Bathing in black water? The microbiopolitics of the River Seine’s ecological reclamation

Marine Legrand, Germain Meulemans


In 2017, in the wake of Paris’s bid to host the Olympic Games, the French capital’s mayor announced that the swimming and triathlon competitions would take place not in a regular Olympic pool but in the River Seine. For the local authorities, as well as those of several other large European cities, letting people once again bathe in the river was a strong symbol of their achievement regarding the ‘ecological reclamation’ of urban watercourses. However, this new objective spurred concerns over a return of ‘faecal peril’ in Paris – a central topic for public health that points to the risk of human infection by faecal bacteria present in drinking or bathing water (WHO 2000). What happens when a river becomes part of the ‘domestic space’ of the city it was meant to clean up by collecting and evacuating dirtiness away? How are human-microbe relations reconfigured when the field of sanitation – largely informed by a Pasteurian ethic of concealing pathogens – and the field of river management – now largely informed by the field of water ecology – meet? And how does this impact the humans and non-human agents that live in or near rivers?

This chapter describes how microbes – E. coli in particular – came to matter in the field of river management once the mayor of Paris announced that the Seine River would be made ‘bathable’ for the Olympic Games in 2024. On the basis of an ethnography conducted in the Paris region among sanitation and river management actors,1 and a review of recent technical and legal documents related to the River Seine, we describe how different categories and actors are mobilised over time in the management of the river, and how these enact different trajectories for human-microbe microbiopolitics (Paxson 2008). To do this, we unpack the ambivalent and multiple relationships between humans, water and microbes by attending to shifts in the modes of regulatory attention, in scientific and expert repertoires and epistemologies as well as in infrastructure design priorities. Then, we examine how new concerns over the microbiological quality of the river led a handful of houseboats moored on the Seine to be identified as a new biohazard, which in turn triggered a controversy surrounding the overreliance on centralised hydraulic networks within the sanitation system. This example shows how, far from being only technical, the debates surrounding sanitation and water quality raise questions relating to appropriate human behaviour and modes of dwelling.

Water quality: From hydrobiology to river ecology

Over the past two centuries, the discipline most associated with both sanitation and river management has been civil engineering. Many of the fundamental principles that have shaped sanitation can be linked to hygienism, a movement at once ideological, political, technological and scientific, which played a major role in every aspect of French society between the middle of the nineteenth century and the beginning of the twentieth century (Barles 1999). In particular, this movement played a crucial role in urban planning and the design of urban services, among which sanitation appears emblematic. The current conventional sanitation paradigm relies largely on water, which is used in combination with pipes to ensure the transport of dirtiness away from inhabited places. Above all, it seeks to contain and control human excreta (also called black water when it is flushed away) and its microbial content. During the twentieth century, rivers were strongly enrolled in sanitation socio-technical devices. And, with the building of centralised sanitation networks, they were envisioned and conceptualised predominately through a reticular paradigm and, hence, through a hydraulic lens (Barraqué 2014). In the past 50 years, however, as environmental issues have become matters of concern, disciplines pertaining to the biological sciences (hydrobiology, ecology, and finally microbiology) have gained new traction in the relations between sanitation and river management.

Dilution: Hydrobiology and the self-purification of rivers

The faecal contamination of rivers was already a subject of controversy when urban centralised sanitation systems started to develop at the end of the nineteenth century (Aguerre 2003; Barles 2005). Nevertheless, it gradually stopped being a matter of concern when sewers became the virtually exclusive model for urban excreta management, and only quite recently made a comeback in the field on sanitation. Whereas in the first half of the twentieth century, sanitation was guided by a quantitative objective to extend the sewerage networks as much as possible, the 1960s saw the emergence of concerns about improving the health of aquatic environments. From the 1970s up to and including the 1990s, EU directives were introduced to regulate the pollution emitted by industry, agriculture and cities (Barraqué 2001). In addition to toxic industrial substances (heavy metals, etc.), these directives stipulated emission norms regulating the amount of organic residues, nitrogen and phosphorous that were present in wastewater when discharged into rivers, with the intent to prevent hypoxia and asphyxiation of aquatic life. These directives did not address bacterial contamination, except in specific cases such as drinking water catchment areas or shellfish farming. In response to the establishment of these standards, much effort was made to improve the sanitation equipment, which resulted in the development of modern wastewater treatment plants, designed to remove suspended solids, organic matter, nitrogen and phosphorus, although not faecal microorganisms.

From the 1960s onwards, the interpretation of the impacts of wastewater on rivers was largely shaped by hydrobiology, an approach which based its analysis of the aquatic environment on morphological, mechanical and physico-chemical parameters (Legay 2006). As a legacy of this era, the definition of standards for the discharge of organic matter, nitrogen and phosphorous is still based on an approach which considers that sanitation continues in rivers: the receiving environments participate in eliminating the waste that is discharged into them. This is referred to as the ‘self-purification’ of rivers. In a conventional centralised sanitation system, the river is therefore not only an outlet for the treatment system but is enrolled as the last link in the chain of the treatment process by diluting, taking away and digesting remaining contaminants. Hydrobiologists estimate rates of dilution and biodegradation through a ratio between the flow of the watercourse, its speed and degree of slope – factors on which its oxygenation depends (Dubin 1971). This has always been seen as a problem in Paris, which is a ‘mega city on a small river’, as the Seine flows too slowly through the Paris conurbation to fulfil this dilution role properly (Tabuchi et al. 2016: 9).

Ecologisation: Sentinel species look out for the river’s ‘good ecological status’

In 2000, the Water Framework Directive (WFD) inaugurated a different approach, focusing on the development of a territorial management of water bodies as a whole. The WFD introduced the ambitious objective of achieving the ‘good ecological status’ of all European water bodies within 15 years. This marks the beginning of a period of ecologisation of river management, in which the good health of the aquatic environment becomes a key criterion for assessing the performance of sanitation systems. The discipline of stream ecology then gained legitimacy in the watercourse management sector, and this prominence was reinforced by the various European directives on water quality that followed in the 2000s.

For ecologists, a ‘good ecological status’ does not refer to a ‘pristine’ state of rivers but rather to their capacity to accommodate the reproduction of aquatic biodiversity. The rise of this notion overshadowed the previously central hydrobiological notions of dilution and self-purification: once rivers appeared as ecosystems to be protected, any pollution introduced into them was likely to provoke ecological disturbance.2 Monitoring the health of rivers now implied the study of a set of aquatic species, primarily fish. Rather than being framed as a ‘fish stock’ to be managed and replenished by fishing federations, as had been the case since the 1940s (Bouleau 2017), fish, along with many other organisms, were now taken into account as ‘bioindicators’ of river health.

A bioindicator is a species or group of species whose presence, absence or abundance provides information about the ecological status of the environment (Blandin 1986). Sociologist Christelle Gramaglia (2013), who has documented the use of molluscs to monitor water quality and lichens to test air pollution, refers to these as ‘sentinel’ species. Sentinels are involved in environmental monitoring projects and ‘look out for the environment’ by detecting signs that would otherwise be invisible to humans – especially pollution. Gramaglia explains that the effectiveness of a sentinel depends on its embeddedness in the monitored environment, its ability to express stress or preference, but also on the ability of the scientists or technicians who follow it to understand the vital relationships it has with its world. In the case of river ecological monitoring, fish like trout and salmon are ideal sentinels because they offer an integrative vision of the state of the watercourse, given their place at the end of the food web. Depending on the context, dragonflies, shellfish and sedimentary worms are also targeted; each type of species provides specific information (UNCPIE 2015).

In addition to older emission standards, river ecology itself became the main indicator for the environmental efficiency of the sanitation systems. However, the territorial management system, structured by negotiations between stakeholders with different interests and negotiating weight, and surrounded by scientific controversies about the definition of indicators, has been criticised by both researchers and river managers for its slowness in reducing aquatic pollution by wastewater discharges, and WFD environmental objectives are far from being achieved in France (Maillet 2015).

Making the Seine bathable: How microbes became a key concern in river management

Throughout the 2010s, the Paris metropolitan area, like other European cities, has become the scene of a political and epistemic turning point in terms of public action in the field of sanitation. In Paris, urban bathing is quickly emerging as a key political priority, spurred on by the French capital’s bid to host the 2024 Olympic Games. Having become the new benchmark for river health, this theme reinforces the break with the paradigm of self-purification by introducing a new key actor in the debate: the presence of faecal pathogens in rivers.

Urban bathing as a regional political issue

In the French capital, the idea of making the Seine bathable is a perennial subject in local politics. Many people remember one of Jacques Chirac’s favourite promises to soon allow people to ‘swim in the Seine’, first made in 1988, and later taken up by successive mayors. Bathing in the River Seine in Paris became restricted to certain locations in the eighteenth century, originally for reasons of decency. It became entirely prohibited in the twentieth century, first because of conflicts with boat traffic, then because of pollution issues and the general degradation of water quality. Even though many among the working class continued to bathe despite the regulations, the redevelopment of the banks into expressways in the 1970s put an end to these activities (Duhau 2007; Le Bas 2020).

From the 1990s onwards, various citizen and institutional movements to reclaim the riverbanks changed the situation. The river began to be seen as a natural heritage, while several of its tributaries that had been buried were rehabilitated. Open water bathing in the city’s river became a symbol of the successful reclamation of the aquatic environment and of sustainable urban development. In France, this idea was notably popularised by activist groups such as the Laboratory of Experimental Urban Swimming, which organises collective wild swims to campaign for the rehabilitation of urban swimming, a free and popular leisure activity. In Paris’s neighbouring departments, the establishment of a programme to reclaim the River Marne by the mixed syndicate Marne Vive has put the question of open water bathing on the political agenda. At the same time, ‘wild bathing’ became more frequent again because of a succession of summer heat waves that struck Paris over the past twenty years, and some sites were officially reopened for bathing in 2017.

As noted by Haghe and Euzen (2018), a new political categorisation of water quality is now on the rise, centred around the diptych bathable/non-bathable. In a local context marked by competition between urban authorities whose legitimacy is being questioned (City of Paris, Greater Paris, region, Ile-de-France departments),

[t]he political temptation is strong to set up a quality indicator for the Seine and Marne that is popular, simple to understand and a guarantee for the good governance of water and the environment, and that replaces indicators considered by elected officials and citizens as incomprehensible because they are too technical (ibid.: 2).

Moreover, bathing makes it possible to convey the good ecological state of the river through people’s ‘lived experience’. From the beginning of the 2010s, public administrators started to see bathing as a promising way to mobilise groups around this issue.3

In 2017, the designation of Paris as the host city for the 2024 Olympics accelerated the process, as the Paris Mayor’s office soon promised that the river water would be of good enough quality to swim in by 2024. The hope of this project was to hold the triathlon and freestyle swimming competitions of the Olympics directly in the river, next to the Eiffel Tower. Beyond the Olympics, the authorities seized the opportunity of developing new recreational uses, with the creation of over 20 bathing sites in the urban area. In Paris, green policies are clearly seen as a tool for asserting the city’s position as an international metropolis. The mayor’s office sees the completion of a three-decade-long effort to raise the river’s ecological quality as the fulfilment of this green policy, arguing that there are 35 species of fish in the river today, compared to only two in the 1970s. As such, a member of the City Council’s sanitation team described the project as ‘going far beyond a bathing project’, as a way to ‘speed things up in regards to how we comply with EU regulations’.4 Thus, having returned the Seine to eels, trout and pike, the ambition to give it back to human Parisians appeared to be a strong symbol of the ‘ecological reclamation’ of the aquatic environment.5

Microbiologisation: E. coli and its procession

The political project to make bathing a marker for the river’s good ecological status materialised through the creation of a steering committee on ‘Water Quality and Bathing in the Marne and Seine’ (here, we will refer to it as the Bathing Committee) in spring 2016, in the context of Paris’s bid for the Olympic Games. Co-chaired by the mayor of Paris and the regional prefect, this committee includes local mayors and all the public and private actors of sanitation and water management. The Bathing Committee’s priorities include the selection of 23 sites suitable for bathing in 2018, as well as the organisation and coordination of measures designed to make the Seine bathable.6 The committee also takes on the role of gathering a larger set of actors and presenting urban bathing as a unifying issue among the regional population. Above all, however, its creation brings the issue of faecal contamination to the forefront as a quality criterion for the aquatic environment, where this human health issue had previously been a minor concern in this context. Indeed, the objective of making the Seine bathable is to shift the regulatory framework from the WFD to that of the Bathing Directive.

Within this new normative framework, new areas of expertise are being called upon to assess the state of the environment and to remedy established contamination. After the ecologisation of river management in the 1990s–2000s, new ways of considering the river are this time accompanied by a ‘microbiologisation’, with growing importance and legitimacy given to pathogen microbiology in the field of river management. Even though EU regulations already required that public authorities (e.g. the City of Paris and the Marne Vive Syndicate) perform a routine monitoring of some of the main pathogens in the river, these measurements were not analysed ‘scientifically’. Around 2010, however, a shift can be observed in the publications of Ile-de-France microbiologists working on faecal contamination, who initially carried out analyses on untreated and treated wastewater but gradually became involved in studies of the aquatic environment itself (lakes, leisure centres, river sites). These microbiologists would soon question the usual categories used in the routine monitoring performed by the authorities.

Based on the first WHO recommendations regarding the microbiological quality of waters, issued in the 1970s, specific European regulations for the management of the water quality of bathing areas appeared in 1975 (76/160/EU). Just like the regulations concerning the ecological status of rivers, regulations over the microbiological quality of bathing water became implemented through the monitoring of sentinel organisms that indicate the state of affairs on a larger scale. In this case, however, these sentinels are neither trout nor mussels but ‘faecal contamination indicator bacteria’ (FIBs), a microbiological concept originally aimed at assessing the quality of drinking water. It was developed at the beginning of the twentieth century, when it became obvious that waterborne diseases were mostly gastroenteritis-related (Horrocks 1901). The current EU bathing directive (2006/7/EC) defines thresholds of bathing water quality (excellent, good, sufficient and poor) based on the monitoring of two FIBs: Escherichia coli and intestinal enterococci, both residents of human and other mammal intestines. The presence of these easy-to-follow FIBs (that can be cultivated in the lab) is assumed to be a good indicator of the presence of other faecal pathogens:

When you talk about E. coli, you have to imagine the whole procession behind it, all the other faecal contaminants which we don’t even try to detect because it would be complicated, it would take too long. But we know that if E. coli is there, there is a good chance that there are also viruses, hepatitis A, polio, coronavirus (…) you have the whole cortege that comes with it.7

As a result of the search for increased bathing quality, new indicator species are being referred to, making E. coli a new sentinel of water contamination in large portions of rivers in the Ile-de-France region. The situation also changes the way in which E. coli is understood: instead of being a purely sanitary indicator, it also becomes an environmental indicator, based on the idea that the more water is swimmable for humans, the less untreated or poorly treated wastewater is discharged.

Interestingly, while E. coli and other FIBs are widely recognised bioindicators in professional circles dealing with water-related health issues, many microbiologists consider them to be a very imperfect indicator:

The presence of FIBs can predict the probable presence of viruses, Giardia, and Cryptosporidium in surface water affected by sewage inputs, but they cannot predict their concentration. This is in accordance with the original indicator concept in drinking water, which established FIBs as an index of faecal pollution and, therefore, the probability of the presence of pathogens and potential health risks (Mouchel et al. 2019: 8).

As we shall now see, this limitation in the reliability of FIBs contributed to reframing the debate as concerning the whole infrastructure of sanitation systems, and what it allows to flow into the receiving environment.

Recentralisation: Containing microbes in watertight pipes

In France, to obtain a swimming permit from the Regional Health Agency, the applicant must produce a ‘profile’ consisting of measurements taken over four consecutive years at different seasons and different points in the area and show that E. coli concentrations are lower than WHO thresholds (WHO 2003). However, the routine microbiological monitoring of the Seine confirmed that the concentration of faecal indicators should be reduced by up to twenty-fold in the summer months to reach an ‘excellent’ quality. It also detected specific viruses and parasites such as Giardia in the water. Hence, the approach of the Olympic Games soon made the headlines, as it compelled Paris to face its own ‘faecal peril’. Indeed, even though the Paris region sanitation system is considered efficient from a sanitary perspective, when looking at the water quality of rivers from a bathing perspective, it becomes clear that faecal pathogens are still in fact circulating in the environment: the medium through which pathogens are put in contact with human bodies is the river itself.

The Bathing Committee soon insisted that this faecal contamination should be treated in an exemplary way. The aim was to avoid repeating past incidents where pathogens that were not taken into account in WHO routine tests had threatened the health of athletes or bathers, such as during the Rio Olympics (WHO 2016). Since large-scale antiseptic treatment of the Seine was not an option, the authorities set out to identify and suppress the source of these microbes. This, however, shed light on the structural limits of the whole sanitation system. Indeed, as sanitation engineers often insist, not all the wastewater reaches a treatment plant before going into the river. First, in the event of heavy rains, the system can overflow in places where rain and wastewater are collected together, leading to the release of untreated or partially treated water into the aquatic environment (Passerat et al. 2011). This problem is known as ‘Combined Sewer Overflows’. Solving it requires a thorough review of rainwater management methods and relies on heavy investment. Second, in areas where rain and wastewater are collected separately, poorly made connections – places where wastewater is connected to the networks reserved for rainwater – result in wastewater being discharged directly into the river.8 The Bathing Committee therefore launched a campaign to identify and repair every ‘anomaly’ on the network – a long and tedious task, as bad connections are multiple, diffuse and mostly situated outside Paris.

Ironically, this aspect of the authorities’ response appeared to several observers as a revival of the modernist ambition to create a perfectly centralised and controllable watertight network. The strategies implemented by the Bathing Committee are reactivating this historical vision of sanitation, based on a ‘reticular’ approach (pre-eminence of the network) which prevailed globally throughout the twentieth century in the global North (Barraqué 2014). This emphasis on the confinement of wastewater flows in networks with a view to their optimised treatment in treatment plants, and the stress on FIBs as indirect bioindicators of the good health of rivers, thus signals a second move away from the dilution paradigm, since in relation to the bathing objective, any ‘leakage’ of faecal pathogens into the aquatic environment becomes a potential danger to human health. Thus, the ambition to control the microbiology of the Seine causes governance of aquatic environmental management to be recentralised, which overlaps with its territorialisation in the previous decade. However, as we shall now see, this movement of centralisation/watertightness also brought about a cascade of new and unexpected players in the socio-microbial assemblage.

‘Barge Gate’: Remaining off-grid through novel socio-microbial alliances

Fig. 6.1 In France, many houseboats are old commercial barges bought at a cheap price from retiring haulers in the 1970s and refitted by the buyers. The most common model is the ‘Freycinet’ barge (40 m long and 5 m wide), which offers up to 200 m2 of living space (photograph by F.R. Thomas).

There are about 170 private houseboats, 72 passenger boats and 62 floating establishments open to the public (bars, restaurants, hotels and some workplaces) that are regularly anchored in the area of the river relevant to the Olympics, bringing the total to around 1,000 boats at a regional level.9 Houseboats – inhabited boats that are moored most of the time – generally emit flows of untreated sewage, which means that their toilet system discharges directly into the river. In 2007, a study commissioned by the Paris boaters’ association and the local authorities showed that the presence of the houseboats did significantly raise FIB levels. Even though the study’s experts had recommended the implementation of quayside sewer connections and/or autonomous sanitation10, these discharges were not considered a priority, since the amount of waste that goes into the river remains, quantitatively speaking, quite incidental in comparison to the structural limitations of the sanitation system. Furthermore, ‘no legislation or guidelines mandate anything about the discharge of waste water. Direct discharge is prohibited by law, but no implementing decree exists due to the lack of standardisation of treatment equipment’.11 However, in 2017, after the opening of the black box of sanitation to many new actors, the Seine’s ‘faecal peril’ contributed to throwing these rather discreet actors into the spotlight.

Is a ship just another building?

The Bathing Committee encountered the issue of houseboat discharges as they were making a systematic and methodical inventory of every anomaly on the sanitation network. Following the same reasoning they had adopted regarding connection mistakes and clogged up sewers, they approached it as yet another anomaly to be corrected by ensuring the boats’ connection to the sanitation system. The 2018 Olympic law therefore excluded the option of implementing on-board sanitation in Paris intramuros and stated that every Seine houseboat within Paris would have to be connected to the sewer system by 2024. This would solve the problem of the River Seine’s direct faecal contamination by boats in the sense that they would be, from this point on, subject to the same sanitation standards as any dwelling in the city.

The choice of connecting boats to the sewers, however, also involved a different agenda, that of HAROPA, the firm that manages the riverbanks for the city of Paris. Originally specialising in freight logistics and river traffic management, HAROPA recently took charge of providing services to port users (such as drinking water and electricity). Hoping to generate new sources of revenue by developing spaces such as the banks of the Seine, which were in the process of being pedestrianised, HAROPA started lobbying to equip all the ports and banks of Paris with sewer connection points, which would ease the development of floating establishments dedicated to economic activities (hotels, restaurants, bars and other various leisure venues). This quickly generated multiple conflicts with houseboat owners, who see the development of these businesses as a ‘colonisation’ of the riverbanks. As a representative of houseboat owners puts it:

Only 10% of the shelf space is residential, so they want to use the rest for businesses such as restaurants and hotels. There is already a strong colonisation of the riverbanks by hotel boats today.12

This is in fact a question of connecting not only the boats but the riverbanks themselves to sewers to develop profitable leisure activities, extending Paris’s development on the river. For houseboat owners, resisting these infrastructures therefore means resisting the transformation of the banks into yet another leisure and shopping pedestrian area in which they have little chance to stay in the long term.

The French association of boat owners (ADHF-F) and a local boat owners’ collective immediately protested against the authority’s demand, urging a refocus on ‘non-collective’ sanitation methods that would allow the boats to remain ‘off-grid’ in Paris. The first reason for boat owners to reject sewer connection was the extent of the works to be carried out on the boats. Because the boats are located lower than ground level and lower than the sewers, their connection system must include a pipe network to collect all wastewater at the same point, a lift pump and non-return valves that prevent water from the sewers from draining into the boat by gravity. The installation of these systems is costly for boat owners, but their main concern was sewage flowing back into the boat in the event of a pump malfunction, frost in the connection hoses or a river flood. Some of them refused to equate their boats with buildings built on land because boats, by their nature, cannot rely on gravity to avoid wastewater reflux problems:

We end up with people (HAROPA) who think they know everything because they manage the river. They surely manage it financially, but they don’t seem to know what a boat is. We have had so many ridiculous discussions with them. They don’t get what the possibility of wastewater reflux means for us. The boat is our home, and no double-check valve is a hundred percent reliable.13

Finally, the ADHF-F insisted that connecting the boats to the sewerage network contradicted the basic tenet of boat-based housing, which is its autonomy vis-à-vis the ‘people of the land’. The idea of technological autonomy, of a symbolic and material removal from urban infrastructure, is central for many individuals or communities who choose off-grid lifestyles (Vannini and Thaggart 2015). Bringing forth images of both the vulnerability of the floating habitat (which can sink) and the freedom it affords to its inhabitants (who can, in principle, move their boat to a different location if they want to), they insisted that boats should remain independent from a fixed drain and rely on autonomous sanitation techniques instead. Among these alternatives were compost toilets – dry toilets that create compost from faeces.

From hydrophilic to edaphic socio-microbial alliances

Compost toilets were first implemented in the context of remote premises, inhabited by communities that voluntarily extricated themselves from the grid and the grip of public authorities. They have been seen as a device that allows ‘disconnection from the State and reconnection with the local environment’ (Pickering 2010). Compost toilets function without a water flush. Excreta is received in a bin where they can be covered with wood shavings to avoid the smell and start a composting process. When urine and faeces are collected separately, the latter can be dried by a ventilation system, and the former treated apart. In composting, the excreta are brought into contact with plant litter and living organisms (bacteria, fungi, multiple invertebrates), under specific aeration and humidity conditions.14 These soil-related bacteria and other organisms digest the material and the rise in temperature finally eliminates pathogens, making composting a low-tech, versatile form of edaphic (related to soil organisms, from Ancient Greek édaphos, ‘ground’) sanitation technique.

In recent years, the ADHF-F has come to view compost toilets (or dry toilets) as a technique that could allow houseboats to continue to eject urine and grey water (from cooking, showers and laundry) with a light treatment, so that they need ‘only’ treat faeces, which concentrate the bacterial problem. Nevertheless, beyond its alleged legality, the practice of dry toilets on board a boat still raises many questions, both practical and regulatory. In 2019, the ADHF-F therefore approached the French Network of Ecological Sanitation (RAE)15 with a view to conducting a study on dry toilet systems associated with the treatment of grey water by floating phyto-purification. The study demonstrated that it was technically and legally possible to install a composting box on the deck of a boat, as long as the floor is made sufficiently waterproof so there is no leak into the boat. Nevertheless, the barge dwellers whose practices were documented in the framework of our investigation16 do not, in general, compost individually on board but on the quay near their boat or in a shared garden near the port. These are collective composters that can accommodate dry toilet materials and vegetable waste. Alternating between toilet waste and vegetable waste, from a kitchen or a garden, ensures efficient fermentation. On a boat taken alone, these conditions are difficult to achieve, as one boat owner explained to us:

I have installed urine diversion dry toilets. I compost the solid part on the deck. I am the only one around here with dry toilets, but all the other boat owners in the area bring me their organic matter. I would not have enough material to be able to compost otherwise.17

These systems of pooling materials offer a middle ground solution, but they are currently prohibited by a 2009 decree on Non-Collective Sanitation, which states that composting one’s faeces is only legal in one’s own garden or basement – a limitation that is not specific to houseboats but can concern any building in densely populated urban areas. The ADHF-F and the RAE therefore began to consider setting up a comprehensive toilet waste management coordination plan for compost toilets, including the organisation of waste collection by a specialised service equipped with ad-hoc toilet drainers, the delivery of these materials to a local composting platform in the suburbs, and identifying prospects for the resulting compost.18 Even though it is currently more a promise than an operational solution, this last option generates significant enthusiasm among some boat owners, who see it as an opportunity to contribute to a new kind of sanitation network not based on a confined water stream but rather on soil processes.

As we conclude this chapter, we can only speculate about the future of the alliance between the boat owners and the RAE, and about the establishment of a new pathway for collective toilet composting. However, the current discussions are already generating new socio-microbiological assemblages – at least in the technical hopes and imagination that inform these debates. Even though most boat owners are mainly concerned with the risk of a sewer overflow for their own boat, the involvement of the RAE goes some way towards reframing the controversy at a new level: that of the poor environmental value of conventional sanitation systems.

These emerging edaphic socio-microbiological assemblages can be linked to the wider features of ecological sanitation as described by Gay Hawkins’s work on its development in Australia. This movement revolves around a critique of mainstream sanitation systems, described as ‘magical invisibilisation devices’ that allow city dwellers to turn a blind eye to the issue of what becomes of their excreta as they – the excreta – become confined in water and pipes situated underground (Hawkins 2004). By comparison, these movements promote the creation of a distributed treatment and evacuation pathway (that treats excreta in multiple composting boxes situated above the surface) as a revolutionary approach to sanitation, one that does not aspire to simply get rid of unwanted organisms by sending them away in the evacuation stream but tackles the problem of faecal contamination ‘at the source’ (Legrand 2020). Unlike water, soil does not flow in pipes or over pavements. It stays still, at least apparently, and invites urban communities to become concerned again about the question of human excrement (also called ‘night soil’), its circulation and its transformations. In these discourses, on-board dry toilet systems appear as a way of countering not only conventional sanitation’s exclusive reliance on the aquatic environment as the key agent of sanitation but also the centralising impetus of water engineers, making soil-based sanitation methods appear as a key step in reclaiming ‘responsibility’ for the becoming of one’s ‘shit’ and its microbial content (Hawkins 2002).


In following the growing topic of open water bathing in urban rivers, this chapter has led us to analyse the changing microbiopolitics (Paxson 2008) of excreta surrounding the emergence of faecal bacteria as an indicator in river health monitoring. With regard to general environmental regulations of water quality, before the 2024 Olympic Games project the presence of faecal microorganisms in the River Seine was not regarded as a relevant criterion in assessing its environmental quality. Once the new horizon of making the Seine legally bathable envisioned putting human bodies in contact with the river water, microbiological presence, through sentinel species such as E. coli, gradually became a matter of concern. This attracted public attention towards the breaches and leaks in the sanitation system and led to the mobilisation of new political and technical actors, some gathered in commissions such as the Bathing Committee, others that represented new disciplines, such as water ecologists, but also unexpected actors such as the Port of Paris, wild swimmers and a collective of houseboat owners who objected to being entangled within the reticular wastewater system, instead advocating ‘on-board sanitation systems’.

We showed that the controversy over houseboat sanitation issues, although a minor event on the scale of the river and of Paris, changed the way human-microbe relationships were framed in discussions on the clean-up of the river. Whereas the general objective of making the Seine bathable changed the discourse of water sanitation from water ecological quality criteria to discussions over the presence of pathogens harmful to human bodies, the boat sanitation issue brought up larger questions of which microbial communities – soil microbes or water microbes – were to be enrolled in techniques of human waste management, and of how new socio-microbial alliances can be forged in the hope of making the becoming of excreta public. On top of the classical anthropological question of what is understood as contamination or pollution in regard to cultural purity standards (Douglas 1966), or that of how the governance of social life interlinks with that of microbial life, this case shows how human bodies and microbes come to participate actively in multiple arrangements of knowledge, governance and regulation that always redefine what they are and why they matter, but never quite manage to stabilise them in controllable entities.


1 Interviews with local officials, sanitation engineers, researchers and instructors, as well as houseboat owners and their representatives, were conducted by Marine Legrand during spring and summer 2020, completed by a series of observations during public conferences.

2 Interview with Fabien Esculier, in charge of a research programme on the ecological transition of sanitation, former head of the ‘Seine water basin police’ service.

3 Interview with F. Esculier.

4 Interview with Miguel Guillon-Ritz, member of Water and Sanitation Technical Department (STEA) of the city of Paris.

7 Interview with Étienne Doumazane, sanitation instructor.

8 Interview with F. Esculier.

9 Orient and Artelia, Missions d’assistance technique relatives aux infrastructures gérées par la direction de la propreté et de l’eau, Ville de Paris (2019).

10 SEPIA Conseil, Étude de l’assainissement des bateaux-logements (2007). Today, the official sanitation solution for boats is the storage of raw sewage to be emptied at the quayside. It is not applied in practice due to the lack of adapted equipment in ports.

11 ADHF-F General Assembly report, 26/01/19.

12 Interview with Raphaël Colette, vice-president of the ADHF-F.

13 Interview with R. Colette.

14 Time is also key in the process: at the domestic level, the WHO recommends a composting time of two years before possible use in agriculture (WHO 2012).

15 The RAE is an association which advocates for decentralised forms of sanitation that protect aquatic environments and return the fertilising resources contained in human excreta to cultivated soils. It gathers together firms, associations and individuals who practise and advocate for the use of dry toilets and phyto-purification in various contexts, including cities.

16 In Paris and Toulouse agglomerations.

17 Interview with R. Colette.

18 RAE, projet d’assainissement écologique pour habitat flottant (2019).


We thank Charlotte Brives, Salla Sariola, Matthäus Rest, Denis Chartier, Sandra Fernandez and Marc Higgin for their comments on earlier versions of this chapter.


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