The effects of sewage treatment by a municipal sewage treatment plant were studied in Biała Podlaska. The object of study is a typical mechanical-biological sewage treatment plant with active deposit, receiving municipal and industrial sewage from Biała Podlaska and its surroundings. The plant has been designed to receive 13 500 m³ of sewage per 24 hours. At present the effective amount of the sewage treated is 11 000 m³ per 24 hours. In 2001 the mean efficiency of pollutant removal was the following: BOD₅ – 98.7%, COD_Cr – 95.4%, total suspended solids – 94.8%, total nitrogen – 81.7%, ammonium nitrogen – 98.3%, and total phosphorus – 91.5%. The results show that the sewage treatment plant in Biała Podlaska performs well which makes it possible to minimise a negative effect of sewage on the environment. The plant is an example of good design that may be followed in other objects of this type.

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