When The Grid Is Too Far Away: A Systems Approach To Managing Rural On-Site Wastewater Plants In Norway


  • In Norway, on-site wastewater treatment systems often fail to meet their target treatment levels.
  • A range of actors are involved in the management of the plants, with few incentives to improve performance.
  • A systems-approach can improve compliance by improving agency and accountability amongst the actors involved.

On-site wastewater treatment systems (OWTS) are proposed as a one-stop solution in rural and sparsely populated areas not served by municipal sewage systems. In Norway, uptake of OWTS is fuelled by several processes: rising affluence drives a rapid growth in vacation homes with piped water supply; old septic tanks are due to be replaced; and stricter environmental regulations require a higher level of treatment. Despite the increasing prevalence of OWTS, many plants fail to meet their legally mandated treatment levels, releasing poorly treated effluents to rivers and lakes. In this piece, I present how one agency applies a systems-approach to tackle the issues of managing OWTS. I will begin by explaining the growth and limitations of OWTS in Norway, before presenting the web of actors involved and finally discussing the work done by one agency to address these issues.

Tilsynskontoret for små avløpsanlegg i Lier (The regulatory agency for small sewerage systems in Lier), hereafter referred to as Tilsynet, was established in 2011 after nine municipalities west of Oslo joined forces to tackle water pollution. Tilsynet currently regulates more than five hundred OWTS. Additionally, it serves 12,000 properties with septic tanks, with the majority more than 30 years old. It is therefore likely that the number of OWTS will increase rapidly over the following years, making it vital to establish mechanisms to ensure these plants meet their targeted treatment levels.

The terminology around septic systems can be confounding. In this post, I distinguish between septic tanks and OWTS. Septic tanks separate and settle faecal sludge, before releasing the remaining liquid to surrounding soils or waterbodies. OWTS require one or more additional treatment processes, typically biological treatment through aerobic and anaerobic processes, chemical deposition of phosphorus as well as UV treatment, filtering or chemical treatment for intestinal bacteria.  

Illustration of a dual-chamber septic tank. Source: EPA
An example of an OWTS featuring aerobic treatment. Most systems in Norway are required to have additional treatment with chemical phosphorus deposition before release to soils. Source: EPA

While low installation and maintenance costs make septic tanks the preferred solution, there are a range of reasons why OWTS might be required. Septic tanks are unsuitable in areas with poor soil depth, permeability and infiltration capacity, which limits the treatment capacity in the soils. Furthermore, the risk of polluting drinking water due to insufficient distance to groundwater, wells or waterbodies will mandate higher levels of treatment.

For OWTS to be certified for use in most parts of Norway, the system must reduce biological oxygen demand and phosphorus concentrations by at least 90 percent. Some municipalities also require the concentration of intestinal bacteria to meet the requirements for bathing waters (1000 bacteria per 100 ml). These tests are run in ideal conditions by an independent body (SINTEF), and there is increasing evidence that many systems fail to meet their targets over time. This is particularly the case when not properly maintained and serviced. For instance, in the municipalities regulated by Tilsynet, only one third of plants met the required treatment levels for all parameters in 2018/2019.

Results from Tilsynet’s biannual tests. The lack of improvement over time is partially attributed to an increasing number of OWTS being tested. Source: Tilynets annual report (in Norwegian).

There is a surprisingly large number of actors involved in the management of OWTS in Norway. Prior to construction, the owner must obtain a pollution permit from Tilsynet, depending on a technical consultant to design the system. After construction, the owner of the system is legally responsible for its functioning and is held financially accountable if the system fails to adequately treat the effluent. However, OWTS are complicated affairs, and therefore the owner must have a contract with a certified serviceperson who de-facto runs the plant. The service person is usually affiliated with a particular brand of OWTS, servicing all of their plants in the area, which means the owner cannot change their service technician if they are unhappy with the service provided.

The web of actors involved in the day-to-day management of OWTS.

Furthermore, the OWTS is emptied annually by sludge collectors and Tilsynet biannually inspects the plant. The inspection entails sampling the treated water and checking the functioning of the plant. Finally, the local municipal government, the county governor and national government all influence the legal and financial environment in the which the regulatory body acts. 

Tilsynet has since its foundation in 2011 found that simple inspections and feedback to owners have not had the intended effect. Treatment quality has remained poor over the past decade, and as a result, Tilsynet is increasingly implementing a systems-approach to regulate the plants. This entails a range of initiatives to improve dialogue and capacity amongst the actors involved. The aim is to increase the sense of responsibility and agency of all stakeholders, ranging from homeowners to service technicians and sludge collectors.

In practice, this means building dialogue with sludge collectors in order for them to report signs of malfunction, such as sludge overflows, foreign objects or leaks. This partnership contributes to earlier identification of acute pollution events, as well as increasing the awareness of homeowners, who are notified by Tilsynet of feedback from the sludge collectors.

To further raise awareness, Tilsynet sends reports from plant inspections to both homeowners and technicians. These reports stipulate the owners’ responsibility to order an extra service from their technician if the plant performs poorly. It also demands feedback from the technician on what actions have been made to improve the functioning of the plant. It is in this interaction that issues of incentives become apparent, as owners are incentivised to keep their plant operating well due to the risk of being fined for polluting. However, the service technicians are in practice rewarded for poor performance as they can charge for an extra service.

In order to tackle these disincentives, Tilsynet is working to shift incentives and build dialogue with service technicians. Tilsynet regularly conducts meetings with technicians as well as the companies they are affiliated with. These meetings aim to improve understanding of issues technicians face, in terms of their dialogue with plant owners, as well as making both producers of OWTS as well as technicians aware of their responsibilities as the managers of these plants.

To improve accountability and transparency in the market, Tilsynet publishes statistics on the performance of each brand and model of OWTS. By publicising this information, prospective buyers – who are penalised for poor performance – may get a better overview of which suppliers deliver on their commitments. This puts pressure on producers and technicians to adequately maintain plants and ensure they meet their legal requirements.

In conclusion, it is firmly established that unregulated OWTS are unlikely to comply with stringent environmental regulations and may not be the one-stop solution promised. This failure is due to the complex ecosystem of actors involved, with unclear divisions of responsibility and misplaced incentives. Over the past decade, Tilsynet has learnt that extensive oversight and involvement of all actors is vital for plant performance, even if progress is slow. Such a systems-approach improving agency and holding actors accountable is a promising way to address pollution from OWTS, and might be relevant for other governments seeking to tackle similar challenges. 

Idun works in the Norwegian public sector on flooding, sanitation and the water environment. She holds an MSc in Water Science, Policy and Management from the University of Oxford and an MA in Sustainable Development. 

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