As a result of this study the overload by pollutants and low quality of canal water in the zone downstream of Vrbas and Srbobran towns (Serbia, Yugoslavia) has been recorded. Regarding to started work on demudification of canal bottom in the industrial zone of Vrbas town, in the course of 2000 the additional investigations of mud profile downstrean of wastewater discharge into the canal have been done. In the investigated mud samples the extremely high number of organotrophic bacteria was found (up to 1.7 x 10**10 cfu/ml), but also high number of conditionally pathogenic bacteria (opportunistic bacteria) was recorded. Also, the high number of fecal (thermo-tolerant) coliform bacteria (Escherichia coli and Klebsiella - Enterobacter - Citrobacter group of bacteria), as well as the presence of colifags was found. Such findings indicate possible bad consequences to the health of humans contacting this mud, as well as to the ground water quality, indirectly, via drainage water.

Microbiological examination have been carried within the comprehensive hydrobiological investigation of Grosnica reservoir (Serbia, Yugoslavia) during 1997 and 1998. The aim of investigation was to establish the dynamics and fluctuation of specific physiological group. Grosnica reservoir with its microbial features belongs to quality class 1st-2nd according to Kohl. The comparison of bacteria community varies during the year depending of physicochemical features of a environment and the state of other facts in biocenosis. Dominant bacteria are facultative oligotrophic. The larger number of heterotrophic bacteria is in spring time only. Phosphomineralizers and proteolytic bacteria are present in the large number at the beginning of year, amylolytic bacteria are numerable during the summer and autumn. Number of nitrogen fixing bacteria and aerobic cellulolytic bacteria are changed depending on a season, too.

This paper deals with microbiological and chemical analysis of waste mud, produced in wastewater purification plants of the oil refinery. After digest, mud is removed to the filter press. Compressed mud is placed and stored on the storage yard. Content of organic, anorganic and oil matters and also heavy metals contents were determined. Microbiological analysis comprised determination of total count of aerobic organotrophic organisms and many physiological groups of bacteria. As the indicator of the general biochemical activity, enzymatic (dehydrogenase and phosphatase) activities were determined. Waste mud was mixed with soil (chernozem) in 20%, 40% and 60% amount relations. Changes of activities and quantitative fluctuations of the present microflora were observed after 15 and 30 days. Gained results should enable assessing of using-ability of waste mud in soil-quality improvement, in the sense of its utilization as the fertilizer.

According to microbiological parameters, waters of both small rivers of eastern Backa, Serbia (Yugoslavia), are slightly and moderately polluted by organic matter at the most of the investigated localities in summer season. The satisfactory power of water selfpurification has been preserved in these aquatic ecosystems. In order to prevent further eutrophication processes, certain measures of river water protection and conservation should be undertaken, especially in stagnant parts of investigated waters. Also, the regular monitoring of water quality should be established.

Microbiological monitoring of river water quality is obligatory for use-related aspects such as drinking water production, irrigation and recreation. Assessment of the microbiological quality of water and sediment at the Velika Morava River was performed at five sites, during 2010 and 2011. By applying standard procedures for sanitary correctness and organic load assessment, total of 16 parameters were analyzed. Results of analysis indicated that microbiological water quality of the Velika Morava River is unsatisfactory.

Physico-chemical and microbiological analysis of Brvenica River water was conducted in period 2006-2010 and showed seasonal variations of water quality. The results of correspondence analysis indicated that the year 2006 regarding the physical and chemical characteristics of water, was different from the rest of the examined period. This year was characterized by the absence of ammonia, low contents of nitrite, iron and chlorine, and increased concentrations of KMnO4 consumption. In 2007 and 2008 presence of manganese in water, low concentration of KMnO4 consumption was detected as well increased turbidity and electrical conductivity. And the third distinguish period are years 2009 and 2010 when water was characterized by low concentration of NO3, and the presence of ammonia, NO2, and iron in the water, while turbidity was low and conductivity was average. In Brvenica River water Escherichia coli, Citrobacter sp., Enterococcus sp., Klebsiella sp. are detected. In year 2006 number of aerobic bacteria and total coliforms were rather low, while their number in 2008 is relatively high. Over the whole period, only in 2008 fecal streptococci were not detected. Other years are characterized by growth of aerobic bacteria and total coliforms and the occasional presence of fecal streptococci. Throughout the whole examination period fecal coliform bacteria were present in the water.