About 2,500 municipal wastewater treatment plants have been built in Norway, 400 of which have discharge permits from the County Governors. The municipalities themselves are responsible authorities for the rest, that is to say for populated areas of fewer than 2,000 person equivalents in the case of discharge to fresh water and fjord outlets, and of fewer than 10,000 for discharge into fjords and coastal waters. There are also about 350,000 treatment plants for approximately 800,000 people who either live in sparsely populated areas or have cabins. For these too, the municipality is the pollution control authority. Most wasteater treatment plants in Norway were built during the period 1970 to 1985. There are still about 500 untreated discharges, covering approximately 350,000 persons, where treatment plants have yet to be built. Two trends are that new treatment systems are being built for individual houses and cabins, while other buildings are being connected to the public sewerage system and closing down their separate treatment plants.
Treatment plants that discharge into fresh water, river mouths and some fjords have been constructed to remove phosphorus and often also organic material. These are known as advanced treatment. The phosphorus is removed to prevent algal blooms and the organic material is removed to prevent oxygen depletion. In more open coastal waters, mechanical treatment is more common, since the aquatic environment there is less sensitive to this type of discharge. These are screens, sieves or septic tanks and remove what would otherwise have been visible pollution and prevent the build up of sediments near the discharge points.
Even though 90-95% of the bacteria concentration is removed in advanced treatment plants, the remaing is still considerable.
The pollution retained by the treatment plants is called sewage sludge. This is an organic mass that is dewatered and mainly used as a soil improving agent in agriculture, parks, road embankments, etc. Because of the effective control of what can be discharged into Norway's sewers, the environmental toxin content of sludge is generally low, which means that soil nutrients can be recycled.
What is shown under wastewater treatment plants
Discharge data is presented for more than 700 advanced treatment plants, that is to say all the larger treatment plants that have been built to remove phosphorous and in many cases also organic materials. Many of these plants also measure the discharge of suspended solid (SS) particles and some heavy metals. All the figures are for the quantity of discharges per year and are based on 6 to 24 samples per plant. For each plant, it is also possible to link to discharge permits and summaries of inspections and controls that have been performed by the pollution control authority. It is also possible to compare individual treatment plants with others in the region. Most treatment plants are owned and operated by the municipalities or inter-municipal companies, and the municipalities are also the pollution control authorities for the smaller plants.
What is not shown under wastewater treatment plants
There are many more treatment plants in Norway than the ones that are accessible here, but those not shown are mainly mechanical plants that remove particles more or less effectively and have been built to prevent the build up of sediment deposits near the discharge points. Companies that have their own treatment plants for the discharges to wastewater from their industrial processes are not included in this overview. You will find these under "land-based industry".
The information found here is based on the data sent by the municipalities to Statistics Norway each year. Statistics Norway and the environmental department of the County Governors' offices perform a quality control and correct the figures if needed, based on contact with the local authorities. Where important data may be missing, Statistics Norway inserts standard values, so that national summaries of discharges can be compiled. There are some treatment plants that do not report data and as this summary cannot be subject to total quality control, the combined discharges will seemingly vary somewhat more than the actual discharges do. Work is constantly going on to improve this situation, so that in the course of time the picture will be complete and based on actual measurement data. Statistics Norway publishes discharge data every year, based on the same information from the municipalities.
When is new data presented?
This summary is updated every autumn, based on the municipalities submitting their basic data on 1 March and data quality being checked before publication.