Slow sand filtration is an effective water treatment process. However, the performance of slow sand filters is influenced by the raw water turbidity. Filtration on pebble-matrix and roughing filters is introduced as a process effective in reduction of raw water turbidity. Efficiencies of these pretreatments documented on the raw water sources world-wide are presented in this paper as well as the investigation results from the similar raw water source in Serbia (Serbia&Montenegro).

Having known the fact that on the territory of West-Backa region the only water used for water supply system is subterranean water, from different water layers, an assumption can be made that the waters also differ in their physical and chemical content. It is also assumed that these waters differ in their total iron content. The aim of this work is to test the significance of the difference between central water supply systems of West-Backa region (Sombor, Apatin, Kula and Odzaci) for the value of iron in drinking water, using the adequate statistics methods. The central water supply systems in Sombor, Apatin, and Kula are using water from the second water layer (60-75 m), while the water supply system in Odzaci is using deep artesian and subartesian waters (146-220 m). Sombor and Apatin have the raw water purification system and one of the goals is to decrease the concentration of total amount of iron in drinking water.

In this paper, we present the results from both quantitative and qualitative composition of the Gastropod fauna from Lake Ohrid (profile HBZ-Radozda) with their vertical distribution in littoral and sublittoral region of the lake. The results of our investigations shows some changes in biodiversity and the density of gastropod communities that settle this profile, compared with the investigations made 30 years ago.

The area of Zidine is located southwest of Belgrade, Serbia&Montenegro, in the sanitary protection zone of the existing Belgrade water source. This potential water source is capable of yielding water of better quality than that of the existing raw groundwater, for final treatment plants at Bezanija and Banovo Brdo. In view of available capacities of these plants and the raw water system, the water disposal issue is practically resolved and the water source is also highly advantageous in economic terms. Two options of preliminary treatment after settling were considered: sand filters and microfilters.

During the period February 1999 - February 2000 samples of water taken monthly from the area before the outflow of river Crn Drim from the Lake Ohrid, in purpose of qualitative and quantitative investigation of phytoplankton community. During the period of investigation, the phytoplankton community was characterized by forms of Cyanophyta, Bacillariophyta, Chlorophyta, Chrysophyta, Pyrrophyta and Euglenophyta. Qualitative analysis indicated that algae of the division Chlorophyta and Bacillariophyta are dominant in the phytoplankton, while the results of the qualitative analysis showed that forms of Bacillariophyta are dominant. Seasonal dynamics of phytoplankton is characterized by autumnal and winter domination of Bacillariophyta, spring maximum of Chrysophyta and summer domination of Pyrrophyta. The total number of algae varied between 1500-95,700 ind/l in August and February 2000, respectively.

The paper gives the contribute to analyses of the problem of Crnojevica river (Montenegro, Serbia&Montenegro) water pollution. The analyze surround measurement the next parameters: pH, conductivity, oxygen balance, sanitary parameters, content of different form of phosphorus. These measurements are carried out over five sampling series, at the seven stations, including underground flow rate in the Obod cave. Our estimations are confirmed the continuity of the Crnojevica river pollution, by municipality and strain water from Cetinje urban area. Nutrients, especially phosphates, from the pollution emission, attend conditions (together with many natural factors) for production biomass quantity. The opposite processes, the inhibition processes, exist. Phosphorus in the water attends increase level of the water pollution (over increase eutrophication degree), so the water is out of the legal class, because its usage is limited.

As a consequence of bombing of Novi Sad Oil Refinery, Serbia (Serbia&Montenegro), the spillage of large amounts of oil and derivatives caused hydrocarbons pollution of the area surrounding the Refinery and the river Danube, thus directly endangering the entire water source "Ratno ostro". As a measure of protection in the division zone of the Refinery and the water source area, a hydraulic barrier was constructed. Within the process of monitoring piezometer water quality and the water supplied by protection system wells, microbiological analyses of water were carried out with the aim of supervising the barrier functioning. The results have shown that bacterial populations in polluted areas exhibit a duel role: they act as bioindicators of a certain pollution, but at the same time they take part in the process of selfpurification.

The paper presents results of research on hydrophilic flora of the Grosnica reservoir in the Kragujevac basin (Serbia, Serbia&Montenegro). The obtained results confirm that the development of hydrophilic vegetation is dependent on the time, manner, and place of reservoir formation, as well as on the extent of human influence. Analysis of floristic composition of hydrophilic plants of this reservoir indicates presence of 30 species belonging to 20 families. Floristic composition of the hydrophilic flora with flora elements, life forms and ecological factors are presents.

Water reservoir "Gruza" is used forthe water supply of the town of Kragujevac and it's surroundings. The paper shows a comparative overview of physical, chemical and microbiological parameters during the period of 1987-1989, and 1997-1998. Variations of physical, chemical and microbiological parameters are given in the paper.

In this paper are presented the investigation of macrophytic vegetation along Macedonian shore of Lake Ohrid (Radozda-Sv.Naum). The meterial were collected from 59 localities. The results of investigations show that in investigated localities were evidenced 25 different plant species. The number of macrophytic species in different localities vary from 2 to 18 macrophytic species. The differences in the number of macrophyte species are most due to the different ecological conditions in the investigated localities: temperature, light regime, type of soil, configuration of the lake bottom, water level, nutrient amount etc.