Quantification of wastewater treatment resilience metrics

The aim of this project is to develop a metric to measure the resilience of the wastewater treatment plant.

UK water companies are developing their resilience strategy for wastewater service.

The aim of these strategies is to understand how the wastewater system will respond to extreme or exceptional shock and stress events, and the potential impact this will have on the service provided to customers and to the environment. Upon identifying resilience risk, interventions will be developed to mitigate for, adapt to, or cope with future challenges. These interventions will seek to futureproof service provision or facilitate it to recover rapidly thereby minimising service failure.

One focus area of the strategy is understanding the resilience of wastewater treatment processes. It is recognised that both stress and shock events, driven by climatic change, population growth, ageing infrastructure etc. will increase the variability of flows and loads of influent entering treatment works, and increase the occurrence of internal asset failures. The current asset base and system operation may be incapable of responding to these events in order to prevent failure, and as such these events have the potential to cause service disruption, environmental pollution and reputational damage.

Following the impacts described a strategy to develop this project could be defined in the steps below:

* How the extreme events can impact the wastewater treatment plants and how the plant cope and recover from such events
* How to quantify the stressors and probability of occurrence
* Quantify the impacts on the wastewater processes
* Which models and tools to use to link the impact on the wastewater processes

The methodology for establishing baseline treatment resilience involves stressing a system with a number of defined system failures, and recording the resultant strain.

System failures (stresses) are classified as either external (i.e. changes to the system input) or internal (i.e. changes within the system boundary). The stresses are applied at a number of varying magnitudes and durations to establish a range of possible strain profiles. The output of this analysis is a set of stress-strain curves. This methodology is applied to a 'Digital Twin' of the treatment works. This is a calibrated physical/biological/chemical model of the treatment works built up from individually represented process units.

Digital twins are now routinely applied in small scale and controlled environments, e.g. manufacturing processes or single asset operation. A wastewater treatment operation for a large water company presents a stiff challenge in science, computing and engineering terms for the specification and development of a digital twin. The scientific advances would involve:

a) Data acquisition and management for large, open systems with significant spatial extent
b) Description and simulation of the complex links in a "system of systems"
c) Development of a resilience metric requires consideration of a number of different aspects which are not straightforward to equate with conventional methods (e.g. financial, carbon, environmental)
d) Extension of the method from large works (with good data availability) to large numbers of smaller works with much less data availability poses an interesting problem in terms of uncertainty suggesting a stochastic approach

In order to ensure reliable, resilient and sustainable wastewater service provision both now and into the future, UK water companies are committed to understanding the impact of shock and stress events. This project will enable and enhance this understanding and allow for targeted investment to tackle the resilience challenge. Development of quantifiable metrics will enable resilience to be tracked.

Graduates from the WRIC programme will produce new knowledge across the disciplinary landscape and graduate to occupy professional roles of influence and authority which require a thorough understanding of the pathways by which knowledge and technology are adopted and put to socially significant use. The people and knowledge delivered through the CDT will improve the efficiency and effectiveness of the nation's >£5bn annual spend on water and water related infrastructure (OFWAT, 2017), improving its resilience and securing its value for society for generations to come. With ambitions to nurture domain experts who can flourish at the interfaces of scientific disciplines and economic/industry sectors, the impact imperative is a significant but stimulating challenge for the WRIC CDT. Our impact strategy seeks to; (i) ensure rapid dissemination of scientific insights, (ii) maximise awareness and uptake of research sponsored through the CDT, and (iii) improve professional and lay understandings of the water infrastructure challenges facing society and the science behind candidate solutions. This strategy has been developed with project and Centre stakeholders so as to leverage additional resources, and maximise impact.
Improving the resilience of water infrastructure systems will be of benefit to a wide range of stakeholders. Given the CDT's bold intention to tackle knowledge gaps at the interfaces between disciplines and problems, new scientific understandings generated through WRIC will be of value to the knowledge users in the public sector (local authorities, regulators) and private sector (utilities, consultancies, technology providers), ultimately benefiting both lives and livelihoods across the UK and beyond. The UK economy will benefit from robust and resilient water infrastructure, in-line with the UK Government's Industrial Strategy for cleaner economic growth, the efficient use of resources, and building a regenerative circular economy. In the next Price Review PR19 (2020-25), water companies will be financially rewarded for implementing enhanced system resilience and innovation. Research outputs from WRIC will enable water companies to be able to meet these demands, alongside ambitious industry targets for zero water and wastewater quality failures, demand reduction and chemical recycling (OFWAT, 2017; UKWIR, 2017). These developments will facilitate inward international investment, development of new technology providers and supply chains, and opportunities for exporting intellectual property and know-how worldwide, further benefiting the UK economy. Project partners, including Thames Water, Severn Trent Water, Atkins, Stantec, Datatecnics also benefit from access to high quality graduates and facilities. Furthermore, regulatory agencies (Environment Agency, Drinking Water Inspectorate) and the European Commission will see benefits from improved compliance to regulations and sustainability agendas (Water Framework Directive 2008/32/EC and Drinking Water Directive 2017/0332(COD)).
The CDT programme will benefit the UK Collaboratorium for Research on Infrastructure and Cities (UKCRIC) government investments (£138M). Sheffield, Cranfield and Newcastle Universities have all received capital grants through UKCRIC to fund industrial scale test facility and observatory facilities to form an Urban Water Hub. The CDT will supply the resources to use and maximise the benefits and outputs from these facilities. Cooperation with other UKCRIC CDTs will help students better understand contemporary challenges for infrastructure and cities will catalyse horizontal innovation transfer and elevate the transformative potential of WRIC graduates.