Summary:

The aim of the research was defining temperature changes of sewage in sewerage system and in open biological reactor under the influence of atmospheric air temperature. The literature connected with sewage treatment doesn’t give unequivocal information regarding influence of air temperature on sewage temperature in the canalisation. Some authors claim that such a relationship doesn’t occur. The research carried out on the area of sewage treatment plant in Koszyce commune showed, that important relationship exists between mean daily atmospheric air temperature (tair) and mean daily temperature of sewage in sewerage system (t_sew). This relationship may be with high accuracy (R²=0,78, p<0,001)described by a cubic polynomial equation: t_sew = -0,0011·(t_air)³ + 0,0232·(t_air)² + 0,3704·t_air + 9,0554. In the research period, mean daily temperature of sewage in sewerage system was going under big fluctuations, from 6,35 to 17,56°C. Changes of sewage temperature in the collector during the day ranged between 0,35°C and 4,60°C. In the winter period, with mean daily air temperature under 5°C, sewage temperature in the canalisation lowered under 10°C, reaching its minimal value of 5,37°C. In biological reactor, which was built as a reinforced concrete open reservoir, mean daily sewage temperature ranged between 5,68 and 21,04°C. Whereas in the winter period (December, January, February) sewage temperature in the reactor lowered under 10°C, reaching its minimal value of 5,32°C. This temperature is definitely too low for needs of biological process of biogenic compounds’ removal. The carried out research proved the influence of mean daily air temperature, higher than 5°C, on sewage temperature in an open biological reactor. With air temperature lower than 5°C, sewage temperature in the reactor is shaped by the temperature of sewage which flows in from the sewerage system.