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MAGISTRÁT HLAVNÍHO MĚSTA PRAHY
PRAGUE CITY HALL

Ročenka – zpráva o stavu životního prostředí
Yearbook – report on state of the environment

 
 
 

B2.3  WASTE WATER

B2.3.1  Legislation requirements for the waste water treatment in the Czech Republic

The Member States of the European Union are bound by the Council Directive 91/271/EEC of 21 May 1991 on treatment of urban waste water. In the Czech Republic the fundamental legal regulation of water management is the Act No. 254/2001 Code, on water and amending certain acts (hereinafter as the Water Act), which is harmonised with the EU legislation. In accord with the Water Act the Government of the Czech Republic established acceptable values of pollution for the wastewater discharged into water courses (emission standards) and acceptable pollution of watercourses (immission standards) in the Order of Government No. 61/2003 Code on indicators and values of acceptable pollution of surface water and wastewater, on details of the permit for the waste water discharge into surface water and into sewerage systems, and on sensitive areas. This Order of Government was amended by the Order of Government No. 229/2007 Code.

Requirements for pollution released in waste water discharged are, according to the aforementioned regulations, stricter in the Czech Republic than those imposed by the EU directive (Directive 91/271/EEC on urban waste water treatment).

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B2.3.2  Disposal and treatment of wastewater

Sewerage system

The downtown sewerage system in Prague was founded at the beginning of the last century as an integrated sewerage system taking the mixed sewage and rainwater in the same pipes. The newly built housing estates at the Prague outskirts have separated sewerage systems, which do not mix together sewage and rainwater and taking them away in separated systems. The housing estates sewerage systems are connected to main sewers of the Integrated Centralised Sewerage System. This system disposes waste water to the Central Waste Water Treatment Plant (hereinafter as the CWWTP) on the Caesar Island in Bubeneč through seven main sewers.

Besides this Central WWTP, there are other auxiliary (local) waste water treatment plants (hereinafter as the WWTPs) under operation on the City territory, which mostly serve for wastewater treatment of water from territories of respective City Districts, which are located in the City outskirts and are not connected to the Prague Central Sewerage System (in total 26 WWTPs and two more for the Ruzyně Airport). Waste water to these WWTPs is taken to them mostly by separated sewerage systems. All local WWTPs are compliant with water management limit values in accordance with the European directive.

At present roughly 99% of the whole Prague population of 1.25 million inhabitants is connected to the sewerage system. All wastewater treated in the CWWTP and in local WWTPs is discharged into water courses and is not reused.

Tab. B2.3.1 Technical data and operational data of waste water disposal and treatment in the City of Prague provided
by the company of PVK, a. s., 2009

Počet obyvatel napojených na kanalizaci pro veřejnou potřebu
Number of inhabitants connected to the public sewerage system

cca 1,23 mil. / million

Délka stokové sítě / Length of the sewerage system

3 745 km

Délka kanalizačních přípojek / Length of sewerage system branches

930 km

Počet kanalizačních přípojek / Number of sewerage system branches

89 971 ks

Počet havárií na kanalizaci a přípojkách
Number of failures of the sewerage system and branches

2 588 (z toho 1 993 ucpávek)

Počet čerpacích stanic / Number of pumping stations

281

Počet čistíren odpadních vod
Number of waste water treatment plants

Ústřední čistírna odpadních vod v Bubenči (ÚČOV)
Central Waste Water Treatment Plant in Bubeneč (CWWTP)
+ 21 pobočných čistíren / local waste water treatment plants

Množství vyčištěné odpadní vody, celkem
Amount of treated waste water, total

  – ÚČOV / CWWTP

  – pobočné ČOV / local WWTPs

123 194 204 m3

115 185 343 m3 (93,5 %)

8 008 861 m3 (6,5 %)

Source: PVK, a. s.

Fig. B2.3.1  Amounts of waste water treated in the CWWTP and in local WWTPs

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Source: PVK, a. s.

Fig. B2.3.2  Shares of waste water treated in the CWWTP and in local WWTPs in 2009

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Source: PVK, a. s.

City development in relation to the completion and reconstruction of the sewerage system network

For the sake of the high increase in new development on the outskirts City Districts the population is growing, the waste water production and therefore troubles with waste water treatment plants capacity are growing as well. Capacity of local WWTPs is being quickly used out, so they must be expanded and reconstructed. Recently, some of the local WWTPs has reached limits values and the planned development sets cannot be connected to the sewerage system till such modifications are completed (for instance, WWTPs in Uhříněves - Dubeč, Miškovice, Běchovice VÚ, Královice, Vinoř, Kbely, Horní Počernice - Čertousy, and Sobín).

The local WWTPs are almost all equipped with systems for nutrient removal (nitrogen and phosphorus) and are complaint with emission limits established by the water management authority. Nevertheless, at present the CWWTP is not able to comply with the requirements of the OG CR No. 61/2003 Code for the indicator of total nitrogen, however, it underwent a partial reconstruction, and therefore the Prague City Hall has been preparing a vast reconstruction and expansion of the CWWTP.

Evaluation of the CWWTP operation

Evaluation of the CWWTP operation is based on compliance with values permitted by the City Development Authority of the Prague City Hall Ref. No. 76063/2000/VYS/Tr of 22 November 2000 for waste water discharge from the Central Waste Water Treatment Plant Prague into the Vltava River water course at the stream kilometre 43.3.

Tab. B2.3.2 Average concentrations of pollution and the overall pollution balance and treatment effectiveness in the CWWTP in 2009

Ukazatel kvality
Quality indicator

Přítok
Inflow

Odtok
Effluent

Účinnost
Effectiveness

průměr
average value
[mg.l-1]

celkem
total
[t.rok-1] / [t.year-1]

průměr
average value
[mg.l-1]

celkem
total
[t.rok-1] / [t.year-1]

průměr
average value
[%]

BSK5 / BOD5

257,0

29 647

5,4

625

97,9

CHSK / COD

635,0

73 174

36,1

4 162

94,3

Nerozpuštěné látky
Insoluble matter

339,0

39 098

8,4

965

97,5

N-NH4

29,5

3 399

3,7

426

Nanorg / Nin

30,3

3 493

16,5

1 906

Nc

54,5

6 274

19,8

2 276

63,6

Pc

6,5

744

0,7

79

89,4

Source: PVK, a. s.

Fig. B2.3.3  Average flow rate of waste water in the CWWTP, 1996–2009

b2_3_03

Source: PVK, a. s.

Fig. B2.3.4   Permitted and discharged annual amounts of the discharged pollutants from the CWWTP Prague, 2000–2009

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Note: Results in 2007–2008 are affected by the deterioration of treatment process which happened following to accidental inflow of a great amount of mud, which was discharged into the sewerage system without permission in autumn 2007 when Kyjský Lake was cleaned off mud. Results of 2002 were affected by the deluge. Limit values for the acceptable pollution discharged were temporarily adjusted in 2002.

Source: PVK, a. s.

In 2009 the average daily inflow of waste water to the CWWTP, including rainwater inflow, was 315,756 m3.day-1, that is 3.65 m3.sec-1. This means that compared to the previous years, the permanent trend to a slight decrease, which is caused either by households and companies savings (using appliances with lower water consumption), and either by reconstructions and repairs of the public water mains and sewerage systems carried out, which limit the inflow of ballast water into the sewerage systems, was stopped in 2009.

The operation of sludge management at the CWWTP, where sludge produced at the waste water treatment is further processed, has been partially limited over a long time. Reconstruction of respective pairs of digesters is gradually performed. The CWWTP sludge management processed in 2009 in total 36,969 tonnes of dry matter of the sludge produced, which corresponds to volume produced of 1,890 m3.day-1 at the average dry matter content of 5.4% in the sludge. In 2008 there were 69,366 tonnes of dewatered sludge handed over for further processing.

Pollution produced, which arrives in waste water at the WWTP is limited by values established in sewerage system rules developed for respective catchment areas of the WWTP. The operator (PVK, a. s.) provides for checking of producers concerning their compliance with the rules. Trouble is the still lacking discipline of the producers, which discharge banned substances into the sewerage system even if there is a risk of high sanctions when established limit values are exceeded. This is reflected in quality of sludge produced which then can find only a limited usage for fertilisation of agricultural land (for high content of heavy metals as chromium, lead, cadmium, and mercury).

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B2.3.3  General Drainage Plan for Prague

The General Drainage Plan for Prague (hereinafter as the GDPP) is one of the basic whole-City documents in the field of drainage and treatment of water and drainage of surface rainwater. The Plan solves and determines major development directions of the City drainage system. Drainage is solved in variants, including technical, economic, and environmental impacts. This concept represent a tool for the management and decision making processes for the maintenance and development of the City drainage system. It enables to proceed in an operative and systematic manner in investments. One of the General Plan outcomes is the Investment Plan and design of flood control system for the sewer system. Once phase I of the General Drainage Plan was completed in 2001 the company of PVS, a. s. the development of detailed phase II dealing in detail with drainage of respective partial areas.

In 2009 partial projects were made for areas Kbely - Vinoř and Modřany - Komořany within the gradual implementation of detailed phase II of the GDPP. Projects for the administration and updating of the GDPP were also secured.

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© Magistrát hlavního města Prahy | Prague City Hall
Únor 2011 | February 2011