In the project Quality of Drinking Water of Banja Luka City, during 2007 the colony of zoobentos around the water factory is followed. The composition of colony is different in both season and horizontal profile. The quality of water in litoral area of river is much worse, because polluted water from ambiental settlement and that is indicated by major number of Tubificidae. During monitoring of the states there was a change of qualitative and quantitative composition of colony, also and the change of individual domination of taxons.

Aquatic biotopes are, due to their features, among the most disposed ecosystems to bioinvasion. Serbia waters are not an exception, with and increasing colonization by allochthnous organisms observed there during the last few decades. Non-indigenous aquatic species were found among plants, vertebrates and invertebrates. The aim of this work is to present the current status of aquatic ecosystems in Serbia in regard to biological invansions and to point up to the problem of introduction, presence and influence of aquatic non-indigenous species.

Biofilm is a complex aggregation of microorganisms, principally bacteria, associated with their extracellular polymers, and surface attached. Many bacteria, mainly saprophytes, but also some oportunistic human pathogens, live in a water sypplying system. Depending on water quality and other factors, these bacteria are able to form biofilms. The formed biofilm is usually resistant to traditional supply system treating methods, including disinfection. The aim of this study is to make a contribution to the knowledge about bacteria Pseudomonas aeroginosa in biofilm structure. By understanding biofilms, wrong interpretation of microbiological results in water supply system samples analyses could be avoided.

Biofilm naturally occurs in many water distributive systems. The aim of the paper is to determine biofilm forming potential of bacteria isolated from tap water from Novi Sad. A colometric crystal violet microtitre plate test was used to determine bacterial potential to form biofilm. The results show that some isolates have a great potential to form biofilm, especially when grow on higher temperature and in the reach nutritive media.

Coagulation and flocculation can be efficiency applied in drinkling water treatment, in order to remove natural organic matter (NOM). However, in the experiments presented in this paper, the water used is very rich in NOM, and required investigations of additional processes. In order to increase the efficiency of coagulation and flocculation processes in removing NOM from groundwater, the following processes were investigated: adsorption on powdered activated carbon (5-30 mg PAC/l) and preozonation with applied ozone doses of 1.1-6.3 mg O3/l. The parameters used to evaluated the changes in NOM content during the experiment were: KMnO4 consumption, UV absorbance at 254 nm, pH and turbidity.

One of the last stages in purification of waste water is by aquaculture pond using macro biological cells - fishes. In such outdoor ponds, oxygen depletion events can occur at anytime, but most likely to cause fish kills during summer hot weather. Aquaculture pond model can predict dissolved oxygen using small number of measurements and very simple numerical model. Alarm system can be activated urgently when the oxygen level drops below a certain concentration, depending on fish species. Such a model is realized for WWTP at Citluk coal mine, close to Sokobanja in Serbia, and explained in this paper.

The length - weight relationship of juvenile anchovy, Engraulis encrasicolus at Bokakotorska Bay (Adriatic sea, Montenegro) was analyzed. The better knowledge of juvenile growth needs more attention for the entire Adriatic, especial for the Montenegrin coast were this investigation made for the first time. The results obtained from this investigation were compared with the data obtained from the period 1989-1991 from the area of Novigrad Sea of the the eastern Adriatic coast (5).

The red algae Womersleyella setacea is Indo-Pacific species but introduced to Mediterranean Sea were is now relatively widely distributed. During research of benthic communities in Ponta Veslo locality (Lusnica peninsula, Montenegrian coast, Adriatic sea) in summer 2007 dense assemblages on rocky substratum and on sea grass Posidonia oceanica (L.) Del. rhizomes were discovered. The impact on biocenosis structure is discussed.