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

Abstract

Temperature variation can promote physico-chemical and microbial changes in the water transported through distribution systems and influence the dynamics of biofilms attached to pipes, thus contributing to the release of pathogens into the bulk drinking water. An experimental real-scale chlorinated DWDS was used to study the effect of increasing temperature from 16 to 24°C on specific pathogens, bacterial-fungal communities (biofilm and water samples) and determine the risk of material accumulation and mobilisation from the pipes into the bulk water. Biofilm was developed for 30 days at both temperatures in the pipe walls, and after this growth phase, a flushing was performed applying 4 gradual steps by increasing the shear stress. The fungal-bacterial community characterised by Illumina MiSeq sequencing, and specific pathogens were studied using qPCR: Mycobacterium spp., Mycobacterium avium complex, Acanthamoeba spp., Pseudomonas aeruginosa, Legionella pneumophilia, and Stenotrophomonas maltophilia. Sequencing data showed that temperature variation significantly modified the structure of biofilm microbial communities from the early stages of biofilm development. Regarding bacteria, Pseudomonas increased its relative abundance in biofilms developed at 24°C, while fungal communities showed loss of diversity and richness, and the increase in dominance of Fusarium genus. After the mobilisation phase, Pseudomonas continued being the most abundant genus at 24°C, followed by Sphingobium and Sphingomonas. For biofilm fungal communities after the mobilisation phase, Helotiales incertae sedis and Fusarium were the most abundant taxa. Results from qPCR showed a higher relative abundance of Mycobacterium spp. on day 30 and M. avium complex throughout the growth phase within the biofilms at higher temperatures. The temperature impacts were not only microbial, with physical mobilisation showing higher discolouration response and metals release due to the increased temperature. While material accumulation was accelerated by temperature, it was not preferentially to either stronger or weaker biofilm layers, as turbidity results during the flushing steps showed. This research yields new understanding on microbial challenges that chlorinated DWDS will undergo as global temperature rises, this information is needed in order to protect drinking water quality and safety while travelling through distribution systems.

Efficient nested-PCR-based method development for detection and genotype identification of Acanthamoeba from a small volume of aquatic environmental sample

“…Moreover, the high prevalence of the Acanthamoeba T4 genotype in aquatic environments indicates a potential threat to public health. According to the history of patients diagnosed with AK and GAE, wearing contact lenses and contact with recreational/agriculture water were the main risk factors, while soil/dust as a source of infection and the effect of climate change require a thorough investigation 48 – 52 . Overall, along with the detection of contamination sources and accurate estimation, better hygiene, implementation of disinfection methods, and pathogen safety measures are warranted to avoid the risk of Acanthamoeba infection.…”

Water quality trade-offs for risk management interventions in a green building

“…Fluctuating warm water temperatures favor microbial growth in the waterlines and influence the biofilm dynamics in these pipes, and thus could contribute to release of pathogens in the bulk drinking water. 66 Material accumulation forming deposits in the waterlines may also accelerate with temperature along with metal releases in water. 66…”

The Impact of Ground Heat Capacity on Drinking Water Temperature

“…But if we consider that >95% of organics including bacteria are in biofilms that are fixed to the pipe walls throughout DWDS (Douterelo et al 2018), these temperature effects will be important. This is amplified when considering that accelerated growth in summer (due to increased temperature - Calero et al 2021) or die off (due to the reverse) in winter will seed the entire network. The same applies to reaction precipitations (like iron and manganese), which determine discolouration (Mounce et al 2016).…”

“…This is important for the operation of DWDS, as many countries aim to ensure a minimum target level of disinfectant at the customer tap to minimise risks to public health (WHO 2011). Temperature is also known to affect bacterial-fungal communities (Calero et al 2021) and precipitation reactions like iron and manganese (Mounce et al 2016), potentially contributing to discolouration. At present, there is hardly any temperature monitoring, so it is not easy to see trends and/or quantify the implications of temperature increase on water quality (Agudelo-Vera et al 2020).…”