Sanitary-Bacteriological Evaluation of Meadow Soils Irrigated with Biologically Treated Sewage
1. S. Niewolak, 2. S. Tucholski, 1. E. Radziejewska
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1. Department of Environmental Microbiology
2. Department of Land Reclamation and Environmental Management
University of Warmia and Mazury in Olsztyn, 10-957 Olsztyn-Kortowo, Poland
Pol. J. Environ. Stud. 2002;11(2):141–149
Studies were carried out to determine numbers of bacteria indicatory of pollution (total number of bacteria on broth-agar at 20 and 37oC) and sanitary state (Total coliforms, fecal coliforms, fecal streptococci and Clostridium perfringens) and of potential pathogens (Aeromonas hydrophila, Staphylococcus sp., Pseudomonas aeruginosa, Salmonella sp.) and fungi on Trichophyton Agar 1 in soils from meadow subject to 8 different variants of irrigation and fertilization in the vicinity of a treatment plant in Olsztynek. Studies were performed in 1996 and 1997. Experimental variants comprised (A) non-irrigated plots (control); (B) irrigated with fresh water; (C) irrigated with biologically-treated sewage (outflow from a waste treatment plant); (D,E, F) irrigated with treated sewage stored in a biological pond with a basic dose, the increased dose up to 150% and 200%; (G) NPK minerally fertilized; (H) NPK minerally fertilized and irrigated with fresh water. Bacteria determined on broth-agar at 20oC were more numerous in the soils of plots irrigated with effluents from a treatment plant and stored in a biological pond. The differences in the number of bacteria determined on broth-agar at 37oC in the soils of different variants were not significant. Fecal coliforms, fecal streptococci (enterococci), Clostridium perfringens, Aeromonas hydrophila and Staphylococcus sp. were generally more numerous in the soils of different irrigated-fertilized variants, less numerous in non-irrigated soils (control). The differences in the number of fecal coliforms in the soils of particular variants were ambiguous. All groups of microorganism were more numerous in the surface layer of the soil. Irrigated dose of treated sewage stored in a biological pond did not influence their number in the soil. Fungi determined on Trichophyton Agar 1 were a constant component of microflora of the examined soils whereas Salmonella sp. was determined sporadically.