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Paper short abstract:

Activated sludge is the standard approach used to treat wastewater across the world. Spanning empirical historical work from Berlin and London, this presentation re-conceives activated sludge as a more-than-human collaboration between humans and microbes for socio-ecological urban reproduction.

Paper long abstract:

On the hundredth anniversary of the activated sludge process, environmental historian Daniel Schneider posed a seemingly straightforward question: "Who invented activated sludge?" The activated sludge process is the standard approach used to treat wastewater across the world, in which communities of bacteria oxidise nutrients and decompose organic pollutants in industrial and urban effluent. Schneider's commentary gives historical context to the development of the activated sludge process, raises questions over whether it was 'invented' or 'discovered', and characterises the cynical legal battles over patent rights that followed its development. In light of recent theoretical developments across more-than-human geography and the wider "non-human turn" in the social sciences and humanities, however, it might be suggested that the microorganisms involved in activated sludge were also complicit in its invention. Hence, activated sludge is a more-than-human achievement of hybrid labour, in which humans and microorganisms achieve the (re)circulation of, primarily human, waste. As human societies undergo material reconfigurations, the composition of the effluent which these microorganisms come into contact with also changes, and a significant minority of metabolic processes occurring in contemporary activated sludge are novel, compared to the well characterised 'core' features of nitrification and phosphate removal: The microbial communities involved are continually experimenting and 'inventing' in response to the chemical diversification of late modernity. Based in theories of non-human labour and creativity, this presentation spans historical empirical work undertaken in the cities of London and Berlin to a discussion of contemporary experiments with sludge-as-resource for improving the urban carbon footprint.