## 3 Results and Discussion
### Microbiological Contaminants  
Heterotrophic bacteria were present in all of the samples examined (Table 6). The samples taken from sites 2 (Ostrov, old Danube branch) and 9 (Siret downstream the confluence with Danube) showed the highest contamination level, with site 2 being classified in Class III--Critical according to the classification set up by ICPDR for bacteriological parameters in bathing water [60]. Heterotrophic bacterial counts in samples taken from sites with codes 3, 4, 5, 8, 10, 12, 15, 19, 22, and 25 show that in these areas the surface waters are also organically contaminated, being classified in the Class II (moderate pollution) of water quality (Table 6) [60]. Heterotrophic bacteria group includes common genus, such as Gram-negatives: _Aeromonas_, _Acinetobacter_, _Alcaligenes_, _Citrobacter_, _Enterobacterium_, _Klebsiella_, _Monaxella Pseudomonas_, and _Proteus_, and Gram-positives: _Bacillus_ and _Micrococcus_[61]. These bacteria are found in a large variety of aquatic environments, including water supplies, wastewater, seawater. Thus, the heterotrophic plate count is used as microbiological indicator of the water quality and the efficiency of water treatment pro cedures [14]. While heterotrophic bacteria are not generally included in risk groups, some of them are reported as opportunistic pathogens, such as _Aeromonas_ spp. (gastroenteritis) and _Pseudomonas_ spp. (skin and lung infections) [62]. Water containing total coliforms may be the result of natural processes rather than fecal contamination. In addition to human discharge fecal pollution, non-fecal sources like local flora and wildlife also contribute to the overall coliform population. In the water environment, coliforms, whether fecal or not, have the potential to not only survive but also to grow if the physical-chemical and biological conditions are favorable. While coliforms by themselves are generally not thought to pose safety risks, their presence in water microbiota suggests that fecal contamination may have taken place, and the presence of the pathogens should be taken into account [63]. In all analyzed samples, total coliforms were detected (Table 6). The sites with the highest levels of contamination were those coded 1,9,8,5, and 11 (Class III--Critical) [60], in which the MPN/100 mL of water was higher than 10\({}^{4}\). The water collected from the site coded 17 presented the most reduced contamination level with total coliforms. Both heterotrophic bacteria and total coliforms showed a negative correlation with pH, as shown by [64]. High concentrations of heterotrophic bacteria in water can lead to organic contamination or the existence of physical, chemical, and biological conditions that facilitate the growth of these bacteria. The concentration of total coliforms is correlated with contamination of waters by feces, and when present in a high concentration, it can increase the risks of pathogens spreading. The amounts and complexity of water pollution with pharmaceuticals have a significant impact on the microbiota, particularly on the microorganisms that pose a risk to human and animal health. In addition, the pathogen bacteria _Salmonella_ spp., _Shigella_ spp., _Yersinia_ spp., _Escherichia coli_, and all members of the coliform group (Enterobacteriaceae family) are important markers of contamination because they are resistant to environmental conditions. Multi-drug resistance and gene transfer pathways are also important indicators of water contamination in relation to pharmaceutical pollutants, type of compounds, and levels of contamination [65; 66; 67]. Biotechnology innovations based on next-generation sequencing (NGS) techniques, such as eDNA metabarcoding, have emerged as a valuable biomonitoring tool for pharmaceutical pollution, providing numerous benefits, including the ability to assess and predict pollution status, identify pollution sources, pollution dynamics, and assess the impact on the diversity and resistance of the microorganisms in water microbiota [68].