INSTRODUCTIONWhen determining the impact of a sewage treatment plant on particular elements of an aqueous environment, it is often improperly assumed that the receiver waters are mixed with purified sewage at the point of discharge or not far from that site. The route of total mixing of pollutants with receiver waters may be several hundred times longer than the width of the riverbed. In fact, the total mixing of wastewater with receiver waters does not always occur at a short distance from the discharge. Determining the distance, at which full mixing should be considered in a given river cross-section in vertical and transverse dimensions [Rutherford, 1994, Miakoto, 2005. Determining the distribution of pollutants within the mixing zone is essential to understand the impact of purified wastewater on aquatic organisms, fish migration, and the health of people using the surface water. Due to this, it is also possible to simulate changes in the quality of river water and to obtain information on the possibility of discharging the purified sewage to surface waters. When forecasting changes in surface water quality, it is very important to learn the concentration distribution within the mixing zone because a large area of excessive concentration of harmful and hazardous components can be found within it. This would result in a reduction in water intake for utility purposes and disturbance of habitats responsible for biodiversity conservation [Adamski, 2000, Ostroumov, 2004, Miakoto, 2005.Mixing of wastewater with receiver waters is possible due to the advection and turbulent and molecular diffusion. The result of these processes is balancing the concentrations of wastewater constituents in the whole volume of water [Ru- Research Article ABSTRACT Discharges from wastewater treatment are among the key sources of pollution, if norms included in the applied legal acts are exceeded. In determining the impact of these objects on water environment it is often assumed that complete mixing wastewater with surface water is in the point or close to the discharge. In fact, the complete mixing of waste water in a short distance from the discharge occurs incidentally depending on the type of sewage receiver. The size and type of specific sewage receiver determines the conditions of self-purification. Complete mixing zone has a huge impact on the intensity of self-purification processes. Therefore, the possibility to determine the size zone of complete mixing of the waste water from the water receiver is important. The issue involves a series of methods, the most computational, which more or less allows to evaluate the distance of mixing waste water. advection, turbulent and molecular diffusion affect mixing wastewater with surface waters. The article discusses the factors influencing the mixing process and the impact of mixing on the self-purification surface waters. The aim of the article is a review of several methods for determining the distance of the segment mix completely discharged wastewater, with regard to the location o...

The aim of the work was to analyze the content of Ni, Pb and Cd in organs (root, stem, leaf) Typha latifolia L. and Nuphar lutea as well as bottom sediments of the Ełk River and selected tributaries. An attempt was also made to indicate the factors and processes governing the behavior of the investigated metals in the water environment of the examined rivers. The research object was the Ełk River with its three tributaries-the Gawlik River, the Binduga River and the Kuwasy Canal. Samples of bottom sediments, leaves, stems and roots of Typha latifolia L. and Nuphar lutea were collected in August of 2015. The content of metals was determined by flame atomic absorption spectrometry (F-AAS). The results of analyses of sediments and plant material indicate a lack of environmental pollution by nickel (2.58-8.50 mg•kg −1) and lead (3.82-15.99 mg•kg −1) of the Ełk River and its tributaries whereas the cadmium content ranged from 0.16-0.76 mg•kg −1. Nuphar lutea and Typha latifolia L. showed a varied capacity to accumulate nickel (1.20-10.51 mg•kg −1) and lead (0.04-14.16 mg•kg −1), occurring primarily in the roots. The smallest concentration of nickel and lead was recorded in the stems. The highest concentration of cadmium (2.56 mg•kg −1) was noted in the roots and the lowest (0.01 mg•kg) in the leaves. Factor analysis pointed to the processes of mobilizing elements from bottom sediments as a result of pH drop and their uptake by macrophyte roots and sorption processes of metal ions by macrophytes from river waters and their intensive accumulation in bottom sediments.

Water is an excellent solvent, so it can include almost all substances naturally occurring in the earth's crust and substances of anthropogenic origin [Ptoszek 2014, Skorbiłowicz and Ofman 2014]. Among all water bodies, rivers have the most heterogeneous chemical and biological composition, which is often associated with a large area occupied by their catchments [Kiryluk i Skorbiłowicz, 2005]. Over the years, there has been periodically repeated changes in the distribution of mineral component loads in surface waters. The quality of river water in catchment depends from terrain, vegetation, soil type, climatic conditions and anthropogenic pollution [

The aim of the study was to analyze the content of Ni in fractions of 1.0-0.2 mm, 0.2-0.1 mm, 0.1-0.063 mm, 0.063-0.02 mm, and <0.02 mm of river bottom sediments and plants (root, stem, leaf) of broadleaf cattail (Typha latifolia), yellow water lilies (Nuphar lutea), and cowbane (Cicuta virosa). Nickel content in bottom sediment was slightly higher than the geochemical background. The largest amounts of Ni were associated with the finest fraction, while the smallest with the thickest fraction. The highest content of this element was recorded at the point Ełk Barany, which was connected with developing industry in the city of Ełk. All of the tested plants showed greater Ni contents than the amount naturally occurring in plants. In most cases, most of Ni was associated with plant roots, and the least with leaves. It has been proven that aquatic plants can be good indicators of the aquatic environment status.

The inorganic contaminants include metals in the environment. As heavy metals are defined as those whose specific weight exceeds 5 g•cm-3. This group includes, among others, chromium (Cr), cadmium (Cd 2+), nickel (Ni 2+) and lead (Pb 2+) and microelements-zinc (Zn 2+) and copper (Cu 2+). Most of them are highly toxic and dangerousthey accumulate in the environment and causes downturn, mainly in biochemical processes of organic matter decomposition, including a reduction in the efficiency of biological sewage treatment plants and water purifying process [Florczyk and Gołowin 1980, Hermanowicz et al. 1999, Brzóska et al. 2007].