Phosphate Dosing in Drinking Water Distribution Systems Promotes Changes in Biofilm Structure and Functional Genetic Diversity

Abstract

Water utilities treat drinking water by adding phosphate to prevent metal dissolution from water pipe work systems and particularly lead poisoning. Phosphate can be a limiting nutrient for microbial biofilms in DWDS, yet its effects on these microbial consortia are not well understood. This research presents results from phosphate dosing experiments using a real scale chlorinated DWDS, comparing standard phosphate concentrations of United Kingdom drinking water (1 mgP/L) with a double dose (2 mgP/L) commonly used in plumbosolvency treatment. Biofilm development during phosphate treatment experiments was monitored using a holistic approach by combining metagenomics analysis, flow cytometry and SEM characterisation. The increase of phosphate levels in drinking water, reduced biofilm cell numbers and promoted the presence of poorly distributed biofilms on inner pipe surfaces. Metagenomics analysis using genetic markers (16S rRNA and ITS2) showed that phosphate influenced biofilm community structure, particularly fungal composition. Whole metagenome sequencing showed that phosphate enrichment favoured the presence of sequencing reads associated to ATPases, ion transporters and DNA-interacting proteins, whilst reads associated to nitrogen metabolism were predominant in control samples. This research brings new knowledge regarding the influence of phosphate treatment on the composition and structure of biofilms within DWDS, and the implications that this might have for the management of these systems.

Implications of Climate Change: How Does Increased Water Temperature Influence Biofilm and Water Quality of Chlorinated Drinking Water Distribution Systems?

“…Each experiment comprised of a biofilm growth phase of 30 days, followed by a flushing programme used to study the mobilisation dynamics of biofilms from pipe surfaces ( Supplementary Table 1 and Supplementary Figure 2 ). The biofilm growth phase of 30 days was selected based on previous studies in the same facility that showed this time as sufficient to detect and monitor discolouration and biofilm mobilisation events, as well as microbial community changes ( Douterelo et al, 2013 , 2014b ; Fish and Boxall, 2018 ; Rosales et al, 2020 ).…”

Effect of microbially available phosphorous removal on Legionella spp. in multi-storey residential dwellings in Latvia

“…Phosphate addition can impact both bacterial and fungal biofilm communities, 22,23 leading to a decrease in bacterial abundance, while supporting the opposite for fungi. 22 This addition may also affect functional traits, 23 potentially inducing a “luxury P-uptake” mechanism. This mechanism could enhance phosphate uptake in microorganisms that were subjected to P-starvation within a MAP-limited system.…”

“…20 Similar to temperature-induced niches, nutrient composition also plays a crucial role in shaping microbial communities. [21][22][23] It affects the production of microbial products like exopolysaccharides (EPS), 21 which, in turn, influence biofilm structure. Phosphate addition can impact both bacterial and fungal biofilm communities, 22,23 leading to a decrease in bacterial abundance, while supporting the opposite for fungi.…”

“…[21][22][23] It affects the production of microbial products like exopolysaccharides (EPS), 21 which, in turn, influence biofilm structure. Phosphate addition can impact both bacterial and fungal biofilm communities, 22,23 leading to a decrease in bacterial abundance, while supporting the opposite for fungi. 22 This addition may also affect functional traits, 23 potentially inducing a "luxury P-uptake" mechanism.…”

Exploring the Impacts of Full-Scale Distribution System Orthophosphate Corrosion Control Implementation on the Microbial Ecology of Hydrologically Connected Urban Streams

“…Given the strong nutrient limitations for organisms in water systems, increased abundance of Cyanobacteria and other eutrophication-related taxa could be a likely observation due to an increase in biologically available phosphate to be used for growth and cell maintenance ( 23 , 24 ) in the urban stream waters. In addition, recent metagenomics studies in the UK drinking water DS found an increase in microorganisms related to enhanced phosphate metabolism (e.g., polyphosphate accumulating taxa such as “ Candidatus Accumulibacter”) ( 13 , 17 , 25 ) after increased phosphate addition. With the aging drinking water infrastructure across the nation that contributes millions of gallons per day in lost treated drinking water (through unmetered buildings and pipe breaks) ( 26 ), it is important to consider the impacts of such additions on urban stream microbiomes and nutrient limitations.…”