Summary:

The article presents evaluation of sewage treatment plant in Wadowice operation on the basis of pollutants’ reduction in the period from January 2003 to December 2005. Additional aim was analysing amount of inflowing sewage in the research period. Evaluation of operation capacity was based on reduction size of 5 chosen pollutants’ indexes: BOD₅, COD, total suspended solids, general nitrogen and general phosphorus. Values of above mentioned pollutants’ indexes in treated sewage were compared to values from water-law permission given by Wadowice Starost for Wadowice Waterworks and Sewerage Utility Sp. z o. o. from 28.03.2006. Results of analyses of treated sewage composition show, that mean values of BOD₅, COD, total suspended solids, general nitrogen and general phosphorus are lower than the admissible values from water-law permission. In the case of BOD₅ mean value on the outflow (14,0 mgO₂·dm^-3) is almost 7% lower than the admissible value (15 mgO₂·dm^-3), COD (mean value 89,15 mgO₂·dm^-3) – 28,7% lower than the admissible value (125 mgO₂·dm^-3), total suspended solids (mean value 27,27 mg·dm^-3) – 22,1% lower than the admissible value (35 mg·dm^-3), general nitrogen (mean value 22,17 mgNg_en·dm^-3) – 26,1% lower than the admissible value (30 mgNg_en·dm^-3) and general phosphorus (mean value 1,26 mgPg_en·dm^-3) – 37% lower than the admissible value. Mean BOD₅ reduction in the treatment process was 97,13%, COD – 90,56%, total suspended solids - 90,87% , general nitrogen– 52,73% and general phosphorus – 88,15%. Reduction of all analysed indexes except general nitrogen was on the level higher than guidelines given by the Ordinance from 31st July 2006. General nitrogen reduction on the level of 52,73% was lower than the normative one, but even though no case of transgression of admissible value was stated. The paper presents mean monthly inflows in analysed three years of research. In 2003 mean amount of inflowing sewage was 6 627 m³·d^-1, In 2004 6 615 m³·d^-1 flew in and in 2005 6 995 m³·d^-1 flew in. Although annual average inflows were lower than the admissible value (8 430 m³·d^-1), some months occurred in the research period when the inflow was higher than the assumed one. Presently, modernisation of the object lasts, aiming at increasing its capacity, so that it is possible to collect sewage from next canalised towns.