At the turn of the 20th century, a very small share of the rural population had piped water and/or wastewater or WC. Latrines were emptied on the dunghill together with animal excrements and spread on the farmland. Water, mainly for cooking purposes, was carried into the houses and wastewater was carried out and thrown in gardens or into the nearest ditch. In terms of nutrient recovery and cycling, this system was likely to have been very efficient. The application of this solution started to change after a few decades into the century and by the early 1940s about a third of the rural population had piped water and wastewater [19]. However, only around five per cent had bathroom and WC installed suggesting that the nutrient-rich fraction of the sewage was handled the traditional way.

In order to understand these developments we have to go back to the major transformation of the urban handling of water, wastewater, and sewage starting in the second half of the 19th century when the city populations grew. The cities of the time experienced recurring epidemics of, e.g., cholera, because of their rudimentary handling of wastes in general [20], and sewage in particular [21]. Cities started to install water pipes to improve the situation regarding polluted wells. Different systems for handling the excreta were tested with the purpose of improving hygienic conditions and pleasantness of urban living. The bucket system implied that, e.g., farmers in the periphery of the cities transported and got rid of buckets of excreta in different ways. In the second half of the 19th century a system for fertilizer production using excreta and chalk was operating in Gothenburg (production of so called poudrettes), but this system did not become the large-scale solution for the 20th century [20]. In order to promote change, the government instituted the Health Protection Regulation in the 1870s, which regulated the construction of toilets, the handling of sewage and latrines. At the end of the 19th century water and wastewater pipes were installed and water toilets were applied on a larger scale. The situation improved drastically with regard to hygiene. A few decades into the 20th century 90% of the urban households were connected to water and wastewater systems, of which a majority had WCs [19].

Compared to the situation in the cities the countryside was lagging behind. Even though the health situation and the occurrence of epidemics cannot have been as bad in the countryside as it was in the cities several decades earlier, there were certainly calls for action to relieve the people in the countryside from their poor living conditions [22]. The lifestyle of the rural population was not coming anywhere near to the modern lifestyle that the urban population enjoyed at the time [23]. However, since many people were poor and thus had other pressing problems to think of, at least initially they may not have perceived the benefits of piped water and the WC. Nevertheless, it is likely that a majority of the people very soon aspired to WCs, since they must have been perceived as a convenient alternative to the latrines [22,24]. On a national governmental level the issue of the neglected countryside was also acknowledged [25]. The steps taken already by the state to improve the living conditions in general, supporting the introduction of central heating and more spacious apartments, also came to include improvements to hygienic conditions. Thus, the idea of improved hygiene in countryside homes seems to originate to a large extent from the urban upper and middle classes who already were experiencing higher living conditions, although this with time probably also represented the views of many in the countryside.

To stimulate change the national government funded large-scale home improvement programs during the decades before and after World War II. One of the main purposes of the reforms of the 1940s was health promotion [6,26], emphasized by the fact that the main responsibility of inquiry and planning was at the Health Protection Agency [26]. A reason for initiating these programs was that the industry needed workers, and the state helped out by stimulating the building of homes closer to the industries and by promoting sound home environments. Taxes from workers in turn also gave the state revenues to spend on the reforms. The home improvement activities in themselves in addition created jobs. Although the programs focused on cities and population centers they also covered the countryside. In terms of stimulating change of water and sewage handling, it seems to have been particularly the government interventions after World War II that influenced the transformation to foremost piped water and wastewater. The subsidy programs for the installation of water and wastewater systems were relatively generous. Through the inquiry and proposition in 1942 home-owners could receive a subsidy of SEK 200—the costs of investing in piped water and wastewater ranged from SEK 210–865 [25]. The already existing municipal health protection committees came to administer the subsidies and loans linked to the general home improvement activities (in Swedish Allmänna bostadsförbättringsverksamheten), including the subsidies and loans for the installation of water wells and piped water and wastewater. The subsidy program was expanded in 1949, after an initiative of the Swedish National Institute for Public Health, which led to an increase in state funding of both urban and rural water and wastewater systems [26]. The following state inquiry into small-scale sewage systems (in Swedish 1950 års avloppsutredning) in 1944–1955 [27] resulted in further increased state-funding. During the second half of the 1950s, the state prioritized household connection to water and wastewater systems, either through local and individual solutions or cooperative or municipal solutions. Funding increased multi-fold, in the last three years of the decade from SEK 200–600 million [26]. The expansion of piped water and wastewater systems and WCs in the countryside homes was distinct during the late 1940s and the 1950s, as Figure 2 illustrates. About 250,000 water and wastewater systems and 200,000 WCs were installed in the countryside during this time period.

Other, landscape level, processes also had an influence on the transformation of OSSs. The urbanization “pull” of industrialization processes, providing opportunities for employment, as well as a combination of high rural nativity and limited agricultural land, implying a limited opportunity to earn a living from the land when the land was divided into smaller parcels, also “pushed” people from the countryside. This led to the abandoning of many countryside homes and also implied the end of old OSSs and traditional waste handling systems [28]. The emigrants from the countryside to the cities also very likely brought with them the lifestyles of the cities when they returned for visits, contributing to the change of norms regarding sanitary facilities. We speculate this contributed to the process of making WCs the desirable solution.

The OSS rules of the time did not spell out any constraints regarding how to arrange the handling of sewage in the countryside. In fact, already at this time the existing rules for handling wastewater, which in the countryside did not include sewage, did not seem to have any impact. The state inquiry of 1942 noted that the regulation from 1919 “does not appear to be effective” [25] in ensuring a good situation with regard to hygiene. In terms of wastewater treatment, discharging the wastewater to the nearest watercourse was considered sufficient. A suggested but rarely applied solution for further treatment when it was not economically reasonable, due to the distance, to discharge wastewater to watercourses, was to use bottomless sludge separators to “defuse the wastewater” [25]. Treatment systems, such as one- and two-chambered sludge separators, which existed at the time, were generally not an imposed requirement [25]. These types of OSSs were only considered necessary if a WC was installed and when wastewater was produced in more densely populated areas, i.e., in outskirts of cities and population centers or “row”-villages. From the state’s perspective a far-reaching introduction of WCs was at that time (1942) not seen as desirable in the countryside, foremost because of the benefits and lower health risks of the traditional way of using latrines and spreading excrements on farmland [25].

However, the distinct expansion of WCs into Swedish homes in the decade that followed, without subsequent treatment steps, gave rise to water pollution [27]. According to Rosén and Rosén [24] the experiences of the epidemics of 1946–1947 were important motivators for the stricter rules imposed in 1956, requiring three-chambered sludge separators, which improved the treatment of foremost pathogens. At this time the county administrations were given the authority to oversee the developments in the countryside. The changes in the 1958 health protection regulations implied requirements on a declaration before installing wastewater systems, and that the authorities thereby gained control already at the installation stage [6].

In summary, before the 1950s, sewage and wastewater handling was formally a largely unregulated area in the countryside. Tradition and local knowledge were used when building farm-level systems for handling water and latrines. The processes of changing the handling of water and sewage in the cities preceded a similar transformation in the countryside. Hygiene concerns, increased convenience for homeowners, and changed expectations regarding toilets, made the WC a desirable solution in the broader society and with time also in the countryside. The unspecific rules of the 1940s and 1950s created a space for action for individual homeowners and other actors having knowledge of how to install the systems. Further, in the absence of specific rules and enforcement capacity, it was possible for individual homeowners to install WCs, without much notice taken by the authorities. What, however, initiated technological change and what made WCs and water-based treatment systems take off? As described, actors from the established, primarily urban, sphere such as the media, middle-class citizens and others who had already experienced improved material welfare, and governmental agencies were in favor of making the countryside follow the example of the cities. At first, this was in conflict with the interest of the homeowners who did not seem to have seen the benefits. Homeowners could however not resist the thrusts, which came from many directions. However, homeowners must soon have realized the convenience that an indoor WC brought. Returnees, guests and others from the cities must have exerted pressure on the countryside residents and been an important carrier of technology expectations and norms from the cities. Once the rural homeowners adopted the new ideas, tensions were resolved and instead there was a relatively high coordination and alignment between activities and agendas of rural homeowners, governments, authorities, and established spheres. The government introduced rules that prescribed homeowners to have basic treatment in the form of a sludge separator when installing a WC. Local health protection committees were given the task of overseeing the implementation of these rules and an obligation for homeowners to apply for a permit to install an OSS gave the committees a means to do so. That way the role of local knowledge and traditions was replaced by the authorities’ knowledge and rules for structuring homeowners’ actions. The technology was also fairly rudimentary and while the installation of pipes required labor, the installation could be handled locally, without much assistance from trained contractors.

During this era, the decades after World War II, the government became a relatively stronger player, not least because of industrialization and the increasing tax revenues that followed. Due to a combination of the political climate and the economic capacity, governmental interventions were possible. Importantly, the government intervened and subsidized the construction of water and sewage handling systems in rural areas, giving homeowners the economic capacity to embrace the new technology. Homeowners and others in the countryside who may have objected to this development were not sufficiently large in number to bend the development path, e.g., the use of other technologies. Thus, when using Mahoney and Thelen’s theory of incremental change we interpret the quite abrupt technological-institutional change as being rooted in activities starting several decades before. Several actors used change strategies that served their own differing interests but despite this they all acted in ways that resulted in a coherent development of OSS. It was a combination of an enabling political context at the landscape level, self-motivated homeowners, and government interventions that led to the expansion of piped water, WCs, and the use of sludge separators as the principal treatment process in Swedish countryside homes. This implied the birth of a new socio-technical configuration [8] from the 1940s with piped water and WCs as dominant technologies. However, as WCs replaced latrines and only rudimentary technologies were applied, the nutrient capture capacity of OSSs decreased and nutrient loads increased drastically, as illustrated in Figure 1 (see Section 1).

The rapid expansion of water and wastewater systems in both the countryside and the cities made polluted water an increasingly pressing issue, now situated in a context of broader environmental concern. Until the 1960s the large majority of installed treatment systems in the countryside were using, at best, different variations of sludge separators with low nutrient retention capabilities. Concerns regarding environmental pollution led to the introduction of the environmental protection legislation (EPL: in Swedish Miljöskyddslagen) in 1969 and initiated the environmental management in Sweden [29]. The EPL restricted the emission of wastewater and also required permission for installation of sewage systems. According to Christensen [6], this implied that the burden-of-proof increased for the individual homeowner. Moreover, for the first time all homeowners were clearly covered by the legislation and not only homeowners who were setting up new sewage systems. Besides the introduction of EPL the control functions of authorities were strengthened and the municipalities were given the task to inspect OSSs, earlier done by the county administration. However, the local environmental authorities could only interfere when damage occurred that could be linked to an existing wastewater system.

With the new legislation of 1969 OSSs had to meet both environmental and health protection aims. The existing rules from 1962 implied that simpler types of infiltration beds were required besides sludge separators. These rules are in essence still valid [30] having been adjusted first in 1974 [31], and once again in 1987 [32], and with these stricter rules on construction, materials, and dimensioning, the nutrient capture capabilities of infiltration-based technologies was slowly improving.

One effect of the legislation was that new houses, permanent homes as well as summer homes, were equipped with infiltration-based treatment technologies. Many of today’s existing Swedish OSSs were installed during this and the previous period and are still in use [5]. In places where conditions did not allow infiltration, e.g., because of too fine or thin soils, or where the population density was high, such as in many summer home areas, closed tanks were a relatively common solution. However, the government’s efforts were not directed at the existing, and aging, OSSs, likely because there were other larger and more obvious sources of water pollution, such as the municipal wastewater treatment plants (WWTPs) and large paper and pulp industries that were largely lacking effective treatment steps at the beginning of the 1970s [7]. An indication of where the money flows were directed is that the government spent about 1.5 billion SEK on municipal WWTPs in the 1970s [7], while no corresponding effort was made directed at mitigating nutrient loads from OSSs.

Of relevance for the development of OSSs was also the phenomenon of Swedes obtaining summer homes, a trend taking place as people got more summer vacation and increased “consumption space” in the 1950s and the 1960s [33]. For instance, during the 1960s about 160,000 summer homes were built. In itself this change did not have much influence on environmental loads because of the relatively low utilization of the summer homes and the fact that many were constructed with latrines. However, since the 1960s mobility has increased due to development of the transportation system and cities have sprawled. Summer homes that were once perceived as located far from cities have become attractive to use as permanent homes. Demands for more comfortable living have grown stronger which have led to summer homes being equipped with piped water and WCs, and hence water-based treatment technologies. Further, in the cases where abandoned permanent homes were transformed to summer homes following the urbanization process of the 1940s to 1960s the existing system for handling sewage was in many cases the rudimentary handling systems applied up to the 1960s. The authorities did not neglect these developments. Already at the beginning of the 1970s, guidance was given regarding which technology to use in summer homes, favoring dry solutions [34]. Today 135,000 are equipped with urine separation technologies [35]. Towards the end of the 1970s there were also inquiries aimed at finding solutions to the issue of OSSs in summer homes in transition to permanent homes, e.g., [26,36,37]. In some contrast to this, in the cases where closed tanks have been used, the environmental loads have remained relatively low since the sewage has been collected and transported to the municipal WWTPs, which have seen increasing nutrient removal capacities since the 1960s and particularly from the 1970s [7].

In summary, the 1960s and 1970s were marked by growing environmental concerns that translated into governmental action and further institutional arrangements and regulation of wastewater. The rules regarding the application of especially new OSSs came to embrace both health and environmental concerns. From a technical and environmental perspective these changes explain the break around 1975 of the negative trend for nutrient removal capacity, as Figure 3 shows. An important technical factor is also that municipal WWTPs have shown increasing nutrient capture rates since the 1970s. Since the sewage collected from closed tanks and treated at the municipal WWTPs is a relatively common solution this may have influenced the overall nutrient capture capability of OSSs.

However, several circumstances made the long-term environmental gains rather small. Homeowners could continue to use more rudimentary treatment technologies since they were not subjected to inspection. The technical lifetime of the dominant technology (sludge separator combined with an infiltration bed or compact filter) was unknown at the time of installation and has been shown to be limited, cf. [16,38]. Further, WCs replaced latrines in rural and in summer home areas on an increasing scale, creating conditions that were difficult for municipalities and environmental protection authorities to address. This last factor implied that landscape-level processes, in this case the broad transformation of summer homes to permanent homes as part of sprawling cities and changed user demands, gave rise to changes in some of the elements at the regime level even though the result was not a complete change of existing OSSs, nor did the new technologies diffuse beyond their initial niches. For instance, closed tanks did not replace existing OSSs and even though urine separation technologies have become common in summer homes [35], this technology has not made it beyond this niche to permanent homes [5].

The origin of the technology-specific rules was the increasing knowledge about environmental impacts, discoveries of water quality problems, and rising environmental concerns when scientific knowledge became accepted on a broader scale. The 1960s to the 1990s was a period where national government strengthened environmental institutions, introduced more specific laws, and strengthened enforcement capacity by creating local public health and environmental protection authorities. The technology-specific rules gave certain actors, e.g., those producing components and installing sludge separators, a position to act while restricting the room for action of other potential suppliers. For most users the change in treatment technology did not create any tensions with their expectations or daily routines involving the technology. The “interface” (the tap, the WC etc.) to the sewage handling system remained essentially the same, at least in the cases of newly constructed houses. In cases where the change of technology implied a changed “user interface”, most prominently when latrines were turned into WCs, this was in line with users’ expectations of the new technology and implied, as desired, more convenient systems. In both cases it was in the interest of homeowners to install these specific technologies, that is, piped water, WC, and further means of getting rid of the wastewater from the lot. From this perspective it is also logical that there was no major state aid aimed at easing investments in OSSs similar to the previous decades—it was not needed because of strong user desires for WCs.

Compared to the previous period, which was marked by reconfiguration of many system elements and much activity on several administrative levels, the period from the 1960s and onwards is marked by stability. Technological changes occurred not on the large-scale but in pockets, i.e., when summer homes were built or when summer homes were transformed to permanent homes. Though environmental concerns grew in society this did not lead to major technological changes. The treatment technologies applied remained essentially the same, based on the WC and sludge separators, and were not changing very much during the period besides slight changes in the dimensioning of treatment system components. The ST system and institutional elements therefore followed a path defined by the application of certain types of treatment technologies, which were embedded in a configuration including users’ expectations and routines, and formal rules and guidance that defined appropriate treatment technologies. The institutions that were built-up during the period and the rules that were applied were continuously built on the previous ones—new structures were layered [11] on previous ones and did not imply tensions between, e.g., actors or other aspects of the socio-technical system. Also, the institution-building activities were directed at other sources to the nutrient load problem, unintentionally reducing the interest in OSS and not focusing on efforts such as enforcement capacity-building that could have altered the development path for OSS. Therefore, despite a growing concern for the environmental impact of wastewater and incremental institutional changes, environmental outcomes did not improve correspondingly.

In the 1980s and the 1990s concerns for the environment increased, e.g., as resource and pollution problems were increasingly discussed, cf. [39]. To cycle nutrients, including those from the sewage, became increasingly important at the political level, even though it had been highlighted already in the early 20th century [20,21]. Also, after the Rio UNCED conference in 1992 there was an emphasis on making people more involved in environmental management, in line with the ideas of Agenda 21. As a response to the Waste Water Directive, inspection campaigns were run in the 1990s. There is anecdotal evidence of inspection campaigns in several municipalities along the Swedish east coast, using informative means of persuasion, which had poor effect in terms of homeowners improving their OSS [40]. One of the reasons was the limited judicial possibility to prescribe homeowners to change malfunctioning OSSs, which was in contrast to the possibilities when new houses were constructed. The transformation of summer homes to permanent homes also continued during this period. Until the 1990s, basically the same treatment technologies were required [31,32]. Some municipalities introduced local building regulations that restricted homeowners to only apply OSS techniques that enabled nutrient cycling when constructing new houses [41]. This implied that some type of composting toilet or urine separation system was the only technology allowed. Another local building regulation was the ban against closed tanks imposed on homeowners renovating or building new houses [42].

The difficulties in implementing the OSS legislation were acknowledged by the national government who took measure through the environmental code (EC: in Swedish Miljöbalken) that came into force in 1999, gathering most of the existing environmental legislation applicable to wastewater systems, cf. [6]. Importantly, the code emphasized the function of OSSs in terms of, e.g., their nutrient capture capability instead of a prescribed required technology. Further, the EC stipulated that sustainable development aspects, including nutrient cycling should determine protection levels that in turn influenced the requested degree of treatment. Importantly, the EC made it possible to place injunctions on all homeowners with existing OSS (i.e., not only in cases where new houses were built) to change the system. The code also emphasized the consideration of national environmental goals, adjacent regulatory structures, and agreements decided on an international level, including the consideration of Natura 2000 areas, and to include goals in accordance with the Water Framework Directive and the Baltic Sea Action Plan in the inspection practice. Christensen [6] suggests that the new EC enables local health and environmental protection authorities (HEPA) to place stricter requirements than the earlier legislation. From the new code, guidance was developed in 2006 [43] suggesting two levels of environmental protection depending on the sensitivity of the recipient waters and associated nutrient capture norms, where the higher level of protection implies stricter requirements than ever before. In practice, the implication of a high level of environmental protection is that sludge separators with subsequent infiltration or filter beds are no longer an acceptable solution. Consequently, specific technology is not prescribed any more, since the minimum requirement is determined by the sensitivity of the nearby environment. However, there is room for deviations since the HEPA is to balance the more far-reaching intentions of the regulations, i.e., meeting targets set on national and international levels, with reasonableness of the consequences for individual homeowners. The government introduced a tax reduction in 2009 as a subsidy to support homeowners refurbishing their houses [44]. This tax reduction halves the labor cost and if applied to an improvement of an OSS a total cost reduction of approximately 10%–30% is achieved (which is less than the subsidies in the 1940s and 1950s).

The emphasis on the technology-neutral “function” of OSS instead of specifying a minimum required technology is important since it opened up a variety of technical solutions that fulfill the specified function. Thus, if rules can be flexibly interpreted this gives actors more room to act, both in line with the intentions of the rules but also beyond the original intentions. Certainly, there was technological development already in the 1960s towards more advanced treatment systems and the modern type of compact treatment plants came in the late 1980s [45]. However, other technologies than the minimum required technology specified through the regulation were still not applied on a large scale [5]. The legislation from 1969 prescribed treatment corresponding to more far-reaching treatment than a three-chambered sludge separator, which in practice implied septic tank systems—a three-chambered sludge separator combined with soil infiltration or compact filter. Several factors can explain the changed legislation. The limited success of previous legislation in terms of improved OSSs, which was apparent since at least the late 1970s but certainly in the early 1990s [36,37,46], was likely also a driving force for the government to make a change in the regulations “to try something new”. The emphasis on technology-neutrality is certainly aligned with an ideological move towards a preference for market solutions, relying more on private initiatives and less on state interference. Importantly, the emphasis on function is also aligned with one of the institutional building blocks of the European Union, the EU Single Market Act, which came into force in 1993. The latter brings several factors that were not previously affecting the institutional development and adoption of various treatment technologies, when companies can act across national borders. Furthermore the inclusion of the CE conformity marking, containing a material performance declaration, nowadays clearly influences the institutional development in the case of the Swedish OSS [47].

During the 2000s the activities of local environmental authorities have certainly increased, and a majority of the municipalities have inspected OSSs to some extent [5]. However, the rate of inspections has been deemed insufficient compared to the large number of homeowners who need to improve their systems [48]. With the current pace of inspection in Sweden it would take about 80 years just to change currently deficient OSSs [49]. Until year 2000 few homeowners with an existing OSS were forced to change the OSS and did not do so, as evidenced by today’s large share of the technologies that were dominant already in the 1940s–1970s [5]. Furthermore, a majority of the systems installed after the 1960s have a decreasing treatment function with time, which adds to their poor environmental performance, cf. [38]. In the wider system there has also been increased activity, in that companies have entered the market with new products and gained market shares in the last 10–20 years [50,51]. Further, associations have been formed to capture the interests of different OSS actors, such as compact treatment plant manufacturers and installers (backhoe operators). Municipalities formed the national network Avloppsguiden in 2004 to support rule enforcement and harmonization of the requirements imposed on homeowners between municipalities. This network has with time also evolved to support homeowners in choosing OSS, and the entrepreneurs installing OSS.

In summary, from around the 1990s to the 2010s a set of changes in the character of institutions, as well as in the political context changed the rules of the game. Changes in market institutions (e.g., EU Single Market Act and national adaptations) make it possible for actors who operate across national boundaries to attract resources and use their position on one market when entering another market. This is certainly the case for many treatment system manufacturers for which Sweden is not their biggest market [51]. This institutional change which was external to the OSS regime reduced the possibility of keeping the previous technology-specific rules. By merging functional requirements with previous legislation and using the existing HEPAs to enforce the new legislation, the government could avoid the tension with the new market institutions and still keep, in principle, a high ambition level concerning environmental sustainability. Thus, in principle, the legislation changes gave the HEPAs power to judge the legality of the growing number of technologies on the market and to check that all homeowners continuously have well-functioning OSS. At the same time, the new legislation was not followed by more resources given to the HEPAs. The focus on environmental sustainability made some municipalities promote nutrient cycling systems in new permanent homes. Overall, the enforcement actions have been limited.