Abstract: Rivers are many things. For millennia, they have provided humans with water, energy, and food. They are key transport and communication routes. And - just as importantly - they have always served as sewers for the societies living on their banks. To dive into the history of these dirty waters is also to dive into the history of microbiology. Building on William Budd’s 1856 description of sewage-polluted streams as a “continuation of the human intestine”, this lecture traces the history of Britain’s faecal flows as a driver of microbiological research and innovation. From Victorian sewage farms to phage-based wastewater surveillance and antimicrobial resistance (AMR), it shows how engagement with the faeces, chemicals, and microbes in our waterways has led to an increasingly ecological understanding of the intersection between human, animal, and environmental health.