materials were not statistically significant. Among the dominant bacterial types, two were found in biofilms on the asbestos cement pipe but not on the other two pipes. A modelling analysis indicated that biofilm communities were shaped by environmental selection rather than chance. The authors concluded that biofilms on the three materials were highly similar. They noted that they had few water samples and no historical water samples. The study looked only at bacteria, not at asbestos fibers or human health.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: field sampling study of mature biofilms and water in a full-scale drinking water distribution system, using DNA sequencing
• Who was studied: Biofilms from three 110 mm water mains, aged 42, 58 and 50 years, in three distribution areas supplied by the Katwijk treatment plant of Dunea, the Netherlands. Nine biofilm samples (three per pipe) and four water samples were taken.
• Exposure: Pipe material: unplasticized PVC (PVC-U, laid 1978), asbestos cement (AC, laid 1962) and grey cast iron (GCI, laid 1970). No asbestos fiber type is named, and no human exposure was studied.
• Main results:
  • Water samples averaged 1205 OTUs (n = 4), more than the biofilm samples (773 OTUs on average, n = 9).
  • Biofilms had 814 OTUs on asbestos cement, 775 on PVC-U and 730 on grey cast iron.
  • The differences in OTU numbers among biofilms on the different materials were not statistically significant.
  • Proteobacteria were the leading group in both biofilms (36.2% to 46.1%) and water (15.5% to 25.2%).
  • Among the dominant OTUs in the pipe biofilms, 13 of 17 were shared by all three materials. Two dominant OTUs (OTU10, OTU19) were detected in biofilms on the asbestos cement pipe but not in biofilms on the PVC-U or cast iron pipes.
  • Only 142 OTUs were shared between water and biofilms, 2.4% of observed OTUs.
  • Of the shared OTUs, those selected by the environment (25 enriched OTUs) accounted for 62.6% of shared sequences. The authors took the model results to mean that biofilm assembly was governed by environmental selection rather than neutral processes.
• The authors' conclusion: The authors concluded that mature biofilm communities on PVC-U, asbestos cement and grey cast iron pipes were highly similar, indicating a minor influence of pipe material. They said the long-term effects of pipe material and the proposed harmonizing process require further exploration.
• Limitations the authors state:
  • The number of water samples was low, which the authors say explains the low number of shared OTUs.
  • Historical water samples were not available, and the water samples taken were only snapshots.
  • Bacterial communities varied significantly among the bulk water samples.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Cement.

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• Evidence of arsenic release promoted by disinfection by-products within drinking-water distribution systems — S.S. Andra, K.C. Makris, et al. (2014)
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• Degradation of asbestos - Reinforced water supply cement pipes after a long-term operation — J. Zavašnik, A. Šestan, et al. (2022)
• The use of asbestos-cement pipe for public water supply and the incidence of cancer in selected communities in Utah — T.D. Sadler, W.N. Rom, et al. (1984)

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