Biofilms in Full-Scale Drinking Water Ozone Contactors Contribute Viable Bacteria to Ozonated Water

Abstract

Concentrations of viable microbial cells were monitored using culture-based and culture-independent methods across multichamber ozone contactors in a full-scale drinking water treatment plant. Membrane-intact and culturable cell concentrations in ozone contactor effluents ranged from 1200 to 3750 cells/mL and from 200 to 3850 colony forming units/mL, respectively. Viable cell concentrations decreased significantly in the first ozone contact chamber, but rose, even as ozone exposure increased, in subsequent chambers. Our results implicate microbial detachment from biofilms on contactor surfaces, and from biomass present within lime softening sediments in a hydraulic dead zone, as a possible reason for increasing cell concentrations in water samples from sequential ozone chambers. Biofilm community structures on baffle walls upstream and downstream from the dead zone were significantly different from each other ( p = 0.017). The biofilms downstream of the dead zone contained a significantly ( p = 0.036) higher relative abundance of bacteria of the genera Mycobacterium and Legionella than the upstream biofilms. These results have important implications as the effluent from ozone contactors is often treated further in biologically active filters and bacteria in ozonated water continuously seed filter microbial communities.

RETRACTED ARTICLE: Metagenomics for taxonomy profiling: tools and approaches

“…In WWTPs, microbes in raw sewage system [106] and trickling filters [105][106][107] were recorded to have an effect on the populations of downstream-activated sludge. The activated sludge biomass [108] also serves as an immigration source for the downstream anaerobic digester [109][110][111]. The effluent [112] from the WWTP will influence the water supply network [113], thus raising the number of microbes and antibiotic-resistant genes associated with the human gut [114].…”

Removal Efficacy of Opportunistic Pathogens and Bacterial Community Dynamics in Two Drinking Water Treatment Trains

“…However, a substantial amount of 16S rRNA genes was retained after ozonation in the present DTWPs (Figure ), in contrast to complete removal of cells in the Swiss study . The difference might be explained by the dominance of membrane‐compromised cells, and/or incomplete inactivation of bacteria cells in some areas of ozonation units (e.g., dead zone), given ozone dosages, water qualities, and specific sampling locations in these two studies were different. Besides, some bacteria are more resistant to ozone than others, which might be able to persist (e.g., mycobacteria, Figure c) and/or enriched during ozonation (e.g., OTUs representing Acidovorax , Methylosinus , and Mycobacterium (Table S3, Supporting Information)).…”

Retrospective Analysis of Nontuberculous Mycobacterial Infection and Monochloramine Disinfection of Municipal Drinking Water in Michigan

“…NTM infections are acquired primarily from waterborne sources, including municipally treated drinking water (2 – 4). NTM have been detected throughout drinking water treatment systems, including in natural water bodies used as sources for drinking water production (5), at treatment plants (5, 6), and in water distribution systems and potable water taps (5, 7, 8).…”