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.

In this study possibilities for application of natural aluminosilicates, zeolites in the wastewater treatement has been investigated. Under the laboratory conditions the pilot experimental a column filled with aluminosilicates was established. Technological characteristics of the system were estimated by wastewater flow monitoring and calculation of Darcy filtration coefficient.

Samples for phytoplankton investigations were collected in annual period (September 2003 - August 2004) in the Kotor and Risan Bay. Mean-values percentage contribution of the group diatoms (Bacillariophyceae) through the annnual period were from 79.70% to 86.50%. Species Skeletonema costatum, Pseudo-mitzschia delicatissima, Leptocylindrus minimus and Chaetoceros affinis, were the main edificators of diatom population. Densities of these species were from 10**5 to 10**6 cells/cubic dm. These values are characteristic of eutrophic and extreme eutrophic area. It is needed one permanent monitoring to protect this part of Boka Kotorska Bay negative consequences.

Growing number of population require growing demand for water. In Sremska Mitrovica area geohydrology conditions of neogen sequence have properties of good collector for groundwater. Geological factors are such that atresian groundwater in Sremska Mitrovica area are divided in four hydrogeological zones. In all zones physical and chemical characteristics of groundwater comply with conditions for water supply.

The results of researches of the degree of metals (Fe and Cu) of accumulation in certain species aquatic macrophytes and their organs which sampled in three lakes near city Kragujevac are exposed in this study. The results show variability of the degree of accumation of Fe and Cu among species, their organs and researched localities, and capacity of some aquatic macrophytes species and their organs which accumulate high level of mentioned metals from aquatic environment. Results obtained in this reserches pointed important role of macrophytes vegetation in bioindication and phytoremediation, and ability for use for monitoring pollutants, in studies of quality aquatic ecosystems and their protection, repairing and revitalization.

During 2005-2006 the seasonal researches were taken place aiming to investigate the influence of the urban waste water on the qualitative and quantitative structure of the community of macrozoobenthos in Gabrovacka river. For this purpose five sites were determined and the sampling of the macrozoobenthos was organized on the seasonal level using Surber net.