Summary:

The performed study aimed to determine the effect of sewage temperature in bioreactors on pollution discharges measured by the BOD5, COD and total ni-trogen indexes. The research was carried out in a municipal sequential batch re-actor (SBR) treatment plant. The discussed treatment plant is located in Książ Wielki commune in Miechów district in Lesser Poland voivodeship. Households from two villages: Książ Wielki and Wielka Wieś discharge their sewage into the analysed treatment plant. An average of 100 to 110 m3•d-1 of sewage constituting nearly 50% of the designed hydraulic load of this object was discharged into the treatment plant during the study period. Temperature measurements and sewage sampling for physicochemical analyses were performed for 24 months in 2007 and 2008. Twenty four sewage samples were collected with a frequency of once per month. The lowest sewage temperature in the bioreactor during the study period was 7.1°C, whereas the highest temperature reached 18.8°C. Therefore, the sew-age temperature amplitude in the bioreactor was 11.7°C. Low sewage temperature below 10°C occurred from December to April. Lower efficiency of neutralisation of the 3 analysed pollution indexes was observed in this period. The carried out research revealed average relationship between the sewage temperature in the bioreactor and values of oxygen indices: BOD5 and COD. Based on the regression equation, it was found that with a 1°C increase of sewage temperature the values of BOD5 decreased by 0.64 mg•dm-3 and values of COD decreased by 1.76 mg•dm-3. There is a high correlation between sewage temperature in the bioreactor and amount of total nitrogen in the sewage discharged from the discussed treatment plant. Together with 1°C increase of sewage temperature in the bioreactor amount of total nitrogen decreased by 1.34 mg•dm-3. Two oxygen indices included in evaluation of the discussed object operation - BOD5 and COD - did not exceed the admissible values described in the water-law permission.