This paper describes the development of waste water purification systems in Gdansk from the beginning of the 19thcentury up to now. The operating conditions of the sewage plants are also presented and illustrated with flowsheets.From the beginning the sewerage system in Gdansk was decentralised. Each of the three sewerage subsystems existingat the beginning of the 20th century had its own local treatment plant.The first waste water treatment plant “Stogi,” using filtration fields, was built in 1872 and it fulfilled its role efficientlyfor almost 120 years before it was closed in 1991. In 1932 an activated sludge plant “Zaspa” was built in order to replacetwo smaller local plants using the technology of filtration fields and biofilters. Later developments of the seweragesystem aimed at centralisation just as much as they do today. The central mechanical treatment plant “Wschod” with atotal flow of 180,000 m3/d was constructed in 1976. Chemical treatment to remove pollutants more effectively was notintroduced until 1993. By the middle of 1999 the plant will treat all waste water using the modified UCT2 system forbiological nutrient removal.INTRODUCTIONGdansk is a thousand-year-old city with a rich mercantiletradition that can be traced back to the Middle Ages. Thanksto its geographical location the city has been an importantland and sea port for centuries. Today it is Poland’s biggest seaport and an important communication centre.Gdansk is situated on the coast of Gdansk Bay at themouths of the Vistula River and occupies an area of 262 km2with 460,000 inhabitants. Gdansk is a part of a largemetropolitan area called “Tri-city,” which includes Gdyniaand Sopot. This metropolitan area has a population of760,000 and it covers an area of 415 km2. Each city has aseparate water supply system. Gdansk and Gdynia have theirown sewerage systems. Waste water from Sopot is directed toGdansk. Such a high concentration of people and industryhas a significant impact on the sea, above all on the Bay ofGdansk.The Vistula River carries about 30 km3 of water per yearfrom a vast catchment area of 194,424 km2, which covers mostof Poland. There are about 50,000 sources of waste water thatpollute directly or indirectly the river. Approximately 34% ofthe total amount of municipal sewage produced in the Vistulacatchment area, where twenty-six million people live, gets tothe rivers without any purification [13].Gdansk Bay is a shallow water basin, which is separatedfrom the sea by the Hel Peninsula. This limits the refreshingof sea water in Gdansk Bay, i.e. the exchange of water with theBaltic Sea.In the 19th century Gdansk (Danzig) was an importantmilitary harbour in the Kingdom of Prussia. In 1875 it had98,000 inhabitants [16]. The population grew rapidly, butaccording to the statistics in 1851-1855 the death rate wasvery high, 4.5 per cent. Until the 1870s the death rateexceeded the birth rate, primarily as a result of deficiencies inthe water supply system [1, 4, 16].Small amounts of clear spring water were delivered to thecity with the help of horse carts. However, it was veryexpensive and could be bought only by the rich. Most citizensused water from wells or simply from the Radunia River,which flows through the city. Water from the river wasdelivered to some parts of the city by means of wooden pipesdating even from the Middle Ages [1]. The very same riveralso played the role of sewage receiving body. Waste waterfrom households was collected in buckets and dumped intoditches constructed along the main streets. It flowed bygravity outside the city or to the rivers within the city. Henceepidemics were common and threatened the visitors of thecity [1].Obviously, one of the most important issues for thecitizens of Gdansk was the supplying of clear drinkable water.In 1869 the first groundwater intake “Pregowo” was built.Raw groundwater was taken from high morainic hills at 110m above sea level and fourteen kilometres from the city. It wastransported to the city by a pressure pipe with a diameter of418 mm. The average water production was 10,400 m3/d andno treatment was needed [1, 2, 6]. Supplied water was notbacteriologically contaminated.There was an obvious need for developing the seweragesystem as well. The first steps in developing waste waterpurification were also taken early at about the same time thewater supply system was begun [16, 4].请点击图标下载浏览：附件
