Nitrifying niche differentiation in biofilms from full-scale chloraminated drinking water distribution system

Impact of coagulation–ultrafiltration on long-term pipe biofilm dynamics in a full-scale chloraminated drinking water distribution system

“…8,14 The communities at BF1 and BF4, and those in the water following UF start, decreased in evenness and Shannon diversity with time, indicating selection of bacteria (ASVs) for the new environment, and possibly reflecting the relative increase in monochloramine concentration as lower diversity has been proposed to correlate with higher disinfectant concentration. 13 ASVs capable of oxidizing ammonia (Nitrosomonadaceae 197, BF1) decreased in relative abundance following UF start, however, other Nitrosomonadaceae taxa (196) increased at the same sampling location, reflecting adaptation, and demonstrating functional redundancy for conversion of ammonia to nitrite. Relative abundance of Nitrospira also responded to UF start, with decreases in Nitrospira ASVs 102 103 and 104 at sampling point BF4, and increase in Nitrospira ASV 101, with no change in nitrate concentrations.…”

“…In a study using batch reactors, ammonia concentrations only decreased in the reactor containing particulate matter obtained from filtration of drinking water, while all reactors maintained similar TCC in the bulk water phase, supporting that nitrification may require cells attached to surfaces. 51 Large populations of nitrifiers were identified in tropical chloraminated pipe biofilms, and nitrification activity in biofilm corresponded to identified taxa; 13 and, nitrogen biotransformation in chloraminated DWDS and reservoirs has been linked to diverse populations including nitrifiers and heterotrophic bacteria. 19,52 This suggests that to maintain monochloramine residual, drinking water producers need to consider nitrification occurring in the biofilm and that, regardless of biological content in the distributed water, disinfection concentration will continue to be determined by location within the DWDS.…”

“…11,12 Grab samples of pipe biofilm, obtained for research purposes or during pipe maintenance, have also been investigated. 1,8,[13][14][15] Maintaining disinfectant residuals such as chloramine to repress growth of problematic organisms in the DWDS is common practice. This use is however debatable since resistant microorganisms can be selected 16 and, in combination with organic matter, cause undesirable disinfection byproducts to form.…”

“…18 Bacteria in chloraminated drinking water included a community with diverse approaches to nitrogen metabolism dominated by Nitrosomonas (AOB), and Nitrospira (NOB) and accompanied by heterotrophs such as Sphingomonas 19 and these taxa were recently identified as actively conducting nitrification in diverse pipe biofilms. 13 When a drinking water treatment plant (DWTP) in Varberg, Sweden, installed an ultrafiltration (UF) facility with two-stage filtration and in-line coagulation at the primary membrane stage, 20 the new finished water (FW) contained virtually no bacteria, and less and different natural organic matter (NOM). 11 The impact of this change on the bacterial community was examined by collecting water, swabbing the surface of the biofilm, and scraping to remove deep biofilm from multiple sections of pipe in series and excavated from the operational DWDS.…”

Factors Shaping Young and Mature Bacterial Biofilm Communities in Two Drinking Water Distribution Networks

“…There is an increasing recognition of public health risks in drinking water distribution (DWDS) and premise plumbing systems where water stagnation and decay of residual disinfectant favor regrowth of microorganisms within the pipe networks (Allaire et al 2018, Hull et al 2019, Raskin and Nielsen 2019). Biofilms can act as reservoirs of both enteric and opportunistic pathogens, which may then be released back into the bulk water (Cruz et al 2020, Flemming et al 2016, Flemming and Wuertz 2019). Several outbreaks of illnesses such as legionellosis, which results in high morbidity and mortality in susceptible individuals, have been associated with poor drinking water quality (Ashbolt 2015).…”