Automation of on-site microbial water quality monitoring from source to tap: Challenges and perspectives

• Increasing adoption of automated on-site monitoring of microbial water quality • Review latest developments in sensor technologies and microbial target parameters • Elucidate key terminology, critically discuss recent use cases from source to tap • Automated on-site monitoring for improved operational risk-based management • Insights from drinking water utility survey to discuss barriers to widespread adoption Ensuring the provision of safe drinking water necessitates thorough monitoring of microbial water quality. While traditional culture-based enumeration of bacterial indicators has served as the gold standard in compliance monitoring since the late 19 th century, recent advancements in microbial sensor technology, driven by automation and digitalization, are revolutionizing on-site monitoring capabilities. These innovations offer unparalleled potential for automated, high-temporal-frequency monitoring with remote, real-time data transmission. With regulatory frameworks increasingly favouring risk-based approaches to microbial risk management throughout the drinking water supply chain, we are witnessing a paradigm shift towards the adoption of microbial sensors. This review offers a comprehensive examination of the latest developments and accomplishments in automated on-site monitoring of microbial water quality. Beginning with an elucidation of key terminology and an overview of available sensor technologies, we explore how these cutting-edge tools can enhance our understanding of microbial dynamics in the sourcing, treatment, and distribution of drinking water, and how this knowledge can be translated into operational management. Despite the promise of microbial sensors, significant challenges remain. Drawing from insights gathered from an international online survey targeting drinking water utilities, we discuss the analytical, economic, and legal barriers that must be overcome for the implementation of automated on-site monitoring of microbial water quality. This review serves as a vital resource for researchers, utilities, and policymakers operating in water microbiology and sensor technology. While it is addressing drinking water more specifically, the presented concepts and tools can be extrapolated to recreational waters or wastewater management, with the shared goal to ensure sustainable management of water resources and protection of public health.