The most extended and deepest belt of macrophytic vegetation, the belt which almost without exceptions define the lower limit of littoral region of Lake Ohrid, consists algae from the family Characeae. Permanent presence of sunlight, well oxygen saturation, their density which decreases the waves action, together with the facts that these algae are food and shelter for the numerous endemorelic species from the very rich fauna of macro invertebrates, make the stonworts the most attractive life habitat in Lake Ohrid. Our results are found on researching of three types facies from four different localities in Lake Ohrid: sandy-muddy facies without of stoneworts, facies covered by stoneworts and facies covered by Gastropod and Bivalvia shells, also without of stoneworts. Without exceptions, in all four localities we approved the mentioned affirmation about the great importance of the stoneworms as life habitats, both by the number of present taxa and the density of the macro invertebrate communities.

The basic purpose of Gruza accumulation is to supply the town of Kragujevac and its vinicity with drinking water. The accumulation occupies large area, comparing with its relatively shallow water and low water mass, which is essential for water eutrophication. The aim of this research is to determine water quality, through index of phosphatase activity at five locations in one year period. According to the results obtained for index of phosphatase activity, water of Gruza lake belongs to 3rd A category. The maximum obtained value (19.60 micromol/s/cubic dm) was determined in the shallow part, at mouth of the river Gruza in July, 2000, and the minimum one (0.39 micromol/s/cubic dm) in the deepest part of accumulation, at location Brana in March, 2001.

The paper deals with determining the dependence of trihalomethanes forming (chloroform, bromdichlormethane, dibromchlormethane and bromoform) on the contents of natural organic matters from groundwater. The analyses was made bay calculating correlation of trihalomethanes forming potential (THMPF) with UV absorbance and permanganate number as surogates parameters for defining in content NOM in water. These were used to observe the changes in the content of organic matters after coagulation. A good correlation of THMPF, PF chloroform and UV absorbance (254 nm) (coeficient of correlation 0.72 and 0.87) was observed as well as a good with UV absorbance (254 nm) (coeficient of correlation - 0.88) and with PN (coeficient of correlation - 0.80) in coeficient of correlation in bromated trihalomethanes forming.

Every country must to concern the biodiversity of flora and fauna, especially in ecosystems rich with endemic and relict species. Such ecosystem is the Lake Ohrid.

In this paper is given the comparative review of investigation of the macrophytic vegetation and ichthyofauna in 4 localities (Grasnica, Gradiste, Veli Dab, and Cerava) from the littoral region of the Lake Ohrid. In the investigated localities are evidenced macrophytic species and fish species as bioindicators for saprobility. Based on the obtained results, it can be concluded that qualitative composition of macrophitic vegetation and ichthyofauna are different and depend from locatities where investigated made.

The results of a study on the water of the Sumanka river during several years point out the decrease in its quality. The results of the present study show that the technological actions, as well as the some technical changes, carried out in the Lebane's plant in Grgurovci gave the satisfactory effects. Turbidity, colour, KMnO4 demand and ammonia are efficiently reduced, along with low concentrations of Fe, Mn, and residual Al, ensure completely the water standard quality in accordance with the Protocol.

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.

This paper presents a process for phenol removal comprising a reaction step in which phenol is polymerized in the presence of an enzyme horseradish peroxidase. A crude preparation from horseradish roots was used as a low purity source of the enzyme. The technical feasibility of the process was studied using 1 to 10 mM synthetic phenol solutions. Experimental results showed the potential of the proposed technique. A phenol conversion higher than 90% was observed at the polymerization process.

The paper deals with pilot-scale investigations of the effect of preozonation on NOM removal from groundwater by coagulation and flocculation processes. It was found that the preozonation increased the efficiency of organic matter removal by coagulation and flocculation from 23.6 to 47.2% as judged on the basis of KMnO4 values. From the aspect of the change of content of trihalomethanes precursors preozonation exhibits both the positive and negative effects if their content in the water after coagulation is considered in dependence of the applied ozone dose. The obtained values siggest the necessity of careful optimization of the processes of preozonation, coagulation, and flocculation, especially from the aspect of the change in content of the precursors of disinfection byproducts.

Heavy metals contamination of the muscular tussue of nase (Chondrostoma nasus), bream (Alburnus brama) and bleak (Alburnus alburnus) fish species from the Medjuvrsje water reservoir (the Zapadna Mora river), was examined. With the expection of the nase muscular tissue where cadmium (Cd) and mercury (Hg) concentrations above and slightly below MPC, respectively, were detected, the rest of the samples were safe. With the aim of conducting more thorough monitoring of these pollutants, a greater number of elements and a larger number of organisms should be included in the analyses.