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.
The aim of the study was to assess the applicability of asymptotic functions for determining the value of CN parameter as a function of precipitation depth in mountain and upland catchments. The analyses were carried out in two catchments: the Rudawa, left tributary of the Vistula, and the Kamienica, right tributary of the Dunajec. The input material included data on precipitation and flows for a multi-year period 1980–2012, obtained from IMGW PIB in Warsaw. Two models were used to determine empirical values of CNobs parameter as a function of precipitation depth: standard Hawkins model and 2-CN model allowing for a heterogeneous nature of a catchment area.
The study analyses confirmed that asymptotic functions properly described P-CNobs relationship for the entire range of precipitation variability. In the case of high rainfalls, CNobs remained above or below the commonly accepted average antecedent moisture conditions AMCII. The study calculations indicated that the runoff amount calculated according to the original SCS-CN method might be underestimated, and this could adversely affect the values of design flows required for the design of hydraulic engineering projects. In catchments with heterogeneous land cover, the results of CNobs were more accurate when 2-CN model was used instead of the standard Hawkins model. 2-CN model is more precise in accounting for differences in runoff formation depending on retention capacity of the substrate. It was also demonstrated that the commonly accepted initial abstraction coefficient λ = 0.20 yielded too big initial loss of precipitation in the analyzed catchments and, therefore, the computed direct runoff was underestimated. The best results were obtained for λ = 0.05.
The paper presents the results of the analysis concerning the verification of the actual hydraulic load and the load of organic pollutants compared to the conditions designed for 4 household wastewater treatment plants. The researches were carried out in the annual period from May 2015 to April 2016. Based on the conducted analysis, it was found that objects act as underloaded hydraulically and the actual inflow of sewage to the analysed objects during the research period ranged from 7.3% to 32.7% in relation to the inflow assumed in the project. Furthermore, in the case of loading the treatment plant with the load of pollutants expressed as PE, it was fund that the actual PE values were lower than assumed in the project. Therefore, it is important that the sizes of the series of household sewage treatment plants were selected depending on the individual conditions of household, i.e. the number of inhabitants or the amount of consumed water.