Abstract
The main purpose of this study was to evaluate the effect of treated sewage flowing from sewage treatment plants located in the basin of the Supraśl river on the concentration and load of metals in river waters and its main tributaries. Three measuringcontrol points were chosen, on the river and its tributaries, located near Grodek, Sokolka and Dobrzyniewo. Selected points were located behind the discharge of treated wastewater from sewage treatment plants respectively – Grodek, Sokolka and Bialystok. The samples of treated sewage and water were collected in a period from May to November, once a month in 2014. Each individual sample was examined for the content of dissolved form of the following metals: Pb2+, Cu2+, Cd2+, Ni2+, Zn2+, Fe2+/3+. After taking into account water flow of the Biala, Sokolda and Supraśl in every month, metals loads expressed in mg·h-1, transported by the Supraśl and its tributaries waters were calculated. In the study monthly metals loads discharged into the Biala, Sokolda and Supraśl by sewage treatment plants in Bialystok, Sokolka and Grodek were also calculated. The studies have shown the impact of metals load in treated wastewater on metals loads in waters of studied rivers based on the obtained correlation. Most of the searched relations between loafs of Pb2+ – r = 0,88; Cd2+ – r = 0,98; Fe2+/3+ – r = 0,45; Ni2+ – r = 0,55; Zn2+ – r = 0,86 were obtained in case of wastewater treatment plant in Grodek and Supraśl waters. In the study period we observed a diversity in concentration of Cd2+, Fe2+/3+, Ni2+ and Zn2+ in treated sewage and in river waters, which affected loads of this metals.
Highlights
The inorganic contaminants include metals in the environment
Much lower concentration of Cd2+ was observed by Palapa and Maramis [2015] in studies on the quality of water in a small stream flowing through Talawaan, which is located in the vicinity of a gold mine in Indonesia
During the studies the concentration difference detected for Cd2+, Fe2+/3+, Ni2+ and Zn2+ in the treated wastewater and the water receivers affect the formation of the loads of these metals
Summary
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 (Cd2+), nickel (Ni2+) and lead (Pb2+) and microelements – zinc (Zn2+) and copper (Cu2+). The most important source is land leaching, containing metals in its composition [Duffy and vanLoon 2008]. They can penetrate waters with their runoffs. The source of increased metal content can be corroded pipelines and tanks, made of raw materials, which was composed from these elements [Hermanowicz et al 1999].
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