Wastewater Collection

Wastewater network and collection of wastewater

Wastewater is directed to the wastewater treatment plant by using the combined sewer system, which collects both sewerage and storm water. Some parts of our service area are also covered with a separate storm water system with storm water outlets. However, most of the storm water is collected with a combined sewer system and ends up at the wastewater treatment plant in Paljassaare.

The number of blockages is an indicator reflecting the condition of the wastewater network. Blockages are mainly caused by the sediments build-up in the wastewater network. Initially, the pipelines were dimensioned for larger flow volumes, so today’s smaller water consumption results in the reduction of flow volumes and flow speeds, which in turn increases the risk of blockages. Additionally, continuous extension of sewerage network is affecting the total number of blockages.

We have been able to achieve evenly good level of blockages in recent years due to many preventive actions, such as arranging preventive flushing of the pipelines. For flushing a pipe, first, a flow speed is generated with high pressure carrying sediment into the nearest cesspool. Sediment is then collected with pressure washing trucks and transported to Paljassaare Wastewater Treatment Plant.

In addition, each year the Company rehabilitates at least 5 km of problematic wastewater pipelines, which also facilitates effective wastewater collection.

Pollution load in wastewater and storm water

In order to ensure acceptable pollution load in wastewater reaching the Paljassaare Wastewater Treatment Plant we regularly monitor the wastewater discharged in Tallinn and Maardu and in the surrounding areas and check the compliance of pollution parameters with legal requirements. Information on the average pollution indicators of major industries is also regularly submitted to the Environmental Board.

In 2015, our Wastewater Inspectorate performed 672 inspections to identify inspection wells, to check local treatment facilities and boundary drawings. 1,417 wastewater samples, incl. 488 monitoring samples were taken for determining the wastewater pollution load at sites. Over-pollution instances were identified and over-pollution fees were applied on 407 occasions.

The average level of precipitation in Tallinn was 590 mm per area unit in 2015, which is slightly more than in 2014 when this figure was 576 mm. Consequently, the amount of storm water discharged to the environment through storm water outlets slightly increased in 2015, too.

Pursuant to the requirements set forth in the permits for a special use of water we monitor 24 storm water outlets, the largest among them being the Lasnamäe, Harku and Mustoja outlets. Four storm water outlets (in Olevi, Kaare, Raba and Vabaduse Streets) have been equipped with sand and oil traps, which we regularly maintain.