Restoration of Urban Waters in St. Petersburg: Social, Technical and Financial Aspects

Abstract

Introduction St. Petersburg is located at the mouth of the Neva River and across the islands of its delta on the coast of the Finnish Gulf of the Baltic Sea. The territory of the city is 606 square kilometres. The population of St. Petersburg is 4 780 000 inhabitants. St. Petersburg, due to its own unique architecture and beautiful suburbs with the world famous palace and parks, is recognised as a cultural capital of Russia. In 2003 St. Petersburg has marked three hundred years since its foundation. The city is located on 42 islands. The main water bodies in the city include the Neva estuary, the Neva River with its tributaries and branches, other rivers and channels, natural and artificial lakes and reservoirs, and marshes. There are 64 streams, 48 channels and 34 brooks in St. Petersburg and its suburbs. Within the city, there are more than 130 reservoirs with the water surface area greater than 1 ha. The characteristics of basic streams are given in Table 1. St. Petersburg is obviously one of the cities of the world with the greatest abundance of water. Almost 20 % of the city territory is covered with water. If the Neva estuary (serving now as a city reservoir) in the Finnish gulf were included in the city area, the share of the water surface would represent 50% of the city area. St. Petersburg is subject to flooding. Catastrophic floods occurred in 1824 and 1924, when the level of water rose above the mean level by 4.2 and 3.7 m, respectively. The highest point of Vasilievsky Island has an elevation 3.80 m, Petrogradsky Island 3.40 m. For protection of the city against floods, a dam was constructed along the western boundary of the Neva mouth. Eventually, a complex of flood protection structures will stretch through the entire Neva estuary from the south to the north, over a length of 25.4 km, including a section of 22.2 km over water. The structure will consist of 11 rockfill/earthen dams, with six openings for flow of water and two for ship passage. The main river is the Neva, with an average discharge of 2,500 m3 /s. The Neva is a source of drinking water supply to St. Petersburg. Municipal wastewater is treated and the treated effluent is discharged into the Neva estuary in the Finnish gulf. The area of the estuary is 329 km2 , with prevailing depths of 3 -5 m. TABELA1. - Sewer system on two thirds of the city territory is combined and the remaining part is served by a separate system. Currently, long-term development, construction and reconstruction of the sewer system are nearing completion. About 70% of wastewater from the city is subject to full biological treatment. By 2005, up to 80% of wastewater from the combined sewer area will be treated, and the treatment of all wastewater is planned by 2015. Reaching this ambitious goal will require large investments, material resources and hard work. It will be necessary to construct major intercepting tunnel collectors, connect to them sewers conveying untreated wastewater, reconstruct sewer network, and build a new facility for sewage sludge incineration. The condition of urban waters is an objective indicator of the degree of pollution of the environment. The natural processes of water quality and functioning of aquatic ecosystems in urban areas are generally disturbed because of a high level of anthropogenic pollution loading and low self-purification of urban streams and reservoirs. The poor quality of water negatively influences aquatic life and the health of urban dwellers. Effective operation of urban aeration facilities and construction of local wastewater treatment plants (WWTPs) by the city during the 1980s and some reduction in the share of industrial wastewater in total wastewater flow have ensured some recovery of the quality of the Neva River and the Neva estuary during the 1990s. Ecological conditions in these water bodies have stabilised.