Sawdusts of hardwood - oak and black locust, modified with formaldehyde and/or alkali solution, were used as adsorbents zinc ions from model water. The influence of concentration of alkali solution for modification, on zinc ions adsorption efficiency were investigated. Batch adsorption tests were conducted on ambient temperature. Langmuir and Freundlich adsorption isotherm equations were determinated for some adsorbents investigated. Good improvement of adsorption characteristics is achieved by modification of sawdust with alkali. Modification of sawdusts only with formaldehyde results with good prevention of leaching of organic substances as well as poor increase of adsorption efficiency.

The surface water quality preservation is dependent on the used technology of wastewater purification, waters that are thrown in natural streams and on the used methods for the purification efficiency evaluation. The field microbiological test (FMT) is made of a concentrated culture medium that allows the evidencing of enterobacteria below values of 100/cubic cm, therefore it was used for sanitary ranking of treated wastewaters at the sewage treatment plant of Timisoara (Romania). We noted a 100% correlation between FMT and the official coliform bacteria test.

To evaluate precision and reliability of recently introduced Metal Pollution Index as a method for metal pollution monitoring of surface waters, a series of toxicity tests with Daphnia magna have been undertaken. The sampling sites (the River Danube wetlands and Hydrosystem DTD (Danube - Tisza - Danube), Serbia, Yugoslavia) for this study have been chosen according to previously recorded high MPI values. Chemical characterization and WET (whole effluent toxicity) testing of selected waste waters at the chosen sampling sites, and the recipient water toxicity testing upstream and downstream the discharger evaluated the validity of MPI, and, on the other hand, discriminated the effects of background pollution. The results of acute and chronic toxicity tests of water and sediment corresponded well with MPI values, which leads to a conclusion that MPI could be regarded as a reliable and precise method for metal pollution monitoring of surface waters.

This paper is an abstract of the operative program for water protection in the Republic of Serbia (Yugoslavia) for the next five-year period of time. There is a short review on the present water protection status, particularly status of wastewater treatment plants. It includes layouts of water protection solutions in different fields, by priorities, as well as assessment of necessary capital investments for their implementation.

Possibilities of application of transmembrane enzymes as a biological component of a biosensor for water quality control and detection of toxical substances were performed. Synaptic plasma membranes (SPMs) were adsorbed on nitrocellulose filters. The adsorption of SPMs was followed by determination of the transmembrane enzyme Na,K-ATPase. The optimal conditions for SPM adsorption on nitrocellulose filters were determined: 25 microgram per nitrocellulose filter disc during 1 hour of incubation, on - 20 deg C. The ATPase activity of adsorbed SPM showed, that almost 30% of enzymic activity was detected on nitrocellulose filters in mentioned conditions. This results showed that adsorption of SPM on solid support enhancing enzymatic stability and enable its industrial and analytical application.

Withdrawal of water from surface water network should be concerned with preservation of the environment, meaning that the low flow regime in streams should be preserved within the range of natural regime. In order to formulate criteria for minimal allowed flows in streams, it was necessary to perform statistical analysis of low flows in rivers in Serbia (Yugoslavia). The criteria for water withdrawal are proposed on the basis of characteristic ratios between minimum and mean flows. Different criteria are proposed for cold and warm seasons.

Paper points the present water quality of the Moraca river (Montenegro, Yugoslavia), from rivermouth of Zeta to Skadarsko jezero lake. Hydrological analysis, level of water pollution are also presented, together with proposed water quality protection measures regarding the Yugoslav federal regulations for surface waters.

The investigations of the macrozoobenthos of the Crvena Reka river (Serbia, Yugoslavia), left tributary to the Nisava river, were performed during July in 1999. Samples were collected from 15 localities, from the spring of the Crvena Reka river (originating from Toponicka and Vetska rivers) to the lower course, the aim being to investigate the diversity of macrozoobenthos of these running waters which had not been investigated. The community of macroinvertebrates of the Crvena Reka river and the streams, which make it, consists of 54 determined taxa (at species and genus level) from 16 animal groups. Larvae of Ephemeroptera and Trichoptera have the greatest diversity, each having ten determined taxa. The middle course of the Topnicka river (locality T4) is characterized by the greatest diversity (25 taxa), while the springs (due to constant ecological parameters) have poor diversity with two and one determined taxa in locality V1 and V2, respectively. The water quality of the investigated river and streams, which make it, on the basis of the results of saprobiological analysis, is of beta-mezosaprobic quality, i.e. second class of quality in most localities.

This paper points out the role and significance of civil engineering in dealing with the problems related to the water environment. Examples presented consider hydraulic structures and their impact on the aeration level in the watercourse. Aeration and reaeration have the most important effect on the oxygen water quality parameters and therefore on the entire living world in the particular ecosystem.

This paper is an abstract of the operative program for water protection in the Republic of Serbia (Yugoslavia) for the next five-year period of time (2001-2005). There is a short review on the present water protection status, particularly status of wastewater treatment plants. It includes layouts of water protection solutions in different fields, by priorities, as well as assessment of necessary capital investments for their implementation.