Izabela Biedroń, Maria Świderska-Bróż, Teodora Traczewska, Agnieszka Trusz-Zdybek, Małgorzata Wolska
Politechnika Wrocławska

The effect of filter media on groundwater quality changes was studied for 6 months. The test system was continuously supplied with groundwater from well, at a constant speed from top to bottom and filter deposits were open to provide contact with air. Filter beds during the study period were not washed. The subject of the study were three beds (Z1, Z2 and Z3) with different filter materials: Z1, Z3 were filled only with an alkaline material, which provided to reduction the corrosivity of water, Z2 – outside alkalising materials also included sand, thus increasing removal efficiency of iron and phosphate ions. Analysis of water physico-chemical parameters include pH, temperature, total alkalinity, intensity of colour, turbidity, dissolved oxygen and the content of: iron, iron (II) and (III), aggressive carbon dioxide, inorganic nitrogen forms (Ninorg), ie NH4 +, NO2-, NO3-, phosphate and total organic carbon. Bacteriological analysis of water samples was based on the total number of psychrophilic bacteria, having an optimum temperature for growth about 22ºC, and mesophilic (37ºC). All analyses were made in accordance with current standards. Groundwater was characterized by high volatility of most of the analyzed indicators of water quality. Due to the low flow velocity of water through the filtration beds and presence of dissolved oxygen in water, there was conditions for microbial growth in the deposits. There were a growth conditions for biofilm development on the surface of filter media. Excess filter media was periodically flushed out by flowing water regardless of the type of material which is contacted with water. Confirmation of the biofilm development on the surface of mineral grains was also indirectly by the increase in the number of bacteria in the filtrate, compared to the number of bacteria in the groundwater. Biological activity of the bacteria on the deposits surface was confirmed by changes in concentration of inorganic forms of nitrogen. All three beds have provided a reduction in inorganic nitrogen, which was assimilated by the microorganisms. Microorganisms on the surface of deposits reduced ammonia nitrogen in the filtrates by nitrification process. In addition, NH4+ particles may be adsorbed on the surface of particulate matter present in the water and retained in the bed. During this research there were no significant differences depending on the type of deposit, in efficiency of removal of inorganic nitrogen.

Słowa kluczowe
materiał filtracyjny; jakość wody podziemnej

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