During the 1981-1996 period, qualitative and quantitative structure of oligachaeta communities as indicator of the eutrophication process was investigated in the lake Palic (the 2nd oxidation lake), Serbia (Yugoslavia). The mean annual number of oligochaetes was related to nutrient concentration (total nitrogen and total phosphorus). The analysed data for both oligochaete community and nutrients, leads to the conclusion that the second oxidation lake Palic can be classified as an highly eutrophic environment, with tendency towards dystrophic, particularly in past two years.

In the scope of the Program of surface water quality examinations in the Republic of Srpska (Bosnia and Herzegovina), hydrometric measurements and water quality examinations had been realized, where zooplankton and microzooperiphyton researches have been performed. Sampling were performed in the period from 6th to 20th May 2000, at 13 water courses with taken in total 21 samples. In qualitative structure of examined fauna, Rotatoria, Cladocera and Copepoda groups were treated, with ascertained in total 109 taxa from 41 genus. In qualitative structure periphyton taxa are predominant. On the basis of bioindicatory species structure it is noticed that dominant species are oligasaprobic and oligobetamesosaprobic character.

The work gives the regime of surface water flows with hydrographic net and the regime of waters at hydrologic stations for the period of 1988-1998. Consequently in this paper will be designed a resonant indicator which is derived out of the composite index group of WQI for the flow field in the period under research. Depending on the index points won at the examined profiles, estimation of waterflows quality will be adapted to the goals of indicator users, in this case to the public. Indicators of the type very poor, poor, good, very good and excellent. Hereto it is important to mention that hereby validity of original composite indicator will have to be sacrificed.

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.

The paper deals with evaluation of surface water quality in Vojvodina (Serbia, Yugoslavia) by integral methods. The aim was to emphasize streams and localities where water quality is insatisfied condition longer period of time. The profiles, chosen according to continuity of quality problems which are not results of short excesses, rightfully could be named as a "black points".

Aim of this study was to assess quality of the Danube sediment from the water source "Ratno Ostrvo", which is in the vinicity of the Oil Refinery "Novi Sad" (Serbia, Yugoslavia), after bombardment of the refinery in 1999. In the period March-October 2000, sediment samples were analysed for their oil and oil-derivates contents, i.e. mineral oils contents, by quantitative IR-spectrophotometry, and by qualitative and quantitative GC/MS analyses for their polycyclic aromatic hydrocarbons (PAH) contents. Oil pollution was detected in sediment samples.

The last decade of 20th century in Serbia (Yugoslavia) was marked with economy recession, war surroundings, and finally bombing in the period March-June 1999. Global increment of environmental pollution was one of the catastrophic consequences. War actions caused destroying of big oil refineries and reservoirs, chemical complexes and industrial objects. Afterwards, toxic and carcinogenic substances reached out to atmosphere, soil and hydrographic system. Also, ammunition with depleted uranium was used. Heavy metals are very dangerous, so that, in this paper are presented results of investigation of heavy metals contents in surface soil layers. Heavy metals are movable, by erosion processes, with possibility of reaching hydrographic network and water supply systems. Investigation was carried out at a few localities: Fruska Gora, Ivanovo, Goc and Crni Vrh. Total contents of heavy metals (Zn, Cu, Pb, Cd, Mn) was determined by AAS (atomic spectrophotometry), by usage "Varian-Spectra AA-10" apparatus.

The balance of production and respiration processes in water of Crnojevica river (Montenegro, Yugoslavia) has been estimate, over the estimate correlation between significant parameters of water quality (BOD, % saturation of O2, pH). Correlation between these parameters is established. The balances exist in stationary conditions. But, impact of precipitation is disturbing this state. The hydrodynamic conditions at underground flow and wastewater effluent from the town Cetinje area, has been influence for it, too. The data are referring to small and middle water state.

Concept of anaerobic treatment process of food processing wastewater is discussed. In this scope there are: 1) formulation of anaerobic process, b) general process scheme defining, c) choice of process (digester type, single- and two-step mode, operating temperature), and d) define of process variables (hydraulic and organic load, removal efficiency, quantity and composition of biogas, etc.).