Comparison of the microbiomes of two drinking water distribution systems-with and without residual chloramine disinfection

Michael B Waak; Raymond M Hozalski; Cynthia Hallé; Timothy M LaPara

doi:10.1186/s40168-019-0707-5

Comparison of the microbiomes of two drinking water distribution systems-with and without residual chloramine disinfection

Microbiome. 2019 Jun 7;7(1):87. doi: 10.1186/s40168-019-0707-5.

Authors

Michael B Waak^{1

2}, Raymond M Hozalski^{1

3}, Cynthia Hallé², Timothy M LaPara^{4

5}

Affiliations

¹ Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr SE, Minneapolis, 55455, MN, USA.
² Department of Civil and Environmental Engineering, Norwegian University of Science and Technology, S. P. Andersens veg 5, Trondheim, 7491, Norway.
³ BioTechnology Institute, University of Minnesota, 1479 Gortner Ave, Saint Paul, 55108, MN, USA.
⁴ Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr SE, Minneapolis, 55455, MN, USA. lapar001@umn.edu.
⁵ BioTechnology Institute, University of Minnesota, 1479 Gortner Ave, Saint Paul, 55108, MN, USA. lapar001@umn.edu.

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.

Keywords: 16S rRNA gene amplicon sequencing; Biofilm bacteria; Drinking water distribution systems; Residual chloramine disinfection.

Publication types

Comparative Study
Research Support, Non-U.S. Gov't

MeSH terms

Bacteria / drug effects
Bacteria / genetics
Biofilms / drug effects
Chloramines / pharmacology*
Disinfection*
Drinking Water / chemistry*
Drinking Water / microbiology*
Microbiota*
RNA, Ribosomal, 16S / genetics
Water Microbiology*
Water Purification
Water Supply

Substances

Chloramines
Drinking Water
RNA, Ribosomal, 16S