Quantification of wastewater treatment resilience metrics

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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 processesThe 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 extentb) 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 approachIn 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.