Collection of wastewater
To ensure an uninterrupted collection and discharge of wastewater, we preventively flush the wastewater network, as well as reconstruct and extend the sewerage and storm water network.
Cleaning and maintenance of the wastewater network
Our attention continues to be on the risks related to potential floodings and pollution. 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. Water consumption has constantly been decreasing over the recent years, resulting in the reduction of flow volumes and flow speeds. Initially, the pipelines were dimensioned for larger flow volumes. This in turn increases the risk of blockages. Additionally, continuous extension of sewerage network is affecting the total number of blockages.
In 2014, the level of wastewater discharge service and blockages remained similar to two previous years, only the number of blockages dropped slightly by 17 blockages, compared to 2013. This kind of continuously good performance over the last years has been the result of numerous preventive actions, such as raising the efficiency of pressure washing. Also, renovating the problematic pipes in the framework of 5+5 programme contributes to this. 5+5 programme means that according to the Services Agreement, signed with the City of Tallinn, we will renovate each year 5 kilometers of sewerage network and 5 kilometers of water network.
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. Pressure washing is performed by our subsidiary OÜ Watercom using a recycling system on the trucks, which enables to use the water required for flushing repeatedly.
Reconstruction and extension of the wastewater network
Investments in the replacement of worn out wastewater network and in the construction of new network contribute to the consistent improvement of the quality of environmentally friendly service.
In 2014, the company renovated 5km of the existing wastewater network. As per the agreement with the City of Tallinn and pursuant to the European Union wastewater collection directive, we have completed the public water supply and wastewater network extension programme. Therefore, the respective data is not included in this report.
Monitoring overpollution caused by customers
In order to ensure acceptable concentrations of pollution in the 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 with legal requirements. Information on the average pollution indicators of major industries is also regularly submitted to the Environmental Board.
In 2014, our Wastewater Inspectorate performed 665 inspections to identify inspection wells, to check local treatment facilities and boundary drawings. 1,404 wastewater samples, incl. 489 monitoring samples, were taken for determining the wastewater pollution load at sites. Over-pollution instances were identified and over-pollution fees were applied on 391 occasions.
Storm water outlets
In 2014, ASTV Wastewater Inspectorate monitored 24 storm water outlets pursuant to the requirements set forth in the permits for a special use of water no L.VV/322982 and L.VV/320980, the largest storm water outlets being the Lasnamäe, Harku and Mustoja outlets. Four storm water outlets (Olevi, Kaare, Raba and Vabaduse streets) have been equipped with local treatment facilities such as sand and oil traps, which we regularly maintain and clean in order to avoid possible environment pollution.
A total of 4.08 million m3 of storm water was discharged to the environment through the outlets in 2014, i.e. less than a year before. This was due to the lower volume of precipitation during the reported period. The average level of precipitation in Tallinn was 587 mm per area unit in 2013, in 2014 this figure was 576 mm. Though the amount of precipitation was low in 2013 too, there were more pouring rains that quickly flushed the pipelines, and this caused significantly smaller amount of suspended solids in storm water. While in 2014, there were less pouring rains and the amount of suspended solids were on average level. At the same time, the amount of oil products in storm water was higher in 2014, due to a one-time oil products discharge into the storm water network and on to the sea, from an unknown source. As a responsible company, we have tried to identify this source of pollution, unfortunately without any success. In order to avoid similar situations in the future, we intensify cooperation with Tallinn Municipal Police and educate our consumers through media campaigns.
