Over the last 35 years the city of St. Petersburg has come a long way in its wastewater treatment systems. Up until 1978, all wastewater was drained directly into the Neva and the Gulf of Finland, i.e. into the Baltic Sea. South West Wastewater Treatment plant (ie Vodokanal) of St. Petersburg currently treats 98.4% of all wastewater. This became possible thanks to the completion of the large scale project on the construction of the Main Sewage Collector marked with the ceremony held on the 10th of October 2013. Notably, the project was completed in the year that was announced the “Environmental Protection Year” in Russia. Moreover, the 155th anniversary of Vodokanal St. Petersburg fell on October, 10.
The Main Sewage Collector Extension is a complex system of engineering facilities. It consists of:
- two 4m diameter tunnels, 12.2 km each, laid at the depth of 40-90m;
- 8 microtunnels with a total length of over 7.600 km;
- 64 shafts, 6-9m diameter each, at the depth of 10 to 80m;
- 5.2 km of street sewerage networks, 0.25-1.2m in diameter;
- Flow controller – a high-capacity pumping station installed in a 90m deep, 24 m diameter shaft.
With the Collector in place, 73 direct wastewater discharges were closed and 284 thousand m3/day of untreated wastewater were no longer discharged into the Neva. This means nearly 103 million cubic meters of wastewater per year; previously, it all ended up in the Neva and the Gulf of Finland.
Wastewater treatment is implemented at Vodokanal’s treatment plants in accordance with Russian and international standards. Currently, St. Petersburg fully meets the recommendations of the Baltic Marine Environment Protection Commission (HELCOM). Concentrations of phosphorus in the total volume of wastewater discharge do not exceed 0.5 mg per liter, nitrogen – 10 mg per liter (phosphorus and nitrogen trigger the growth of blue-green algae which are the main threat to the health of the Baltic Sea)
Wastewater treatment is implemented at 15 municipal treatment plants, including the Central and Northern Aeration Stations and the South-Eastern treatment facilities.
The completion of South-Eastern treatment facilities construction in 2005 was a large scale investment project that signified international cooperation in the fields of environment protection and finance. A large number of companies were involved in its implementation. With this project, the public-private partnership scheme was applied in Russia for the first time. The project has received support from Nordic governments, international financial institutions and donor organisations.
St. Petersburg was the first megapolis in the world to find a solution to the sludge disposal problem (sludge forms as a result of water treatment): there are currently three sludge incineration plants in operation built by Vodokanal. The incineration process turns sludge into odorless non-hazardous ash and generates heat and electric power.
Vodokanal uses bio-indicators such as Australian red-claw crayfish to maintain the quality of treated effluent, and giant snails to control the composition of flue gases emitted from sludge incineration plants.
According to official data on nutrient inputs to the Baltic Sea provided by Vodokanal of St. Petersburg, over the last 35 years the amount of phosphorus discharged annually reduced from 3,973 tons in 1978 to 433 tons in 2013. Similarly, nitrogen discharge reduced by almost a half, dropping to 9,303 tons of nitrogen annually in 2013 compared to 23,175 tons in 1978.