This Programme Grant will accelerate the delivery of decentralised water technologies by bringing the most up-to-date bioscience and energy engineering to bear. It will re-write emerging design rules for engineering biology to ensure that off-grid environmental biotechnologies can be configured with confidence. Bespoke microbial treatment communities will be evolved using a new suite of high-throughput synthetic-biology inspired, experimental platforms. For rural populations and UK Islands and in the developing world, from sub-urban Bangkok to the Amazon and Arctic Canada, we will develop site-specific off-grid integrated heat/water technologies. We will develop low-cost sensors, real-time monitoring and adaptive control for remote distributed water infrastructure. With water technology companies, we will analyse how suites of technologies can be configured and controlled to shape new models for decentralised provision. Scottish Water will invest significantly in co-creating rural demonstrators and a mobile technology-demonstration platform for sustainable communities and with Northumbrian, Welsh Water and other utilities and stakeholders we will build momentum for a radically new low-carbon decentralised future for the water industry. Working with stakeholders, from communities to legislators, we seek to incentivise community-led infrastructure solutions and to modify regulation in ways that balance local stakeholder needs and global goals for decarbonising infrastructure. Working with professional bodies and innovation centres we will create a global centre of excellence in off-grid water provision, with the drive and passion to deliver transformational change; helping to deliver 2050 net-zero carbon and Sustainable Development Goal 6.

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.