9. Waste water management

9A. Present Situation

Please complete the following table providing the most recent data that is available:

Indicator Unit Year of data

Percentage (%) of total annual generated waste water load, connected to waste water collecting system + urban waste water treatment plants (UWWTPs)

100 % 2015

No of wwtp 1

Total Design Capacity (p.e) 170,333,090 p.e 2014

Total Load Received by WWTP (p.e) 14,485,000 p.e 2014

Total annual generated waste water load of the city (in p.e.)

289,700 p.e 2014

Treatment level which is applied in each uwwtp: secondary or more stringent; in this case, type of treatment: nitrogen and/or phosphorus removal, disinfection etc.

Stage 3 treatment

(chemical and

biological)

2014

Describe the present situation in relation to waste water management, including any relevant disadvantages or constraints resulting from historical, geographical and/or socio-economic factors which may have influenced this indicator area. Where available, information/data should be provided from previous years (5 – 10) to show trends. Describe the current general features of waste water treatment according to national requirements and the requirements of the Urban Waste Water Treatment Directive (UWWTD, 91/271/EEC). Include data and a short explanation for the following specific indicators. Provide explanation in the case of missing information.

1. Provide an indication of the fraction (%) of the total annual generated waste water load of the city coming from population and from idustry (also specifying type of industry, when information is available); The most advanced treatment level at UWWTPs (primary treatment, secondary treatment, tertiary treatment;

2. Proportion (%) of total annual generated waste water load, not connected to waste water collecting systems, and explanation of the type of waste water treatment applied to this fraction (reference to individual or other appropriate systems, i.e., IAS);

3. If the city is located in an EU Member State include data on waste water treatment obligations according to the UWWTD (based on city's size and nature of the area of discharge);

4. Waste water collecting systems: main type of collecting system (combined/separated) and annual proportion (%) of COD-loads discharged via storm water overflows;

5. UWWTPs: Organic design capacity (p.e.), most advanced treatment level, annual incoming and discharged loads (t/a) of BOD5, COD, Ntot and Ptot and treated waste water amounts (m³/a) of all UWWTPs serving the city. If the city is located in an EU Member State, indicate whether the UWWTP complies with the treatment requirements under the UWWTD;

6. Annual amounts of generated sewage sludge (t/a) and description of treatment/disposal pathways (% of total amount).

7. Provide data on annual energy consumption for wastewater treatment in Kwh/year/p.e., if available. Further information (e.g. on energy efficiency at UWWTPs, treated waste water re-use, economic sustainability, use of integrated constructed wetlands or other GI/nature-based solutions) is highly appreciated. (max. 600 words & 5 graphics, images or tables)

The sewerage system of Tallinn consists of 21 separate (wastewater only) and seven combined (wastewater

and stormwater) catchment areas (Figure 1). Proportionally, the combined sewerage system covers ca 35% of

the territory of Tallinn, which means that ca 35% of stormwater passes through the wastewater treatment

station. The combined sewerage system is mainly located in the older districts of Tallinn, such as City Centre

and Northern Tallinn (Figure 2, Section 9B).

Figure 1. System of stormwater catchment areas and stormwater outlets in Tallinn

The wastewater is directed to the Tallinn (Paljassaare) wastewater treatment plant that is located on the

Paljassaare peninsula in Northern Tallinn (Figure 2). The water is directed from the wastewater treatment plant

to a distance of 2.8 km from the coast and a depth of 26 metres in the Tallinn Bay. Tallinn also accepts and

treats the wastewater of neighbouring local authorities (4% of volume).

Figure 2. Tallinn wastewater treatment plant (middle) is surrounded on two sides by the Paljassaare special

conservation area (left and front) that belongs to the network of NATURA 2000 sites

100% of the wastewater generated in Tallinn is treated. 99.8% of the population of Tallinn have joined the

public sewerage system, but in the case of the remaining 0.2%, this is not economically practical. They are

obliged to collect wastewater in liquid-proof tanks from which it is discharged into the sewerage system. The

quantity of wastewater passing through the treatment equipment is 41-57 million m3 per year, depending on the

quantity of stormwater that has flowed into the combined sewerage system.

The pollution load of Tallinn has decreased in the last decade (Table 1). In 2014 it was 289,700 population

equivalents, ca 73,000 (25%) of which comprised industry.

Table 1. Pollution load in the last 10 years (in population equivalents)

Year 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

351,683 313,334 311,017 329,367 295,467 308,833 272,383 282,567 311,542 289,700

Mechanical and chemical-biological treatment technologies are used at Paljassaare wastewater treatment

plant. The mechanical treatment part consists of mechanical grids, sand traps and primary settlement tanks.

The biological treatment of wastewater uses aerotanks, secondary settlement tanks and a biofilter (purification

level III). A methanol station, air blowers and coagulation assembly support the technological processes.

Approximately 0.3% of the wastewater entering the treatment plant has passed through a preliminary purifier

(mainly an oil, sand or grease trap).

The designed parameters of the treatment plant are as follows: wastewater reception volume 127.75 million

m3/y; BOD7 – 10,220 t/y; suspended solids – 17,885 t/y; Ntot– 2190 t/a; Ptot – 328.5 t/y.

The wastewater treatment plant has achieved high purification efficiency: 98% for BOD7, 97% for suspended

solids, 84-86% for total phosphorus, and efficiency of nitrogen separation with a biofilter of 80-90% (Table 2).

Table 2. Purification efficiency of Tallinn wastewater treatment plant from 2005-2013

Year Suspended solids BHT7 Ngen Pgen

in

mg/l

out

mg/l

standard

mg/l

in

mg/l

out

mg/l

standard

mg/l

in

mg/l

out

mg/l

standard

mg/l

in

mg/l

out

mg/l

Standard

mg/l

2005 202 5.0 15 41.0 13.2 10 6.76 0.96 1

2006 232 4.9 15 47.6 10.9 10 7.65 0.98 1

2007 343 9.6 15 206 3.9 15 42.8 9.1 10 6.66 0.94 1

2008 334 9.1 15 197 3.7 15 42.1 9.9 10 6.12 0.96 1

2009 349 9.2 15 223 3.7 15 47.0 10.0 10 6.88 0.97 1

2010 366 10.5 15 207 4.1 15 48.5 11.9 10 6.82 0.97 1

2011 350 9.3 15 195 3.3 15 44.7 11.1 10 6.24 0.92 1

2012 312 7.4 15 161 3.0 15 42.7 6.3 10 5.57 0.76 1

2013 363 6.0 15 193 3.3 15 48.8 7.5 10 6.70 0.45 0.5

The treatment of wastewater in Tallinn complies with the requirements of the Urban Waste Water Directive

(92/271/EEC):

- all wastewater in Tallinn is treated chemically and biologically (stage three treatment);

- the indicator of the total phosphorus exiting the Tallinn wastewater treatment plant complies with

requirements (<1 mg/l in residential settlements of more than 100,000 people);

- since the launch of a denitrification biofilter in 2011, the indicator of the total nitrogen exiting the

treatment plant has also complied with requirements (<10 mg/l in residential settlements of more than

100,000 people).

In addition to the Urban Waste Water Directive (92/271/EEC), the indicators of the wastewater exiting the

treatment plant also comply with the recommendations of the international HELCOM committee.

The share of stormwater in the overall pollution load was studied in 2012. COD in stormwater has not been

studied, but the indicators of the remaining components are as follows: BOD – 0.049%; suspended solids –

24.9%; Ntot – 0.026%; Ptot – 0.046%.

27-30 tons of sludge is generated at the treatment plant each year. Since 2003 the sludge has no longer been

deposited in landfill, but is mixed with peat and composted instead. The resulting compost is used as a fertiliser

in landscaping and as a ground filler. 23-27 thousand tons of compost is made each year.

Figure 3. Sludge composting facilities at Paljassaare wastewater treatment plant

The biogas generated in the methane tank is used to heat the plant’s own buildings. 100% of the biogas is used

in winter and 20-30% in summer; the surplus is burnt in a residual gas burner.

Irrespective of investments made in Tallinn’s wastewater treatment system, it has been impossible to achieve

the good status of the coastal waters of Tallinn by 2015. These waters form part of the Baltic Sea ecosystem,

where water exchange occurs every 25-30 years on average. Since water exchange between the open sea and

coastal waters is good, the status of the coastal waters does not depend on pollution coming from land alone,

but also on the status of the open sea. HELCOM has developed recommendations for achieving the good status

of the Baltic Sea and found that achieving it throughout the sea – including coastal waters – will probably occur

by 2021 considering the implementation of the measures known today.

Figure 4. One of the most popular beaches in the city, which has been awarded the Blue Flag eco-label, is

located at Pirita on Tallinn Bay

9B. Past Performance Describe the measures implemented over the past five to ten years to improve waste water treatment. Comment on which measures have been most effective. If the city is located in an EU - Member State special reference should be given to non-expired deadlines for compliance with the UWWTD, when applicable (reference to Accession Treaties or sensitive areas under transitional period). Particular reference should be given to capacity building, measures for maintenance, management and restoration of waste water collecting systems and UWWTPs. (max. 1200 words & 5 graphics, images or tables)

The total length of the sewerage pipes in Tallinn is 830 km. 120 km of these are new pipes built during the last

10 years. Tallinn finished the canalisation of regions that were not covered by the public sewerage system by

the end of 2010, as a result of which 99.8% of the population are now connected to the public sewerage system.

In the last five years, the focus of Tallinn has been on the reconstruction of the sewerage network, because

the majority of sewerage pipes have exceeded their lifetime. There are more than 57 km of pipelines older than

70 years; 2 km are 60-70 years old; and 42 km of the pipes are 50-60 years old. The existing sewerage

pipelines are mostly made from concrete and plastic. Most collectors are older than 70 years and are mostly

made from concrete and asbestos cement. 13.33 km of new wastewater drainage pipes were built between

2011 and 2013. The new material used is plastic whose lifetime is 100 years compared to the 30 years of

concrete and asbestos cement.

All high-priority wastewater pump stations in Tallinn have been reconstructed in recent years. There are

more than 100 wastewater and stormwater pump stations in Tallinn, seven of them of high priority. The worn-out

equipment in them (pumps, non-return valves, valves, switchboards) has now been replaced. Frequency

converters were installed in several pump stations to prevent pressure gauges from breaking as a result of

possible hydraulic shock. Remote monitoring systems were installed in several pump stations, incl. all high-

priority pump stations.

The Tallinn wastewater treatment plant reconstruction project was completed in 2003 and has since been

gradually implemented. The wastewater treatment plant was constructed from 2003-2005 to guarantee the

required treatment effect, especially in respect of nitrogen. When 2002 and 2007 are compared, the treatment

efficiency of nitrogen increased from 57% to 75%, and to 85% in the case of phosphorus. The treatment

efficiency achieved in the case of BOD7 and suspended solids was over 95%. The designed capacity of the

plant in terms of nitrogen load was exceeded by 2010 and the phosphorus load indicator achieved.

A biofilter was launched at the wastewater treatment plant in 2011. It was built as part of the technological

process of the existing plant to guarantee sustainable and more efficient treatment of wastewater (Figure 1).

This is a secondary denitrification biofilter that reduces the concentration of nutrients (BOD, N tot, Ptot) in the

water that exits the plant. At present, treatment efficiency is 98% for BOD7, 97% for suspended solids, 84-86%

for total phosphorus and 80-90% for nitrogen separation with the help of the biofilter. The wastewater treatment

system is fully controllable and it has considerably reduced the pollution load on the Baltic Sea. In addition to the

Urban Waste Water Directive (92/271/EEC), the indicators of the wastewater exiting the treatment plant also

comply with the recommendations of the international HELCOM committee.

Figure 1. The biofilter at Paljassaare wastewater treatment plant guarantees even more efficient wastewater

treatment

Several studies have been carried out in the last 10 years to find suitable uses for wastewater. Possibilities for

using sewage sludge in the forestation and cultivation of exhausted and closed quarries and the forestation of

alvars were studied from 2002-2006. The results revealed that soil made from wastewater sludge complies with

the quality requirements set for products suitable as fertilisers. The soil made from sewage sludge is currently

widely used in landscaping. Using sludge compost as intermediate layers in Tallinn landfill is currently being

tested.

In the last 10 years, Tallinn has reduced the area of combined sewerage and built 100 km of new stormwater

drainage pipes, 33 km of them in the last three years. The total length of stormwater drainage pipes is 534 km.

The establishment of stormwater drainage pipes in combined sewerage areas has reduced the share of

stormwater flowing into the wastewater treatment plant and has improved the working regime and efficiency of

the plant. The biggest job in recent times was the establishment of the separate stormwater catchment area of

the Ülemiste junction (completed in 2013), Tartu Road and Sikupilli, where 22 km of stormwater drainage pipes

was built in total.

Figure 2. Stormwater drainage pipes in Tallinn

Construction of the stormwater drainage system of Ülemiste junction, which is designed to reduce the

stormwater impact load of the new junction on the sewerage pipelines, was completed in 2012. The pre-treated

stormwater from Ülemiste junction is directed to the historical Kadriorg Park, where it feeds the park’s canals.

The historical circular canal in front of Kadriorg Palace was reconstructed and stormwater facilities, a cascade

with five levels, a pond and stormwater outlet into the sea were built in the course of the reconstruction work

(Figure 1, Section 8B).

The principles of the stormwater system have also been implemented in the Life+ project Citywater, which

included the reconstruction in 2015 of the Lepiku ditch that runs from a nearby residential area to Tallinn

Botanical Gardens (Figure 3). The main goal of the reconstruction was to improve the quality of water in the

Lepiku ditch, which flows into Pirita River and which is located on a Natura 2000 site, via the implementation of

the principles of a sustainable urban drainage system. New habitats for water and shore plants, including

endangered and protected plants, were created in the course of the works and the area was landscaped.

Figure 3. Reconstructed Lepiku ditch

9C. Future Plans Describe the future short and long term objectives for waste water treatment and management and the proposed approach for their achievement. Emphasise to what extent plans are supported by commitments, budget allocations, and monitoring and performance evaluation schemes. Emphasise to what extent plans are triggered by the demands of EU and national regulations. Refer to:

1. Improvement / maintenance / management of collecting systems; 2. Improvement of connection to collecting systems (inter alia, additional % of p.e. forecasted to be

connected); 3. Improvement of design capacity, treatment level and treatment performance of UWWTPs ;indicate if

these go beyond the requirements in the Directive; 4. Improvement of connection to UWWTPs (inter alia, additional % of p.e. forecasted to be connected); 5. Improvements of further environmental and economic aspects of waste water treatment (e.g. removal of

micropollutants, pollution prevention, energy efficiency at UWWTPs, sludge treatment and disposal, treated waste water re-use , use of integrated constructed wetlands).

6. Other improvements (max. 800 words & 5 graphics, images or tables)

The main goal of Tallinn in the field of wastewater treatment is to reduce the pollution load directed from land

into the sea. This is done with the renewal of sewerage pipes, improving the work and efficiency of wastewater

treatment equipment and rebuilding combined sewerage into separate sewerage systems.

The following measures will be implemented in Tallinn in the coming five years, costing an estimated 90 million

euros:

1. Sewerage pipelines older than 60 years will be replaced in Tallinn by 2020. This will help to guarantee

the reliability of the city’s sewerage system and minimise the exploitation costs of the entire system (e.g.

reduction of infiltration in sewerage pipes). An analysis of break-downs and other deviations and an

assessment of the condition of the pipelines must be completed before replacement. 93 km of pipes will

be replaced by 2020.

The regions that will be reconstructed over a short period of time will be selected on the basis of the

share of older pipes that are more prone to break-downs. Another aspect that will be considered is the

reconstruction of a region’s water supply and sewerage pipelines at the same time in order to reduce

costs and the volume of road works.

2. Reconstruction of sewerage and stormwater pump stations will continue, as the present

technological systems and equipment are outdated and must be replaced.

3. Reconstruction of Paljassaare wastewater treatment plant will continue. The main emphasis is on

the replacement of old equipment and updating technology to guarantee uninterrupted technological

processes and the quality of output indicators. Investing in the improvement of the technology of the

treatment plant, especially in respect of phosphorus separation, and in increasing treatment capacity to

make it comply with the changing pollution load and the increasingly stricter treatment requirements is

important. The other large-scale works that are planned include replacement of the main pumps,

improvement of mechanical treatment (new sand trap unit) and further development of sludge handling.

4. Reconstruction of combined sewerage catchment areas into separate areas is continuing. The

necessary work project for the collector with the biggest catchment area (667 ha) in Tallinn (Seevaldi)is

due for completion. The second in line is turning the Vesse-Betooni catchment area, which covers the

Lasnamäe industrial area, into a separate system.

5. A snow-handling concept will be developed, as finding collection and handling sites for snow has

been a problem in winters with heavy snowfall. Separate collection sites will be established for freshly

fallen snow (so-called clean snow) and snow that has been on the ground for a longer period or where

snow control agents have already been used. The latter require the construction of special snow

depositing sites that have liquid-proof bottoms and are equipped with sand and oil traps.

Figure 1. Very snowy winter in Tallinn, 2009/2010

Constant work whose duration exceeds short-term goals:

1. Reconstruction of all combined sewerage systems into separate ones. The location of buildings and

streets complicates such work in the city centre, especially in the Old Town. The biggest challenge is

the construction of the stormwater drainage system of the Suur-Sõjamäe industrial region near Tallinn

Airport.

2. Installation of technical equipment that removes oil and oil products in the drainage systems of main

roads and car parks. While larger car parks (with over 50 parking spaces) have predominantly been

equipped with oil control systems, they have not yet been installed on main roads.

3. Organisation of campaigns to raise the awareness of the general public in relation to the increased use

in substances of household chemicals and industry that are toxic and impact on the efficiency of

wastewater treatment.

9D. References List supporting documentation, adding links where possible. Further detail may be requested during the clarification phase. Documentation should not be forwarded at this stage. (max. 400 words)

Citywater project – www.citywater.fi

Development Plan of Public Water Supply and Sewerage in Tallinn 2010-2021 –

https://oigusaktid.tallinn.ee/?id=3001&aktid=118953&fd=1&leht=1&q_sort=elex_akt.akt_vkp

Tallinn Environmental Protection Action Plan 2013-2018 –

https://oigusaktid.tallinn.ee/?id=3001&aktid=125983&fd=1&leht=1&q_sort=elex_akt.akt_vkp

Tallinn Environmental Strategy to 2030

https://oigusaktid.tallinn.ee/?id=3001&aktid=120867&fd=1&leht=1&q_sort=elex_akt.akt_vkp

Website of AS Tallinna Vesi – http://www.tallinnavesi.ee/en

Yearbooks of AS Tallinna Vesi – http://www.tallinnavesi.ee/et/Ettevote/Aruanded_ette/Keskkonnaaruanded