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Waste waters

Last update of indicator 22.11.2021

Indicator definition

The indicator describes the amount of waste waters discharged into surface waters, including pollution indicators, as well as the share of population connected to public sewerage.


%, thous. m3, tons, number


Related policy documents and targets

Strategy of the environmental policy of the Slovak Republic - Greener Slovakia (2019)
Sustainable Use and Effective Protection of Natural Resources
Goals: Agglomerations with more than 2,000 inhabitants equivalent will reach 100% and agglomerations with less than this number will reach 50% share of drainage and water treatment by 2030.

1. Enough clean water for everyone

 1.2.Increase in the Proportion of Treated Waste Water

- Where it is efficient, the public sewer system will be completed also in agglomerations with less than 2,000 inhabitants, even in locations that have had limited opportunities to apply for a financial contribution.
- If it possible in regards to the local and regional conditions, Slovakia will make use of the innovative (environmentally friendly) infrastructure (e.g.vegetation, membrane, container waste water treatment plants, etc.) and decentralized cleaning.
- Rainwater in Slovakia is mostly discharged through a unified sewer network into the waste water treatment plant, and thus part of the waste water. The optimization of the waste water infrastructure will enable rainwater and wastewater to be collected separately.

Orientation, principles and priorities of Slovak Republic water management policy by 2027 (2016)

3. Principls a priorities of the Slovak republik water management policy by 2027 and framework procedures in achieving the objectives
Priorities of water management 

With a view to water status improvement:
  • Implement the necessary measures aimed at the significant reduction of pollutants in discharged waste water or special waters. When discharging waste water, priority substances contained therein must be gradually decreased and priority hazardous substances should be progressively reduced in order to achieve a desired objective, i.e. the good water status;
  • Subsequently, after the fulfilment of the Slovak Republic´s commitments to the European Union, in relation to the collection and treatment of waste water in the agglomerations above 2,000 p.e., to focus attention on the gradual elimination by organic pollution and nutrients from point sources of pollution also in the agglomerations below 2,000 p.e., where the water body is in a bad status and measures focused on the collection and treatment of waste water will demonstrably contribute to the significant improvement of water quality;
  • Consistently address the reduction of pollution from agriculture in vulnerable areas in accordance with the requirements and procedures arising from the Council Directive 91/676/EEC, concerning the protection of waters against pollution caused by nitrates from agricultural sources, and wherever the good water status hasn´t been achieved and intense agricultural activity has been performed. Measures must be designed and implemented so as to prevent penetration of nitrates from agriculture into waters. When reducing the pollution from agricultural production, it is necessary to consistently apply all the principles of the EU Common Agricultural Policy and Good Agricultural Practice;

Plan of public sewerage systems development (2021)

7. Targets of public sewerage systems development
Public sewerage system development until 2027 is formulated as follows:
I. Priority implementation of sewerage system structures
  • construction, extension and increasing the capacity of sewer networks in agglomerations bigger than 10,000 EC (equivalent citizens); construction, extension and increasing the capacity of waste water treatment plants bigger than 10,000 EC,
  • construction, extension, reconstruction and increasing the capacity of sewer networks in agglomerations from 2,000 up to 10,000 EC; construction, extension and increasing the capacity of waste water treatment plants from 2,000 up to 10,000 EC,
  • in agglomerations up to 2,000 EC, construction of waste water treatment plants if sewer networks have already been constructed at least at 80% of the whole agglomeration in question,
  • construction of sewer networks and waste water treatment plants in agglomerations up to 2,000 EC that are located in protected water management areas with large-capacity resources of underground water and that are aimed at preventing threatening of the quality and quantity of underground water in order not to threaten their utilization.

 II. Continuous implementation of sewer structures

  • continuous construction, extension and increasing the capacity of sewer networks and waste water treatment plants in all municipalities of the SR (except for municipalities falling under the National Programme for Implementing the Directive of the Council No. 91/271/EEC).


The Slovak Republic Strategy for Adaptation to Adverse Effects of Climate Change- Update (2018)

1.Strategy Goals

The main goal of the updated the Slovak Republic Strategy for Adaptation to Adverse Effects of Climate Change is to prepare Slovakia for tackling the adverse effects of climate change, deliver comprehensive information about the current state of adaptation processes in Slovakia, and based on their analysis establish an institutional framework for a coordinating mechanism which will ensure effective implementation of adaptation measures across all levels and in all areas, as well as improve general awareness of the domain.
5. Impact of climate change on select areas and recommended adaptation measures
5.4. Water regime and water management
Adaptation measures in local conditions should aim at compensating for the instances of drought, that is, the decrease of flows of water and water yields, as well as minimising the negative consequences of floods, especially flash floods in montane and submontane regions. Climate change adaptation within the domain of water management should be oriented towards implementing measures which will create the conditions for better water outflow management in catchment areas. In the domain of water management elements of green and blue infrastructure, green structural approaches and non-structural adaptation concepts should be prioritised over elements of grey infrastructure whenever it is technically possible and efficient to do so. Adaptation measures should focus on preserving or improving the current state of water, with the aim of achieving its good state, efficient and sustainable utilisation of water resources, protection against floods and contribution towards protection of nature and land and support with ecosystem services provision. It is important to create space for a wider application of so-called "green" measures in catchment areas where the main goal is to increase the land's adaptability through regeneration and improvement of efficiency of ecosystem functions of the land. "Green" measures are recognised as the better environmental choice, that is, as supplementary-mitigating measures with the aim of minimising the consequences of grey infrastructure, assuming that they are equally effective or more effective in regards to set goals.
Water is becoming a critical strategic stock of the state and it is necessary to protect it and manage its rational and efficient use in line with the goal of ensuring sustainable development. Justifiably, the highest priority is given to water sources, their protection and the need of their more efficient use.

Proposed adaptation measures
-slowing down of water outflow from catchment areas
-decreasing of the maximum flow of floods
-risk assessment
-water management

The Protocol on Water and Health - to the Convention on the Protection and Use of Transboundary Watercourses and International Lakes, 1992 - National objectives of SR III (2014)

The reason for the Protocol´s objectives update in 2014 is their fulfilment, or the need of extending the deadlines for the fulfilment of objectives which are still actual, as well as determining new national objectives conditioned by the situation change and the occurrence of new problems to which the attention must be paid, and which seem to be important in terms of Protocol´s objectives implementation in SR. SR has defined the national objectives already for the third time since the Protocol entered into force.

National objectives of SR III

National objective no. 5: Improving the situation of sewerage, treatment and discharge of municipal waste water
Date of fulfilment: y. 2020, or 2023

Key question

Has the pollution of surface water caused by waste water discharges been reduced?

Key messages

  • In 2020, the production of waste water decreased by 27.8%, in comparison to 2005 by 32.3%. However, compared to 2019, the wastewater production increased by 4.6%.
  • In 2020,the amount of organic pollution characterized by CODCr and Ntot were decreased, BOD, Ptot and NESuv parameters, were at same level as in previous year.
  • In 2005, 56.7% of the population was connected to public sewerage, and 69.69% of the population was connected in 2020.
Change since 2005 Change since 2015 Last year-on-year change
emo_smile Pozitivny trend emo_neutral
The quantity of waste water decreased, which resulted in a decrease in pollution indicators.
Since 2015 the amount of waste water had a fluctuating character. The pollution of waste water had a declining trend.
An increase was reported in the production of waste water and the pollution was at the same level.


Summary assessment

Detailed assessment

The amount of discharged pollution is declining which is related to continuous completion of municipal wastewater treatment plants (WWTP), and also to the reduction in production in some industrial areas. In terms of production of wastewater and pollution by substances, the size of agglomerations is formed, in addition to permanent and temporary resident population, also by the production of wastewater from processing industry, which is connected to a public sewage system.
In 2020, the total volume of wastewater (WV) discharged into surface waters amounted to 636,640 thousand m3 which, compared to the previous year, was an increase by 27,968 thousand m3 (4.6%); in comparison to 2005 it is a decrease by 245,306 thousand m3 (28.0%).
The share of discharged treated waste waters to total volumes of waste waters discharged into watercourses in 2020 amounted to 93.50%, while in 2005 this figure was only 71.2%.

The main sources of organic pollution of water bodies are residential agglomerations, industry and agriculture.

During the whole evaluation period of 2005 - 2020 there was reported a decrease in the amount of discharged pollutants contained in wastewater; this decrease was more than 80% for IS, BOD5, CODCr  and NESuv.  A relative disproportion between a slight fall in the WV volume and a significant decrease in the amount of pollutants in WV was associated with the introduction of modern production technologies, as well as with the implementation of more efficient wastewater treatment processes.

Compared to the previous year, there was a decrease in wastewater pollution indicators - dichromate chemical oxygen demand (CODCr) by 176 t. yr-1, insoluble substances (IS) by 136 t. yr-1 and total nitrogen (Ntotal) by 79 t. yr-1. Biochemical oxygen demand (BOD5), total phosphorus (Ptotal) and non-polar extractables (NESuv) were approximately at 2019 levels.

Major producers of waste waters are municipal wastewater treatment plants.
In 2020, a total of 460 mil.m3 of wastewater was discharged into public sewer (administered by municipalities and water companies), which represented an decrease by 33 mil.m3 in comparison to the previous year, and the amount of treated wastewater discharged into the public sewer system reached the value of 456 mil. m3. In 2005, 443 mil.m3 of wastewater was discharged into the public sewerage system, with the amount of 428 mil.m3 of treated waste water thereof.

Waters discharged by the public sewerage system (administered by water comapnies and municipalities) in 2020
Waters discharged by the public sewerage system Sewage Industrial and others Precipitation Separate Total
  (thousand m3 year -1)
Treated 132 141 85 099 51 455 187 017 455 712
Untreated 748 421 1 469 1 508 4 146
Total 132 889 85 520 52 924 188 525 459 858
Source: WRI
The development of public sewerage systems is far behind the development of public water supply systems. The number of inhabitants living in houses connected to public sewerage system in 2020 amounted to 3,805 thousand of inhabitants, which represents 69.69% of the total population. Out of 2,890 independent municipalities, 1,152 municipalities had the public sewer system built (i.e. 39.86% of the total number of municipalities in SR). In 1990, 50.8% of the population was connected to the public sewerage, and in 2005 it was 56.7%. In the period 2000 – 2020, the number of population connected to public sewerage increased by 849,000.

Public sewerage systems in municipalities (administered by water companies and municipalities) in 2020

Number of independent municipalities Number of municipalities with public sewerage systems % of municipalities with public sewerage systems
Bratislavský 73 50 68.49
Trnavský 251 158 62.95
Trenčiansky 276 101 36.59
Nitriansky 354 137 38.70
Žilinský 315 179 56.83
Banskobystrický 516 146 28.29
Prešovský 665 226 33.98
Košický 440 155 35.23
Total 2 890 1 152 39.10
Source: WRI, SO SR
In 2020, 727 wastewater treatment plants were administered by water companies, municipalities and other entities, while in 2005 there were 442. The largest share is represented by mechanical-biological WWTP. In 2020, the total capacity of wastewater treatment plants (WWTP) was 1,713.4 thousand m3. day-1.


Ing. Ľubica Koreňová, SAŽP,

Related definitions:

Connection rate of public to public sewerage is a percentage of the population connected to the sewage network.

Waste water is water used in residential, manufacturing, agricultural, medical and other buildings and facilities or means of transport, if it has altered quality after its use (composition or temperature). The waste water may be sewage, industrial and municipal (Section 2 point. j) of the Act no. 364/2004 Coll.)

BOD5 is biochemical oxygen demand in 5 days, and it is the amount of oxygen consumed by microorganisms during biochemical oxidation of organic matter in aerobic processes, and without the concurrence of photosynthesising microorganisms over a certain time.

CODCr is a chemical demand by dichromate and determines the amount of oxygen required for the oxidation of organic substances, using oxidizing agents.

IS - insoluble substances


In the water management balance of surface water amounts there are recorded all users abstracting surface water in the amount of over 15, 000 m3 annually, or over 1, 250 m3 monthly. In discharges records, there are included all users that discharge more than 10, 000 m3 per year or more than 1, 000 m3 to surface waters.
Balance calculation – is done in the balance profiles network for all 12 months of the calendar year and an annual average in flow units (m3.s-1). For each balance profile the following balance characteristics are determined and given:
  • The total surface water abstractions (PO)
  • The total groundwater abstractions (PZO)
  • The total discharges into streams (V)
  • Change of flow rate (X)
  • Minimum balance flow rate (MQ)
  • The minimum required flow rate (MPP)
  • Influenced flow rate (E)
  • Impact of reservoirs (N)
  • The impact of water transfers and manipulation in partition objects (P)
  • Flow rate affected by reservoirs, water transfers and partition objects (ENP)
  • Net flow rate (C)
  • Long-term flow rate (D)
  • Coefficient of water content (KV)
  • Balance status (BSC, BSENP)
  • Resource capacity (KZC, KZENP)

More detailed information and description of the methodology:
Water management balance of SR

Data sources:


Related indicators:


Related international indicators:


Linked references: