CBET-EPSRC: Characterizing the effects of supply hours and pressure of intermittent piped water supplies on water quality

Lead Research Organisation: University of Sheffield
Department Name: Civil and Structural Engineering

Abstract

This project will study the effect that regular loss of pressure in water distribution systems has on water quality through a collaboration between the University of Massachusetts Amherst in the US and the University of Sheffield in the UK. The research will produce a better understanding of the effect of intermittently operated piped water systems on water quality and the results can be used to develop strategies to reduce the spread of waterborne diseases.
The influence of momentary loss of pressure due to pressure transients in continuous distribution systems has been relatively well-studied. However, while there is evidence of contamination in intermittent systems and corresponding adverse health impacts, there have been few studies exploring the mechanisms affecting water quality in chronically intermittent systems. The practice of intermittent water supply (IWS) can exacerbate risks to water quality that are observed in continuous supplies by introducing atypical hydraulic conditions imposed by the four phases of an IWS supply cycle. First, when the supply is off in the distribution network, pipes are at low or atmospheric pressure and may be partially or fully empty, thereby permitting entry of contaminants through leaks from adjacent groundwater or sewage depending on the conditions. Second, the water supply is then turned on to the pipes, filling the pipes with water and possibly mobilising contaminants accumulated at the pipe wall. Third, the pipes provide pressurized supply for a limited period of time, thereby transporting the mobilised material. Finally, supply is turned off again, leaving water in pipes to drain through household connections and leaks. While these hydraulic conditions can affect many aspects of the biological, chemical, and physical quality of the water, one of the most significant health concerns is the potential for intermittency to introduce waterborne pathogens into these distribution systems and to influence their transport, survival, and growth.

Our previous work hypothesized that the main mechanisms affecting this microbiological water quality in an intermittent water supply are: 1) mobilisation of contaminants from the pipe wall interface and corresponding interactions with the bulk supply (specifically biofilms, loose deposits, and microbial growth); and 2) ingress of contamination from outside the pipe when pressure is low, through either intrusion or backflow. However, while results from our field studies of intermittently supplied networks at scale suggest these two mechanisms are important contributors to contamination as demonstrated by the presence of fecal-indicator bacteria, the relative importance of these two mechanisms has not been studied under controlled conditions. Gaining a more fundamental understanding of how interruptions of supply affect the microbiology of pipes will allow for development of strategies to control potential health risks in both chronically intermittent networks and during interruptions to otherwise continuous supplies, such as after main breaks and for seasonal water systems.

The research will use the internationally-unique 600m long temperature-controlled, real-scale pipe loop facility at the University of Sheffield alongside pilot scale test rigs to be constructed at the University of Massachusetts. The three hydraulically isolated loops in the Sheffield facility will be operated with different supply regimes (continuous supply, 12 hours of supply every day, and 12 hours of supply twice per week) to establish baseline quality parameters, determine the presence, composition, and function of microbial communities, study the biofilm structure and composition, and investigate the survival and growth of indicators of pathogens. The data generated from these experiments will be used to develop a quantitative microbial risk assessment model to evaluate the impact of varying hours of supply on the potential risk of waterborne disease.

Planned Impact

Water distribution systems are a critical control point for maintaining the quality of drinking water. In high-income countries which normally have continuously pressurised water supply, the important role of distribution systems in protecting public health has been re-enforced after extreme failures, for example in Flint, Michigan, which led to an outbreak of Legionella pneumophila, or during natural disasters such as hurricanes, which have led to interruptions to supply and contamination of distribution systems and source waters by pathogen-containing floodwater. In low- and middle-income countries, access to piped water has been increasing; however, rapid urbanisation and a changing climate are threatening the reliability of these systems, often leading to reduced quality of service in the form of sustained interruptions to supply. The contribution of this proposed work will be to elucidate the fundamental mechanisms by which interruptions to supply influence the microbial ecology and behaviour of pathogens in biofilms and in the bulk phase of the water supply. Ultimately, the goal of this research is to improve our ability to control waterborne disease in water supplies used for drinking by identifying the most appropriate methods for control and operation of water distribution systems under intermittent supply. The proposed research will open a new field of enquiry within water quality in distribution systems, which until now has focused almost exclusively on continuous systems, to positively impact society in high as well as low- and middle-income countries by leading to practicable strategies to improve water quality and therefore reduce risks to health.

In addition, this joint US-UK project will train researchers to engage in international collaborations and global workforces, particularly related to meeting the sustainable development goals. The US Accreditation Board for Engineering and Technology, Inc (ABET) introduced "professional skills" into its criteria for engineering education, which includes "the broad education necessary to understand the impact of engineering solutions in a global, economic, environmental, and societal context", and the US National Academies of Science, Engineering, and Medicine vision of an engineer in 2020 also emphasises the importance of developing professional and teamwork skills as well as understanding engineering in a global context. Engineering UK estimates that an additional 79,000 engineering graduates per year, with deep and broad understandings of global issues as part of their hybrid skill sets, will be needed in the UK through 2024.

Publications

10 25 50
 
Description While the laboratory investigations are currently ongoing so the majority of findings are yet to be seen, the engagement activities for this project have reached a number of water utility practitioners in South Africa to make them aware of potential water quality impacts of intermittent system operation. This increased understanding is helping those practitioners to persuade officials to support investment in water system upgrades and operational changes.
First Year Of Impact 2019
Sector Environment
Impact Types Societal,Policy & public services

 
Description GCRF QR Pump Priming - Intermittent Water Supply in Nepal
Amount £6,993 (GBP)
Organisation University of Sheffield 
Sector Academic/University
Country United Kingdom
Start 05/2019 
End 07/2020
 
Description GCRF QR Travel - ARUA Water Centre of Excellence Training
Amount £2,000 (GBP)
Organisation University of Sheffield 
Sector Academic/University
Country United Kingdom
Start 01/2020 
End 02/2020
 
Description PhD Studentship - Intermittent water supply systems
Amount £70,000 (GBP)
Organisation Government of Turkey 
Sector Public
Country Turkey
Start 10/2019 
End 10/2022
 
Description Collaboration with the University of Toronto 
Organisation University of Toronto
Country Canada 
Sector Academic/University 
PI Contribution Collaborating with academics at the University of Toronto to apply their models of intermittent supply systems to our experimental data.
Collaborator Contribution Application of models
Impact Journal publication is under preparation.
Start Year 2019
 
Description Impact of hydraulic factors on pressures in an intermittent supply system 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Vanessa Speight presented at the CCWI 2019 conference in Exeter, UK.
Year(s) Of Engagement Activity 2019
URL https://www.ccwi-2019.com/
 
Description Intermittent Water Supply Colloquium 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Dr Douterelo and Dr Weston attended the colloquium at Stellenbosch University, South Africa to present their research on intermittent water supply systems, meet with local consultants and supply chain companies, and conduct a field visit to a South African water utility.
Year(s) Of Engagement Activity 2019
 
Description Water Networks Short Course: Resilient Water Services 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Joby Boxall, Vanessa Speight, and Caroline Wadsworth co-organised and attended this 2-day practitioner workshop hosted by Stellenbosch University, Stellenbosch, South Africa to discuss international perspectives on resilient water services including intermittent system operation with a variety of water industry attendees.
Year(s) Of Engagement Activity 2019