The lack of drinking water in Zajecar was the main reason for building of water barrier on the Grliste river and making the water reservoir. A factory for water processing was also built, but the problems were not disappeared. The conclusion is that the main solution for this ecosystem was in establishing of an monitoring system. That is the reason why we talk out the results of the monitoring and the troubles in this water source as well as in the phases of water processing.

Water quality analyses were performed on littoral water samples, collected on Lake Ohrid in 2002 (January, February, June, July, August and September). Several microbiological parameters were compared. The number of Escherichia coli, the number of organotrophic bacteria and the phosphatase activity index were measured. Samples were collected along the shore of Lake Ohrid, i.e. at the village of Pestani, at Hotel Metropol, in Ohrid Bay and at the lake inflow of River Velgoska. The results of the study show that the different parameters are not compatible in terms of water quality characterization. The differences found are discussed below.

This paper presents the most important results on water quality investigation of the Danube river in the Iron Gate reservoir. The investigations are conducted by the Institute Jaroslav Cerni by means of regular monitoring renewed after a long pause in 2001. The determined phenomena are considered in regard to water quality of the Danube river in the upstream zone.

According to existing national Standard for drinking water quality NO3 sup(-) ion is limited to 50 mg/l. Removal of NO3 sup(-) concentration greater than this limit is necessary. One of the possible methods is biological denitrification with CH3OH. Principals of this method are described in this paper with recommendation for construction of pilot plan on the specific groundwater source.

In order to increased the amount of water in Sjenica water reservoir (because of higher production of electric energy by hydroelectrical power plant), stagnant waters of Pester field were irrigated to Vapa river and Sjenica lake. Former swamp areas and theirs life communities, represented specific biological filter in Pester high, a kind of natural lagoons, where big amounts of polluted water with nutrients were spent a processed (especially salts of P and N) were characteristic for exact area because of intensive cattle production. After the irrigation on Pester field, raw, polluted water with the large amount of nutrients by Vapa river get to the Sjenica water reservoir where they represented main cause of eutrophication and degradation of water quality in this aquatorium. Heterogenic and numerous algal association in canal of the Pester field is nearly leftover of previous specific algological flora which testifies the presence of species Chaetophora incrassata Hazen (new habitat in Serbia), the first class water indicator.

Investigations of phytoplankton were done in the shallow Montenegrin coastal sea during the period from June to December, 2002. These investigations were the continuation from the preceding years. The main intention was to establish the impact of eutrophication to the quantity and composition of phytoplankton i.e. to establish the difference between areas in the bay and outside the bay. Like is previous years, the highest quantities of phytoplankton - microphytoplankton above all, were found in the area of the Boka Kotorska Bay (in Kotor Bay), Montenegro (Serbia&Montenegro). In July, 2.1 x 10**6 cells/cubic dm were found with dominant species Leptocylindrus minimus represented with 1.4 x 10**6 cells/cubic dm. In the area outside the Bay of Boka Kotorska, exposed to the impact of the open sea, values were significantly lower. In front of Budva, maximum was 1.7 x 10**5 cells/cubic dm in July. At locality exposed to the influence of the river Bojana (brackish water), similar values were established, except in October when 1.1 x 10**6 cells/cubic dm were found.

There have been given research results of quantitative and qualitative indices of communal and industrial waste waters of Nis. The research was carried out by the Institute "Jaroslav Cerni" (group of authors) and JKP "Naissus" (4) with the goal of defining as reliable parameters as possible in order to draw up plans for a central wastewater cleansing plant in Nis, as well as several necessary treatments of the industrial waste waters. There have been presented quantities, load and expected load of the total waste water, basic characteristics of urban and natural recipient, waste water influence on the river Nisava and needed degree of cleansing.

According to the plans, the town of Gacko tends to be water supplied from the water reservoir Vrba located at the river Vrba. About 150 to 200 m away is located ash basin. All ash basin area is oriented to the water reservoir and leaking water going directly to the water reservoir. The leaking water has high pH value, alkalinity, high content of sodium, potassium and sulphates. There are some heavy metals, but their concentrations are not significant. The influence of those contaminated water on the lake water quality is only little evident because of the high dilution rate.