This paper presents the changes in concentration of seven biogenic indices in the Wisłok River water and determines the water treatment processes required in order to obtain water fit for consumption. The investigations were conducted during 2004–2013, and water samples were collected at a measuring-control point was situated at 67.9 km on the river at the surface water intake for the water supply to the Rzeszów city dwellers. Analysis of the research results allows for the forecasting of technological and organizational changes in the treatment processes of the abstracted water. It was found that only the mean concentration of Kjeldahl nitrogen exceeded the value admissible for class I, which allowed the Wisłok River water to be classified as class II with good potential and determined the water quality category as A2, which indicates the necessity for typical performance physical and chemical treatment. Downward trends in the contents of the tested nutrients occurred during the period of investigation, except for nitrite nitrogen. Statistically significant downward trends were registered for ammonium nitrogen, Kjeldahl nitrogen, total nitrogen and phosphates. The decline in nutrient concentrations in the water of Wisłok is a tangible result of the introduction of new standards of water resource management in the catchment, compliant with the European Union legislation.

Spatial and time changeability of surface water quality results from anthropogenic activities in the catchment area [1,2], growing pollutant amount [3], and environmental management [4]. The EU Water Framework Directive (WFD) [5] stipulates that the waters of all European strongly changed water bodies must achieve good ecological potential and good chemical status by 2015 [6, 7]. A considerable part of waters bodies in Europe is exposed to the risk of not achieving a good state by this year [8]. Therefore, water quality assessment and determining the factors affecting its changes have been the subject of numerous papers [9][10][11][12][13][14][15][16]. The assessment process faces two main problems: complexity and uncertainty [17] -both due to high social and economic costs [6,18]. Changeability of water chemical parameters should be assessed on the basis of monitoring programs in order to detect changes in their quality status [6,19,20]. This aims to determine the main actions targeting restoration of good status of waters, which ensures that their quality would respond to the aims suggested by WFD for the human population, considering the principle of sustainable development and public health [21,22]. Problems with water quality are associated with a great number of nutrients originating from surface runoff from urban areas [23] (including sewage discharge) [2, 24] and from agricultural areas [7,25].Pol. J. Environ. Stud. Vol. 24, No. 4 (2015), [1633][1634][1635][1636][1637][1638][1639][1640] Original Research Changeability of Oxygen and Biogenic Indices in Waters Flowing through Areas under Various AnthropopressuresWłodzimierz Kanownik*, Agnieszka Policht-Latawiec AbstractSeasonal and monthly changes of biogenic and oxygen indices in the water of two streams in 2007-10 are discussed in this paper. The streams have similar catchment areas that area managed and used in different ways. The Krzyworzeka stream catchment is covered by rural areas, whereas the Serafa stream flows through built-up and urbanized areas.Statistical testing using U Mann-Whitney's nonparametric test was conducted to determine the differences of oxygen and biogenic water quality index values between the growing season and outside the growing season. Statistically significant decreases in ammonium, nitrate, and total nitrogen concentrations, as well as oxygen dissolved in Krzyworzeka Stream, were registered during the growing season. In the Serafa water only the concentrations of dissolved oxygen and biological oxygen demand decreased significantly. On this basis it was established that in clean waters vegetation development considerably influences the content of biogenic compounds. Serious pollution of stream water causes vegetation and the intensity of biochemical processes in water to not cause any clear reduction in biogenic compound concentrations.

The paper presents an analysis of 20 physicochemical elements in the Bobrza River water sampled above and below the treated sewage discharge point. Sitkówka mechanical and biological sewage treatment plant with a value of 289 000 People Equivalent discharges on average 51 000 m 3 of treated sewage daily, which makes up 29% of mean daily flow in the Bobrza River. On the basis of hydrochemical analyses it was stated that the discharge of treated sewage led to worsening of 18 out of 20 studied water quality indices in the Bobrza River. In the river water below the sewage discharge statistically significantly higher values of electrolytic conductivity, dissolved solids, calcium, magnesium, sodium and potassium were registered. A decrease in dissolved oxygen content in the water and increase in its electrolytic conductivity caused a change of water quality class in the Bobrza River from the maximum potential to potential below good. On the other hand, increase in concentrations of dissolved solids and sulphates caused a change of the water class from the maximum potential to good potential. Statistical factor analysis (FA) made possible a reduction of a set of 20 physicochemical elements to four mutually orthogonal factors explaining 95% (above the treatment plant) and 96% (below the treatment plant) of the internal structure of primary data. The first factor is connected with point source pollution (sewage discharge), the second describes oxygen conditions in water, the third results from seasonality and is responsible for the pollutants from natural sources, whereas the fourth factor has not been unanimously defined yet.

The paper presents changes in the contents of physicochemical indices of the Sudół stream water caused by a discharge of purified municipal sewage from a small mechanical-biological treatment plant with throughput of 300 m3·d−1 and a population equivalent (p.e.) – 1,250 people. The discharge of purified sewage caused a worsening of the stream water quality. Most of the studied indices values increased in water below the treatment plant. Almost a 100-fold increase in ammonium nitrogen, 17-fold increase in phosphate concentrations and 12-fold raise in BOD5 concentrations were registered. Due to high values of these indices, the water physicochemical state was below good. Statistical analysis revealed a considerable effect of the purified sewage discharge on the stream water physicochemical state. A statistically significant increase in 10 indices values (BOD5, COD-Mn, EC, TDS, Cl−, Na+, K+, PO43−, N-NH4+ and N-NO2) as well as significant decline in the degree of water saturation with oxygen were noted below the sewage treatment plant. On the other hand, no statistically significant differences between the water indices values were registered between the measurement points localised 150 and 1,000 m below the purified sewage discharge. It evidences a slow process of the stream water self-purification caused by an excessive loading with pollutants originating from the purified sewage discharge.

Surface waters may be polluted by substances originating from anthropogenic sources [Grochowska and Tandyrak 2007, Bojakowska et al. 2010, Húska et al. 2013] and due to natural processes occurring in the environment [Moniewski and Stolarska 2007]. Natural sources may comprise various pollutant agents, such as plant remnants and humus substances, clay and silt particles of soils or rocks, compounds of iron and manganese, etc. However, pollution caused by various human activities is far more dangerous to the environment [Dąbrowska 2008, Policht-Latawiec and Kanownik 2013]. These may be either liquid or gaseous substances. They find