Summary:

The article presents results of analysis and their discussion concerning operation of sewage from butchery of pigs pretreatment plant in Gruszów in Pałecznica commune. Additionally, construction of the mentioned pretreatment plant was discussed, for authors of its idea and project are Ph.D. eng. Marian Długosz and Ph.D. eng. Piotr Bugajski. The aim was to solve three problems: to regulate high disproportion of outflowing sewage, to reduce amount of pollutants contained in sewage and to prevent them from rotting. The research included regulation of sewage outflow put evenly in time, physicochemical analysis (BOD₅ and COD) of sewage before and after pretreatment plant and measurements of oxygen amount in outflowing sewage. The first object on the technological way is well with the sieve for solid parts, in which pollutants bigger than 5,0 mm are stopped. Next, sewage flows into the settling tank, in which inflammable pollutants sediment to the bottom, and afterwards sewage flows to the aeration chamber. In this chamber, process of sewage aeration (oxygenation) occurs. Oxygenated sewage flow into the grease trap, and next into the well, in which sewage separation occurs. Part of them goes into the living sewerage system, and next to the Bioblok PS-50 sewage treatment plant, and part of then is turned back (recirculated) into the settling tank. On the basis of the analysis of research and observation results it has been ascertained that the post-slaughter sewage from butchery of pigs pretreatment plant fulfills its tasks. Namely, regular sewage outflow put evenly in longer period of time was obtained. Irregular inflow of sewage was one of the main reasons for disruption of collective Bioblok PS-50 treatment plant’s operation. Second main problem which was solved, was reduction of amount of inflowing pollutants, showed by indexes: BOD₅ and COD. As a result of sewage pretreatment processes, pollutants reduction about 36% for BOD₅ and 37% for COD was obtained. It let obtain values of these two indexes on the level allotted in Ordinance given by Borough Office in Palecznica, which is an owner of Bioblok PS-50 sewage treatment plant in Gruszów. The aeration system and partly recirculation of sewage caused, that it was outflowing “fresh”, not rotten. In sewage outflowing to the collective sewerage system, amount of oxygen oscillated around 2,0 mgO₂·dm^-3. Minor, but also important factors, influencing conditions’ improvement of sewage treatment in collective treatment plant, are reducing amount of grease outflowing from animals’ butchery.