The paper presents an analysis of hydraulic load in a wastewater treatment plant (WTP) in Jasło. The study was based on the records of daily sewage volume entering the treatment plant within a multi-year period of 2010–2014. The analysis took into account the average daily amount of incoming sewage, the maximum daily peaking factor for the incoming sewage, changes in the sewage volume depending on specific month and day of a week, and class intervals with the greatest frequency of occurrence. The analysis revealed that the average daily volume of the sewage entering the WTP in Jasło in the investigated multi-year period was 13 045 m3·d−1. The amount of incoming sewage was variable, as evidenced by the maximum peaking factors of daily sewage inflow that ranged from 1.07 to 2.78, depending on a specific month. The sewage admission was the largest in March, May and June and on Saturdays. Sewage volume interval most often occurring at the WTP in Jasło was the one between 8 000 and 10 000 m3·d−1. The study results indicated that the facility was hydraulically underloaded.

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The paper discusses technological reliability of a collective wastewater treatment plant (WTP). The WTP capacity expressed as population equivalents (PE) was 22,500. The research was conducted in 2013 and 2014 and it involved the collection and physical and chemical analysis of 101 samples of raw and treated sewage. Reliability analysis was based on Weibull reliability theory. Reliability of retaining organic compounds defined as BOD 5 was 68%, and for biogenic compounds, such as total nitrogen and total phosphorus, it was 92% and 88%, respectively.

The study provides a comparative analysis of the quality of sewage discharged from selected sewerage systems. The analyzed data were collected from 10 agglomeration sewerage systems discharging sewage into collective wastewater treatment plants (WTP). The investigated pollution indicators included BOD5, CODCr, total suspended solids and biogenic indicators such as total nitrogen and total phosphorus. These results were compared with the outcomes reported in commonly available research papers on sewage disposal. Considering the concentration of individual pollution indicators, more detailed categories of sewage pollution were adopted in this work. The sewage was divided into five basic groups: I – highly concentrated, II – concentrated, III – moderately concentrated, IV – diluted, and V – highly diluted. The sewage categories accounted for the following pollution indicators: BOD5, CODCr, total suspended solids, total phosphorus and total nitrogen. Mean BOD5, CODCr and total suspended solids in raw sewage were higher than average values reported in the referenced literature. Contrary to that, concentration of total phosphorus in raw sewage was significantly lower than reported by other authors. The outcomes of this study suggest that the predictions concerning pollution degree of raw sewage made at WTP design stage should not be based exclusively on general values provided in literature reports.

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Nutrient removal is a very important criterion in household sewage treatment systems. The process of sewage treatment must ensure an adequate degree of nutrient reduction from raw sewage, both in municipal treatment plants and in small treatment plants, below 50 PE [1]. The use of membrane bioreactors (MBR) in the treatment of wastewater is limited to small objects with relatively small organic pollutant load.

The effectiveness of removing indicator bacteria from domestic sewage using a vertical flow filter filled with natural materials has been analysed. The count of Escherichia coli and coliform bacteria was measured in raw and treated sewage and effectiveness of their removal under variable conditions of hydraulic load and depending on the filter filling (type, size and filling proportions) was assessed. A single-layer sand or zeolite filter was the most effective in reducing bacterial contamination. The sand-filled filter allowed the removal of 99.993-99.997% of Escherichia coli and the one filled with fine zeolite of 99.995%. The principal component analysis was used to comprehensively evaluate the filter performance. Three principal components were identified and they were responsible for 81% of raw data variability. The effectiveness of indicator bacteria removal depended mainly on the filling grain size and did not on filling proportions or its type.

The article evaluates the effectiveness of the removal of organic pollutants—nitrogen and phosphorus—from household sewage in a hybrid bioreactor with a submerged fixed bed. The experiment was carried out in two exploitation variants that were both conducted in a laboratory model of the hybrid bioreactor: (I) cycles of 120 min of aeration and 60 min of no aeration with a constant sewage dosage, and (II) cycles 60 min of aeration and 60 min of no aeration, with a periodic sewage dosage in the no-aeration phase. The experiment was carried out on real sewage primarily treated in a septic tank. The amount of pollution removal was calculated and compared with the mandatory standards according to Polish law. Moreover, the susceptibility of the sewage to the biological treatment, nitrification, and denitrification activity was determined. The research shows a higher effectiveness for the 60/60 model in comparison to the 120/60 model. High operation efficiency was observed regarding the removal of organic pollution and nitrate nitrogen. The tested structure showed very low nitrification activity combined with intense denitrification. These processes were observed in the 60/60 variant. The structure was often overloaded with the nitrate nitrogen, which was considered to be the nitrification process inhibitor. It was suggested that phosphorus was also removed by the denitrifying bacteria.