To Chlorinate or Not to Chlorinate
Lead Research Organisation:
University of Sheffield
Department Name: Civil and Structural Engineering
Abstract
The majority of countries around the world maintain a disinfectant residual to control planktonic microbial contamination and/or regrowth within Drinking Water Distribution Systems (DWDS). Conversely, some European countries prohibit this practice because the residuals react to create disinfection by-products, which are regulated toxins with carcinogenic effects. Critically, the impact of disinfectant residuals on biofilms is unknown, including their role in creating a preferential environment for pathogens.
Biofilms grow on all surfaces; they are a matrix of microbial cells embedded in extracellular polymeric substances. With biofilms massively dominating the organic content of DWDS, there is a need for a definitive investigation of the processes and impacts underlying DWDS disinfection and biofilm interactions such that all the risks and benefits of disinfection residual strategies can be understood and balanced. This balance is essential for the continued supply of safe drinking water, but with minimal use of energy and chemicals.
The central provocative proposition is that disinfectant residuals promote a resistant biofilm that serves as a beneficial habitat for pathogens, allowing pathogens to proliferate and be sporadically mobilised into the water column where they then pose a risk to public health. This project will, for the first time, study and model the impact of disinfectant residual strategies on biofilms including pathogen sheltering, proliferation, and mobilisation to fill this important gap in DWDS knowledge.
The potential sources of pathogens in our DWDS are increasing due to the ageing nature of this infrastructure, for example, via ingress at leaks during depressurisation events. Volumes of ingress and hence direct exposure risks are small but could seed pathogens into biofilm, with potential for proliferation and subsequent release.
An integrated, iterative continuum of physical experiments and modelling is essential to deliver the ambition of the proposed research. We will make use of the latest developments in microbiology, internationally unique pilot scale experimental facilities, population biology and microbial risk assessment modelling to understand the interactions between the disinfection residuals, biofilms, pathogens and hydraulics of drinking water distribution systems. This research will combine globally renowned expertise in mathematical modelling, drinking water engineering, quantitative microbial risk assessment, and molecular microbial ecology to deliver this ambitious and transformative project.
If the central proposition is proven, then current practice in the UK and the majority of the developed world could be increasing health risks through the use of disinfectant residuals. The evidence generated from this research will be central to comprehensive risk assessment. A likely outcome is that by testing the hypothesis, we will prove under what conditions the selective pressures on biofilms are unacceptable, and in so doing understand and enable optimisation of disinfection residuals types and concentrations for different treated water characteristics. Although focused on the impacts of disinfectant residuals and pathogens, the research will also generate wider knowledge of biofilm behaviour, interactions and impacts between biofilms and water quality within drinking water distribution systems in general and relevant to other domains.
The impact of this research will be to deliver a step change in protecting public health whilst minimising chemical and energy use through well informed trade-offs between acute drinking water pathogen (currently unknown) and chronic disinfectant by-product (known and increasing) exposure. The ultimate beneficiaries will be the public, society and economy due to the intrinsic link between water quality and public health.
Biofilms grow on all surfaces; they are a matrix of microbial cells embedded in extracellular polymeric substances. With biofilms massively dominating the organic content of DWDS, there is a need for a definitive investigation of the processes and impacts underlying DWDS disinfection and biofilm interactions such that all the risks and benefits of disinfection residual strategies can be understood and balanced. This balance is essential for the continued supply of safe drinking water, but with minimal use of energy and chemicals.
The central provocative proposition is that disinfectant residuals promote a resistant biofilm that serves as a beneficial habitat for pathogens, allowing pathogens to proliferate and be sporadically mobilised into the water column where they then pose a risk to public health. This project will, for the first time, study and model the impact of disinfectant residual strategies on biofilms including pathogen sheltering, proliferation, and mobilisation to fill this important gap in DWDS knowledge.
The potential sources of pathogens in our DWDS are increasing due to the ageing nature of this infrastructure, for example, via ingress at leaks during depressurisation events. Volumes of ingress and hence direct exposure risks are small but could seed pathogens into biofilm, with potential for proliferation and subsequent release.
An integrated, iterative continuum of physical experiments and modelling is essential to deliver the ambition of the proposed research. We will make use of the latest developments in microbiology, internationally unique pilot scale experimental facilities, population biology and microbial risk assessment modelling to understand the interactions between the disinfection residuals, biofilms, pathogens and hydraulics of drinking water distribution systems. This research will combine globally renowned expertise in mathematical modelling, drinking water engineering, quantitative microbial risk assessment, and molecular microbial ecology to deliver this ambitious and transformative project.
If the central proposition is proven, then current practice in the UK and the majority of the developed world could be increasing health risks through the use of disinfectant residuals. The evidence generated from this research will be central to comprehensive risk assessment. A likely outcome is that by testing the hypothesis, we will prove under what conditions the selective pressures on biofilms are unacceptable, and in so doing understand and enable optimisation of disinfection residuals types and concentrations for different treated water characteristics. Although focused on the impacts of disinfectant residuals and pathogens, the research will also generate wider knowledge of biofilm behaviour, interactions and impacts between biofilms and water quality within drinking water distribution systems in general and relevant to other domains.
The impact of this research will be to deliver a step change in protecting public health whilst minimising chemical and energy use through well informed trade-offs between acute drinking water pathogen (currently unknown) and chronic disinfectant by-product (known and increasing) exposure. The ultimate beneficiaries will be the public, society and economy due to the intrinsic link between water quality and public health.
Organisations
- University of Sheffield (Lead Research Organisation)
- Biotechnology and Biological Sciences Research Council (Co-funder)
- Dwr Cymru Welsh Water (United Kingdom) (Collaboration, Project Partner)
- UK Water Industry Research (Collaboration, Project Partner)
- Northumbrian Water (Collaboration)
- Anglian Water Services (Collaboration)
- Kelda Group (United Kingdom) (Collaboration, Project Partner)
- Severn Trent Water (Collaboration)
- UNITED UTILITIES GROUP PLC (Collaboration)
- Swiss Federal Institute of Aquatic Science and Technology (Project Partner)
- United Utilities (United Kingdom) (Project Partner)
- Imperial College London (Project Partner)
- Nephros, Inc. (Project Partner)
- Morrison Utility Services (Project Partner)
- Drinking Water Inspectorate (Project Partner)
- Severn Trent (United Kingdom) (Project Partner)
- Georgia Institute of Technology (Project Partner)
- Anglian Water Services (United Kingdom) (Project Partner)
- Northumbrian Water Group plc (Project Partner)
- UK Health Security Agency (Project Partner)
- John Fawell (Project Partner)
- Southern Cross University (Project Partner)
- Citrox Biosciences Ltd (Project Partner)
- Scottish Water (United Kingdom) (Project Partner)
- Drinking Water Quality Regulator (Project Partner)
- City of Montreal (Project Partner)
Publications
Kyritsakas G
(2023)
Forecasting bacteriological presence in treated drinking water using machine learning
in Frontiers in Water
Park JW
(2023)
Predicting heterotrophic plate count exceedance in tap water: A binary classification model supervised by culture-independent data.
in Water research
Pick F
(2024)
Emerging investigator series: Optimisation of Drinking Water Biofilm Cell Detachment and Sample Homogenisation Methods for Rapid Quantification via Flow Cytometry
in Environmental Science: Water Research & Technology
Tsagkari E
(2023)
The Role of Chlorine in the Formation and Development of Tap Water Biofilms under Different Flow Regimes
in Microorganisms
Description | EPSRC Centre for Doctoral Training in Water Infrastructure & Resilience II (WIRe II) |
Amount | £8,174,028 (GBP) |
Funding ID | EP/Y035178/1 |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 03/2024 |
End | 09/2032 |
Description | Collaboration with Anglian Water |
Organisation | Anglian Water Services |
Country | United Kingdom |
Sector | Private |
PI Contribution | Anglian Water have been an active member of our steering committee |
Collaborator Contribution | project steering committee |
Impact | policy and practice in AW |
Start Year | 2009 |
Description | Collaboration with Northumbrian Water |
Organisation | Northumbrian Water |
Country | United Kingdom |
Sector | Private |
PI Contribution | Collaboration with Severn Trent Water / United Utilities / Northumbrian Water throughout the course of the project in the application of the created technology to real world treatment and supply conditions (e.g. collection and monitoring of sample waters). |
Collaborator Contribution | Membership of steering committee, direction, advice, comparative analysis and field testing |
Impact | Field testing leading to reports, publications and follow on funding |
Start Year | 2011 |
Description | Collaboration with Severn Trent Water |
Organisation | Severn Trent Water |
Country | United Kingdom |
Sector | Private |
PI Contribution | Collaboration with Severn Trent Water / United Utilities / Northumbrian Water throughout the course of the project in the application of the created technology to real world treatment and supply conditions (e.g. collection and monitoring of sample waters). |
Collaborator Contribution | Membership of steering committee, direction, advice, comparative analysis and field testing |
Impact | Field testing and comparative analysis leading to reports, publications and further funding |
Start Year | 2011 |
Description | Collaboration with United Utilities |
Organisation | United Utilities Group PLC |
Country | United Kingdom |
Sector | Private |
PI Contribution | United Utilities have been an active member of the project steering committee |
Collaborator Contribution | project steering committee |
Impact | Policy and practice within UU |
Start Year | 2008 |
Description | Collaboration with Welsh water |
Organisation | Welsh Water |
Country | United Kingdom |
Sector | Private |
PI Contribution | Active member of project steering group |
Collaborator Contribution | Research strategy and directions |
Impact | research input and other research ideas / projects |
Start Year | 2022 |
Description | Collaboration with Yorkshire Water |
Organisation | Yorkshire Water |
Country | United Kingdom |
Sector | Private |
PI Contribution | Yorkshire Water have been an active member of the steering group for this project |
Collaborator Contribution | project steering committee |
Impact | policy and practice in YW |
Start Year | 2009 |
Description | UK Water Industry Research |
Organisation | UK Water Industry Research Ltd |
Country | United Kingdom |
Sector | Charity/Non Profit |
PI Contribution | research outputs and outcomes, strategic direction |
Collaborator Contribution | Active members of project steering board, match funding |
Impact | tbc |
Start Year | 2021 |
Description | A talk to Saline Water Conversion Corporation (SWCC), a Saudi governmental institution |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Industry/Business |
Results and Impact | Professor Joby Boxall gave a talk and led debate on innovation in the water sector and drinking water quality |
Year(s) Of Engagement Activity | 2024 |
Description | Speaking to House of Lords Select Committee on the Built Environment |
Form Of Engagement Activity | A formal working group, expert panel or dialogue |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Policymakers/politicians |
Results and Impact | Professor Joby Boxall was invited to speak to the House of Lord Select Committee on the Built Environment, private session on the 7th February 2023 |
Year(s) Of Engagement Activity | 2023 |
Description | Talk at WWT 'Drinking Water Quality Conference' |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Professional Practitioners |
Results and Impact | Professor Joby Boxall gave a talk on 'Using AI to unlock water company data to help manage discolouration and iron compliance' |
Year(s) Of Engagement Activity | 2023 |
Description | Talk to the the MOST-BMBF funded project MoDiCon (Germany / Israel) |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | Professor Joby Boxall gave a talk on innovation in the water sector and drinking water quality |
Year(s) Of Engagement Activity | 2024 |
Description | To Chlorinate Launch event |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Professional Practitioners |
Results and Impact | Project launch event, wide representation from across the water sector including practitioners, policy makers and regulators |
Year(s) Of Engagement Activity | 2023 |
URL | https://www.tochlorinate.ac.uk/launch-event |
Description | Visit from and presentations to OfWat |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Policymakers/politicians |
Results and Impact | Hosted a visit from OfWat to talk about innovation and water quality, a series of presentations from University of Sheffield water research, tour of facilities and discussions |
Year(s) Of Engagement Activity | 2023 |
Description | Water UK / Water Industry Forum 'The challenges of AMP8' |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Professional Practitioners |
Results and Impact | Professor Joby Boxall gave a talk at a Water UK / WIF event on 'roadmap for the furture of water innovation' |
Year(s) Of Engagement Activity | 2023 |