PUBLIC SEWAGE SYSTEM, 2020

In 2020, the total volume of waste waters amounted to 356 149 thousand m³, which means it decreased by 1.4% compared to 2019.

Out of the total volume of waste waters, 189 535  thousand m³ were from households and economic activities (decrease of 2.3%), while 166 614  thousand m³ were other waste waters (precipitations, etc.).

The volume of waste waters discharged from households decreased by 1.2%, while in economic activities, it decreased by 4.5% compared to the previous year.

In 2020, there were 298 182 thousand m³ of treated waste waters, which was 1.1% less than the total volume of waste waters in 2019.

Untreated waste waters amounted to 57 967 thousand m³, which was 3.3% less than in the previous year.

The public sewage network in 2020 was 13 453 km long, which was 2.2% more than in 2019.

The total number of waste water treatment plants was 174 in 2020. The number of primary treatment plants increased by 10.2% and of secondary treatment plants by 1.1%.

More detailed data will be available in the database on 23 July 2021.

 

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NOTES ON METHODOLOGY

Sources and methods of data collection

The data on the public sewage system are collected by using the annual statistical survey entitled the Annual Survey on Public Sewage System (VOD-2K form) on the basis of the Official Statistics Act (NN, No. 25/20).

Reporting units are public suppliers of public sewage system services. According to the Water Act (NN, No. 66/19), the public supplier of sewage system services is a company in which all shares or equity shares are held by local self-government units or companies in which all shares or equity shares are held directly by local self-government units, that is, an institution founded by a local self-government unit.

The report is filled in by legal entities and parts thereof that are registered, according to the NKD 2007. (NN, Nos 58/07 and 72/07), in section E Water supply; sewerage, waste management and remediation activities, class 37.00 Sewerage.

Coverage and comparability

The source for the address list is the Statistical Business Register.

The survey provides basic data on waste waters, their treatment and discharge as well as on the public sewerage network and waste water treatment plants.

Definitions

Public sewerage means the activity of collection of waste waters, their transport to a waste water treatment plant, treatment and direct or indirect discharge into surface waters, treatment of sludge generated in the process of waste water treatment, if the above is conducted through public sewerage facilities, and management of these facilities; public sewerage also includes pumping and transport of waste water from sump pits.

Waste waters are all potentially polluted industrial, sanitary, rainwater and other waters.

Treated waste waters comprise all amounts of waste waters treated by using either primary (mechanical), secondary (biological) or tertiary (combined) treatment method.

The primary treatment includes the application of physical and/or chemical processes by which at least 50% of suspended solids are removed from the waste water, while the BOD₅ value decreases by as much as 20%, as compared to its value in the influent waters.

The secondary treatment includes the application of biological and/or other treatment processes by which the concentration of suspended solids and BOD₅ decreases by 70% to 90% and the concentration of COD by at least 75%.

The tertiary treatment includes the application of physical and chemical, biological and other treatment processes by which the concentration of nutritious matters in influent waste waters decreases by as much as 80%, which means that other pollutants, which could not be removed to that extent in the secondary treatment, are now removed as well.

Discharged waste waters consist of discharges of treated and untreated waters. The waters can be discharged into ground waters, waterflows, reservoirs, lakes and the sea.

Public sewage network is a network of enclosed public drains and sewers used either for draining of both waste and atmospheric waters together (general water sewage system), or for separate draining of waste and atmospheric waters (separation water sewage system).

Total length of the public sewage network is the length of the sewerage network of enclosed public drains and pipes for wastewater and atmospheric waters from settlements, without connections and networks within buildings.

Waste water treatment plants are devices for the treatment of waste water. They are divided to devices for the primary, secondary and tertiary treatment.

Abbreviations

BOD5	biochemical oxygen demand
COD	chemical oxygen demand
km	kilometre
m3	cubic metre
NKD 2007.	National Classification of Activities, 2007 version
NN	Narodne novine, official gazette of the Republic of Croatia
'000	thousand

 

 

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