The microbiological quality of the groundwater was monitored by determining relevant physiological groups of bacteria (organotrophic bacteria) which are indicators of water organic pollution. Standard high nutritive medium (Nutrient Agar) and low nutritive medium (R2A agar) were used. The enzymatic activity was also estimated based on IFA determination (index of phosphatase activity). According to the number of organotrophic bacteria and categorization by Kohl (Kohl, 1975) water is generally classified in category II. IFA showed variation of water quality, which varied from polluted to very pollute. The results showed organic pollution of groundwater and confirmed the sensitivity of enzymatic methods. In addition, cultivation methods confirmed superiority of low nutritive media.

The paper presents the results of laboratory research and application of continuous electro-coagulation and electro-flotation (ECEF) to remove natural organic matter (NOM) from groundwater in the treatment of drinking water. The highest NOM removal efficiency for current density of 5.78 mA/ cm square according to UV254 absorbance and dissolved organic matter (DOC) was 77% and 71% respectively. The specific energy and aluminum electrode consumption was 2.01 kWh/cubic m, 80 g Al/cubic m, respectively.

In the 21 century drinking water of acceptable quality should be available to every person. Numerous investigations are on-going worldwide around the world, to develop innovative and cost attractive approaches for production of high quality drinking water. To allow application of new treatment technology in practice, pilot testing under field conditions are required. Groundwater used for drinking water productions in the Subotica municipalities (Serbia) contains elevated concentrations of arsenic, iron and ammonia, and therefore provided a good basis for continuation of research of UNESCO-IHE, the Netherlands Institute for Water Education, that has been developing innovative water treatment technologies specifically in the field of groundwater treatment and specifically arsenic removal. Objective of this project presented in this paper were to test under field conditions IHE ADART, the innovative adsorptive arsenic removal technology. The pilot project has demonstrated that in addition to conventional approach based on coagulation and break-point chlorination, there is and alternative treatment approach based on biological ammonia removal and adsorptive removal of arsenic that could be economically and ecologically attractive.

Parallel with the ground water physico-chemical quality examinations and the other long term exploring works on the infiltration wells of the Belgrade (Sava alluvium) and Trnovče (Velika Morava alluvium) groundwater sources the microbiological, chemical and crystallographic analysis for the ocher from horizontal drains walls, pumps and discharge pipelines were carried out. One of the objectives of this paper is showing the importance of eco-physiologic groups of bacterium which initiate the aging well processes with their life activities. In ocher, bright field microscopy and SEM analysis determined the presence of genera and species of iron-manganese oxidizing bacteria. Mineralogical – crystallographic content were determined using SEM –EDS, X –ray fluorescence and XRD-methods.