Municipal wastewater, 2000

The figures are mainly published on national and country level, but also in part on municipality level.

Key figures are published annually in connection with Municipal-State-Reporting (KOSTRA) on the 15 ^th of Mars (un-revised) and 15 ^th of June (revised). In addition, a report is being published each year, usually in the end of the year, summarising the wastewater treatment situation in Norway.

The statistics is reported to EUROSTAT/OECD as part of their Joint Questionnaire on inland waters (JQ-IW).

The datamaterial is saved as text files. Revised dataset are also saved temporarily in different Oracle databases with Statistics Norway.

The Norwegian Environment Agency (Miljødirektoratet) have a copy of the same data.

The purpose with the statistics is to give an overview of the status and development in the municipal wastewater sector. Among other things, it provides information about number of wastewater plants, treatment capacity, type of treatment, degree of people connected, sludge disposal, discharges, economical figures in wastewater sector (investments costs and income), together with illustrating, on a municipal level, the relationship between revenues from wastewater fees, annual costs, and wastewater tariff.

Data collection was carried out sporadically in the 1980s, however since 1990 there's been a data collection on an annual basis. First it was administered under the name SSB-avløp, a co-operation between county administrations and Statistics Norway; secondly there was SESAM (1998-2001); and now finally, there's the Municipality-State-Reporting (KOSTRA) (from 2002).

Important user groups of the wastewater statistics are the different national and regional public administrations/governments, mainly the Ministry of Environment, Norwegian Environment Agency, the different county administrations and municipalities. To various degrees, other potential user groups are science, media, business and industry and NGOs.

Not relevant

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. The umbrella to this work is the Comprehensive Study on Riverine Inputs and Direct Discharges (RID).

The program annually provide a quantitative eveluation of all discharges from waterways into the coast and sea area covered by the Oslo-Paris Commission (OSPAR).

KOSTRA data are collected by Statistics Norway on behalf of the Climate and Pollution Agency with legal basis in the Pollution Control Act (13th Mars, 1981, no. 6). Statistics Norway can make use the collected data for official statistical purposes with legal basis in the Statistics Act. (16 ^th June 1989, no. 54, §2-2).

The Climate and Pollution Agency collect their data solely with legal basis in the Pollution Control Act (13th Mars, 1981, no. 6).

Council Directive of 21 ^st May 1991 concerning urban wastewater treatment (91/271/EEC).

All municipalities (complete collection).

Physical data: Complete collection. All the municipalities are reporting yearly on behalf of more than 2 700 wastewater facilities (approved for 50 population equivalents (pe) or more) and around 300 000 individual wastewater facilities, the latter most commonly situated in scattered settlements.

Financial data: Complete collection. Annual reporting for all municipalities.

Notably, since 2001, all municipalities have reported their accounts electronically with KOSTRA, and this created, together with the new account scheme, a way of utilizing the accounts as a powerful information source to financial statistics within municipal wastewater sector.

However, by collecting data directly from the municipality’s accounts, information from various organisation structures will not be collected because they are not visible in the account for the municipality. Therefore data for cost absorption since 2006 is collected via KOSTRA questionnaire 23 (Kostnadsdekning i vann, avløps- og avfallssektoren). The data reported must be limited to the instruction for calculation of full cost.

Data is collected electronically once every year, and the information should be in hands of Statistics Norway by 15 ^th 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 15 ^th of Mars. There's a second deadline on the 15 ^th of April for municipalities to correct possible errors in the figures just published.

The most updated and detailed theoretical framwork and methodology applied in wastewater statistics is published in Norwegian language only, see the report Municipal wastewater: Expenditures, investment, discharges, treatment and disposal of sewage sludge. Wastewater fees. A brief summary of the methodology is however presented below, while the remaining details is only available in Norwegian.

Calculation of discharges of phosphorous and nitrogen

Due to the fact that only part of wastewater facilities undertake direct analysis of pollution loads and discharges, some level of estimation and the use of standard factors needs to be applied in the calculations. Thus, total discharge and treatment efficiency figures of nitrogen and phosphorus are in part based on estimations (see below for further details).

The following calculation procedure has been applied to municipal wastewater facilities, capacity of 50 population equivalents (pe) or more:

1. If information on discharge quantity, expressed as kilogram per year, has been reported, then this information will be used directly.
   
   
2. If no information as specified in point 1 above has been reported, but outflow concentrations and average water quantities have been provided, then discharge quantity is calculated in kilos per year from the following equation:
   
   Concentration (mg/l) x average water quantity (m ³ /year) / 1000
   
   
3. If neither point 1 nor 2 above can be calculeted, then discharge quantities will be estimated by multiplying the number of people connected to the wastewater facility with a standard factor for average discharge per person and another factor for standard treatment efficiencty. These factors are listed below:

Discharge of nitrogen and phosphorous per year at the outlet of wastewater facility can then be estimated from the following equations:

Phosphorous: ((number of persons connected x 1.8 x 365) / 1000) x average treatment efficiency

Nitrogen: ((number of persons connected x 12 x 365) / 1000) x average treatment efficiency

Small wastewater treatment facilities (less than 50 pe), usually individual plants, make use of the same set of standard factors on average discharge of nitrogen and phosphorous per person per day, as mentioned above. However catogories for type of treatments and treatment efficiencies differs somewhat. Therefore, treatment efficiencies for small wastewater treatment plants, in percentage, are specified below:

_{* Wastewater from sealed tanks are normally delivered to other wastewater plants and treated elsewhere, thus, discharge and treatment efficiency calculations are included with them.}

_{** Standard factor set up in collaboration with Bioforsk.
*** Standard factor set up in collaboration with Norsk Vann.}

Calculation of discharges of organic material, heavy metals and persistant organic pollutants

The calculations are mainly built on the method suggested by Blytt og Storhaug (2008) . The method was originally designed for heavy metals and persistant organic pollutants, but it has now also been extended to cover also organic material (biological oxygen demand (BOD ₅ ) and chemical oxygen demand (COD)). The statistics presented here covers only discharges from treated wastewater to the water recipient. In addition the statistics, so far, only covers discharges from wastewater treatment facilities 50 pe or larger.

The following parameters are included in the statistics:
- Arsenic (As)
- Cadmium (Cd)
- Crom (Cr)
- Copper (Cu)
- Mercury (Hg)
- Nickel (Ni)
- Lead (Pb)
- Zink (Zn)
- DEHP
- Biological oxygen demand (BOD ₅ )
- Chemical oxygen demand (COD)

A. Annual discharge from wastewater facilities reporting annual discharge data
Calculation of discharges from these wastewater facilities are relatively straight forward. The discharges constitute the total sum of calculated discharges from all these facilities (either reported as (1) kg discharge per year or (2) the combination of the volume of water treated and average concentration of the parameter).

According to the Forurensningsforskriften ("Pollution regulation", FOR 2004-06-01 no 931), chapter 11, wastewater treatment plants larger than 20 000 pe are required to carry out analyses for content of heavy metals, while wastewater treatment plants larger than 50 000 pe in addition also are required to analyse for a selection of organic pollutants. That means large wastewater treatment plants directly or indirectly report actual discharge data which can be used for statistical purposes, while discharges from smaller treatment plants are largely unknown.

B. Annual discharge from wastewater treatment plants with no reported discharge data
Calculation of discharges which are not covered by the Pollution regulation, or for some other reason are missing, will be estimated for. The estimations are based on standard factors - discharge per person connected. The data source to establish these factors are based on actualy data from treatment plants in "point A" above. Data on people connected to wastewater facilities exist in most cases, even if they don't carry out analyses, and thus, this informatio is the used to upscale discharges to national level.

Thus, for every wastewater facility in "point A" above with reported discharge data, we will first calculate a specific discharge for each chemical component (unit: microgram / person connected):

Spesific discharge = microgram discharge per year / number of people connected

This is carried out on every wastewater facility containing actualy data for every component being analysed. Then these wastewater facilities are divided into two categories based on their type of treatment:

• Treatment category I: direct discharges, mechanical and other treatment
• Treatment category II: chemical, biological, chemical-biological and natural purification

For each of these treatment categories, the median value for each heavy metal and each organic pollutant will become the overall specific discharge factor. "People connected" in the sense applied here means permanent residents who are being served by the wastewater facility through their pipeline system.

For example cadmium, there will be two spesific discharge factors, one for treatment category I and another for treatment category II. The same applies to all the other components in the statistics. The factors are updated each year based on the most recent data reported.

Please note! For BOD ₅ and COD, a 5 per cent trimmed average instead of median value has been used when establishing the spesific discharge factors. This deviates from the original method suggested by Blytt and Storhaug (2008). The reason for this adjustment in method is that this better explains the variation in discharges for these particular components. Spesific discharge factors for the different chemical components:

_{Source: `KOSTRA 2017-data (reported Spring 2018).}

When the spesific factores have been established, they are then applied to the wastewater facilities with no discharge data (in point B). For example if a treatment facility belonging to treatment category I has 1 500 people connected, the estimated discharge is then 1 500 people multiplied with the discharge factor for treatment category I.

In this way, by partly using data based on actual analyses and partly by using estimations/factors, the statistics on heavy metals and organic pollutants, one can then calculate a national discharge for the whole wastewater sector.


Additional calculation and adjustments for BOD ₅ and COD
For BOD ₅ and COD there exist an additional calculation compared to what is the case with heavy metals and persistand organic pollutants. It only applies in those cases when it has been reported (1) data on BOD ₅ , but not COD, or (2) data on COD, but not BOD ₅ . Both BOD ₅ and COD measure organic material, and in order to avoid too much estimations, discharges in these instances are calculated from a theoretical BOD ₅ /COD-relationship (source: KOSTRA 2012-data):

• Treatment category I: 0.50
• Treatment category II: 0.30

For example the BOD ₅ /COD-relationship in treatment category I of 0.50 means that the amount of BOD ₅ in average is 50 per cent of what is the case with COD. The BOD ₅ /COD-relationships above have been established based on wastewater facilities that reports both BOD ₅ and COD, and thus makes it possible to establish a more general BOD ₅ /COD-relationship. The relationship is then applied to those wastewater facilities that misses either BOD ₅ or COD in their reporting (but not both!). For example if a wastewater facility belonging to treatment category II is reporting 200 tonnes of BOD ₅ , but data on COD is missing in their reporting, then this facility will have a COD discharge of 200 tonnes / 0.30 = 667 tonnes. Opposite, if a wastewater facility belonging to the same treatment category reports 200 tonnes of COD, then the BOD ₅ discharge will be estimated to 200 tonnes * 0.30 = 60 tonnes.

Consequently, discharge from these "one-sided" reportings (wastewater facilities) will be calculated based on part factor (BOD ₅ /COD-relationship) and part discharge data and actual analyses (either BOD ₅ or COD). This is considered a "second best solution" for estimating discharges for these facilities as apposed to a complete factor calculation. 

Calculation of use of sewage sludge
The 2005-data-reporting introduced a new way of reporting sewage sludge compared to earlier years. Gross sewage sludge and its associated percentage dry weight are now included in the reporting compared to earlier it was only asked for dry weight of sewage sludge. In order to calculate the dry weight now, the information of percentage dry weight is essential. In cases where percentage dry weight is missing, then the following method has been applied to the data:

1. If percentage dry weight of the produced sludge product has been reported, but not for the amounts of sludge used, then this percentage has been applied.

2. If percentage dry weight of neither the produced sludge product nor the amounts used has been reported, a standard factor of 25 per cent dry weight has been applied.

Calculation of heavy metal content in sewage sludge

The calculation of average heavy metals in sewage sludge constitutes a weighted average of the reported figure; that is the content of heavy metals is weighted based on the amount of sludge reported for the different wastewater treatment plants. Thus, figures reported from larger treatment plants generally influence the final average figures more compared to smaller ones.

In the same way, maximum heavy metal content in sludge constitutes a weighted average figure of the values reported as maximum (as above, weighted against the amounts of sewage sludge disposed).

Calculation of number of small wastewater treatment plants (less than 50 pe) and their corresponding inhabitants connected.
Due to the fact that there is less reliable information available on smaller treatment plants, some estimation is necessary. Two estimation techniques may occasionally be applied:

1. Certain municipalities lack information on the distribution of inhabitants on type of treatment for smaller wastewater treatment plants. If the municipality has provided information on total amount of inhabitants connected, in addition to number of small treatment plants, the inhabitant distribution on type of treatment is estimated. The inhabitants are then distributed proportionally based on the number of treatment plants. For example lets say the municipality reports totally 3000 inhabitants connected to small treatment plants, 400 sludge separators, and 500 sludge separators with infiltration, but no distribution of inhabitants on types of treatment. Then the inhabitants connected is estimated to be 3 000x(400/(400+500)) = 1 333 inhabitants to sludge separator and 3 000x(500/(400+500)) = 1 667 inhabitants to sludge separators with infiltration, totally 3 000 inhabitants.

2. If the municipality lacks information on number of small treatment plants, but has information on the number of inhabitants connected, then this information may be used for estimation purposes. A theoretical connection factor based on the reported material is being applied. In 2012, this factor was 2.4 inhabitants per wastewater treatment plant (median value). For example if a municipality has the following information: 1 000 inhabitants connected to sludge separator, the estimated figure turns out to be 1 000/2,4 = 417 small treatment plants.

Economic data
Due to missing or incomplete data, estimates are made for some municipalities. This is done because figures for the entire country are to be estimated. For municipalities which do not report figures for operating expenditures and capital costs figures have been estimated. The estimates are based on the data from the municipalities that have reported data. The basis for the estimation is that there are a correlation between the variable and an explanatory variable (population in the municipality). The estimates for the individual municipality are not published.

Not relevant

Not relevant

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.

In connection with introduction of new regulation on wastewater treatment the 2007/12 report made some changes to the definition of capacity. Earlier the concept of hydraulic capacity (PE) was used, but now capacity is defined according to Standards Norway and the new wastewater regulation as population equivalents (pe). The counties have been involved in the updating process of capacity, partly assisted by the municipalities. The capacity from 2004 and earlier is however still hydraulic capacity in the official statistics.

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 on individual wastewater treatment plants covered until the year 2000 received wastewater which in amount and quality corresponded with 7 houses or vacation homes. After that the definition shifted and only plants less than 50 pe were covered in the definition of individual wastewater treatment plants. Hence, the statistics may therefore not be readily comparable before and after that time.

In recent years, a few re-calculations has been carried out in the earlier published statistics. The reason is commonly due to correcting erroneous data in the times series. Note then that the last and current version of the statistics will always be found in Statbank.

From the reporting year 2006, the KOSTRA-questionnaire for cost coverage is changed. This is done to obtain figures for the municipalities' income from fees, and the fee calculation basis for the areas that are subjected to the principles for full cost. The reason for the changes is that the previous key figure calculations partly were based on data with origin in the reported annual accounts, and partly based on data reported in the form for cost coverage. Due to the different ways to organise the municipal services (e. g. intermunicipal cooperation, municipal undertaking), it is not possible to find all the data needed in the annual accounts form the municipalities.