Sanitary-Bacteriological Evaluation of Meadow Soils Irrigated with Biologically Treated Sewage

Abstract

Studies were carried out to determine numbers of bacteria indicatory of pollution (total number of bacteria on broth-agar at 20 and 37°C) 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 20°C 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 37°C in the soils of different variants were not significant. Fecal coliforms, fecal streptococci (enterococci), Clostridium perfringens, Aeromonas hydrophila and Staphylococ-cus sp. were generally more numerous in the soils of different irrigated-fertilized variants, less numerous i