Municipal wastewater sector - KOSTRA
Key figures are published annually in connection with Municipal-State-Reporting (KOSTRA) on the 15th of Mars (unrevised) and 15th of June (revised).
The figures are published on national and regional (municipal and county) level, in addition to grouped in economically comparable groups (see chapter 4.2).
220 - Division for Environmental Statistics
Data are collected by Statistics Norway on behalf of the Norwegian Pollution Authority with legal basis in the Pollution Control Act (13th Mars, 1981, no. 6). Statistics Norway can make use of the collected data for official statistical purposes with legal basis in the Statistics Act (16th June 1989, no. 54, §2-2).
Not relevant.
Not relevant.
KOSTRA started up as a project in 1995 with the intention to provide relevant and up-to-date information about resources spent, priorities and meeting targets in municipalities and counties. The goal is to collect data in a co-ordinated way, and make the information flow a one time delivery per year for all steering-information needed by municipality. The number of municipalities and counties was gradually increased until the reporting year of 2001, then all municipalities were included in the KOSTRA.
The KOSTRA waste water statistics provide information about number of wastewater plants, treatment capacity, type of treatment, degree of people connected, sludge disposal etc. The economical figures in intend to illustrate, on a municipal level, the relationship between revenues from wastewater fees, annual costs, and wastewater tariff, and provide national figures for the financial situation in the sector e.g. investments, costs and revenues.
KOSTRA provide steering information about municipalities and counties to the different interest groups, inhabitants, media, the municipality itself, different state organs and controlling authorities etc.
All municipalities in Norway (complete collection).
The Municipal-State-Reporting system (KOSTRA).
Not relevant.
Data is collected electronically once every year, and the information should be in hands of Statistics Norway by 15th of February.
The electronic forms contain built-in consistency checks and logical tests. When the data arrive Statistics Norway, they will be checked automatically and manually.
Unrevised data will be published on 15th of Mars. There is a second deadline on the 15th of April for municipalities to correct possible errors in the figures just published. The data is also revised by Statistics Norway.
The KOSTRA control and revision process is constantly adjusted and developed. A computer application named GENREV was introduced in 2002. The application has been updated in accordance with changes in the electronic forms.
Data are being published on different levels, as basic data and key figures. Basic data is generally reported in absolute numbers, and will largely constitute aggregated numbers summed up for a certain period of time or at a time of year. Key figures on the other hand are commonly a ratio (made up of different basic data). Key figures also contain various averages e.g. on municipal groups, county level and the whole country. A weighted average has been applied for most of the key figures. Absolute key figures are shown with arithmetic average (not weighted). Yes and no key figures have no averages. National averages are provided with and without Oslo. The data for Oslo is not always comparable with other municipalities.
Calculation of load
Due to the fact that only a minority of wastewater facilities undertake direct measures of pollution load, standard factors needs to be incorporated in the calculations. Thus, total load figures of phosphorus are largely based on this set of factors (see below for further details).
The following calculation procedure has been applied to municipal wastewater facilities, capacity of 50 pe or more, (Statistics Norway 20021):
1. If the wastewater facility provides information on load, expressed as kilogram per year, this information will be used directly.
2. If the wastewater facility provides no information, as specified in number point 1 above, but given outflow concentrations and average water quantities, then load is calculated in kilos per year from the following equation:
concentration (mg/l) x average water quantity (m3/day) x 365 / 1000
3. If measurements are not carried out, total load are calculated by multiplying the number of people connected to wastewater facilities with standard factors of average load per person per day (1.6 gram phosphorous per person per day):
number of people connected x 1.6 (g P/ day x person) x 365 / 1000
1Statistics Norway (2002): Discharges and treatment in the municipal wastewater sector 2000. Official Statistics of Norway, C707. Updated version (Norwegian only): Statistics Norway (2009): Utslipp, rensing og slamdisponering i den kommunale avløpssektoren 2007, D414.
Calculation of use of sewage sludge
2005 and 2006 data were reported based on gross sewage sludge and its associated percentage dry weight is now included in the reporting. In all other years dry weight of sewage sludge has been asked for. But in order to calculate the dry weight in 2005 and 2006, the information of percentage dry weight was essential, and in cases where percentage dry weight was missing, then the following method was applied to the data:
1. If percentage dry weight of the produced sludge product was reported, but not for the amounts of sludge used, then this percentage was then applied.
2. If percentage dry weight of neither the produced sludge product nor the amounts used was reported, a standard factor of 25 per cent dry weight was applied.
Calculation of age of the municipal wastewater pipelines
Calculations of the age of municipal wastewater pipelines on country level in the article - Todays Statistics - has been adjusted for pipelines of unknown age (not specified time period). Pipelines in these cases has been spread accordingly over the following time periods (1) before 1940, (2) 1940-59, (3) 1960-79 and (4) 1980 with the following percental distribution 50, 20, 20 og 10. In addition, the age presented in the article has in for some municipalities been imputated with data from earlier years if data was not avaliable from last year. These corrections constitute a few small excemptions, while the age figures in Statbank has not been corrected in this way (based solely on last years reporting and on the part of the pipelines which can be pinned down to one spesific time period).
Not relevant.
The 431 municipalities are grouped according to population and economic comparable groups. This is based on the report (in Norwegian only) Gruppering av kommunar etter folkemengde og økonomiske rammevilkår 2003. Rapport 2006/8, Statistisk sentralbyrå
The error-controls built in the electronic forms and at forms-delivery in Statistics Norway provide an automatic feedback to the reporting municipality. Experiences show that this reduce the level of errors compared to the earlier paper-based forms.
Some uncertainty is due to the measurements undertaken by the treatment plants; the level of accuracy may vary. Overall, the measurements undertaken in on North Sea counties are generally more accurate compared to the rest of the country. The reason is more stringent regulations and pollution ceilings for this particular area.
The highest level of uncertainty is associated with possible errors and incomplete data sets as provided by the municipalities. Information on various wastewater plants and municipalities is missing, and it is sometimes difficult to detect and correct all errors or inconsistencies in the reported data set. Some uncertainty is also associated with start-up year, capacity enlargement/reduction and closing down of certain plants, which again may affect the quality of aggregated county figures. This leads to uncertainty whether the wastewater plants are still running.
Non-reporting of wastewater plants or specific parameters can lead to uncertainty in the final statistics. In certain cases, a wastewater plant not being reported can mean that the plant is closed down or that is still running but has not been reported. Therefore, continuous effort is put into removing plants shut down from the statistics in addition to adding plants that is still running but has not been reported in KOSTRA like they should.
In order to lessen the burden of reporting, a few municipalities have increased the 50 pe reporting target to 70 pe. This problem however, is not expected to affect the total discharge figures.
Not relevant.
Possible errors may occur during the revision process. It is a necessary quality-assuring tool, but errors and uncertainty may also arise as part of the process. In particular, this applies to instances where previously reported material is used as substitute for non-reported data in the current year, but also other alterations to the material during the process.
The statistics of individual wastewater treatment plants (less than 50 pe) is often less certain compared to wastewater treatment plants equal to or larger than 50 pe.
Due to the fact that various well-established wastewater plants have not entered the database before more recent years, comparison over time may be limited. This applies mainly to the smaller wastewater facilities with no treatment (direct discharges). The change in reporting system from SSB-avløp to SESAM (1997/98) and later from SESAM to KOSTRA (2001/02) may also limit the comparability before and after those years.
A general problem still existing is that some wastewater plants, without notice, may report in under a different id-number than the one they've been assigned. However, this is believed to improve, now that the electronic forms contain more pre-filled information and become more user-friendly.
Use of sewage sludge has been reported in different ways after KOSTRA took over. The 2004 reporting was carried out on aggregated municipality level, but this was changed back again to reporting on sludge treatment plant level in the 2005 data collection.
The category deposited was not included as a separate use-category in 2003 due to a ban on deposition of wet organic waste, including sewage sludge (Regulation on deposition of waste (Department of Environment 2004). Because it is not totally face out the category was re-introduced again in 2004 in order to cover these amounts in the official statistics. The changes in the reporting, in addition to that the reported data is of various quality, result in some uncertainty in the statistics.
The statistics is related to other statistics concerning discharge and pollution of water. The discharge figures of the wastewater sector, together with the similar figures from agriculture, industry and aquaculture, add up to a national account on nitrogen and phosphorous discharges for Norway. Norwegian Institute for Water Research (NIVA) publishes the account every year in their so-called TEOTIL-report.
The statistics is also related to statistics of municipal residential charges, turnover from sewage and refuse activities, sewage and refuse disposal (structural business statistics), Municipal wastewater treatment and KOSTRA - municipal water supply
Reports on wastewater are available from Statistic Norway's Internet homepage: http://www.ssb.no/english/subjects/01/04/20/
Today's statistics: http://www.ssb.no/english/subjects/01/04/20/var_kostra_en/
The raw data is saved in text-format. Revised data sets are saved in Oracle-databases here with Statistics Norway. The Pollution Control Authority also has a copy of the dataset.
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