## 3 Results and Discussion  
According to the data published in the literature, the process of PCB degradation in anaerobic conditions consists of the separation of chloride ions from congeners [27]. The separated chlorides accumulate in the culture medium. In the conducted research, the amount of chlorides in the culture medium before and after the anaerobic degradation was determined. The theoretical maximum amount of chlorides was calculated on the basis of chromatographic analyses (Table 1). It was 2585.22 ppm. After the biological processes, 193.39 ppm of chloride ions were indicated in the culture medium provided by the sulphate-reducing bacteria (SRB) and 236.07 ppm in the cultures with a presence of denitryfying bacteria (DB). The amount of chlorides that were separated from PCB molecules gave adequately 7.48% for the SRB and 9.13% for the DB of decreasing chloride ions as compared to the initial value. The determination of ion quantity confirmed the course of the dechlorination process. Table 3 shows the effectivnes of the dechlorination process of the chosen congeners in the cultures provided by SRB and DB present in the primary sediments that originated from the petrochemical wastewater sedimentation tank. The results were compared to the chosen PCB congener initial concentrations, which are presented in Table 1.  
In the cultures with the use of SRB and DB microorganisms, the highest degree of PCB degradation was noted for 7-CB, which exceeded 70%. Slightly weaker results were obtained for 6-CB, congener number 153. In all cultures, good degradation effects were observed for 2-CB and 3-CB (over 35%). It is a significant result, as usually the degradation of less-chlorinated congeners focuses on the ring's fissure and the process dominates in aerobic conditions [28]. The separation of chlorides from highly chlorinated PCB congeners, such as 6-CB or 7-CB, has been the best documented mechanism of PCB degradation in anaerobic conditions to date [29; 30]. The determination of the amount of chlorides in the post-culture medium proves the existing hypothesis of the dechlorination process. [PERSON] et al. [31] briefly described the anaerobic PCB degradation pathway, which proceeds by removing chlorines in high-chlorinated molecules from meta positions and then continues to the ortho position of biphenyl rings. The PCB metabolite intermediates activate the expression of enzymes in the reductive dechlorination process. Even if the chloride ions separate from the biphenyl rings they still exist in the environment. The concentration of ions increase, which can cause a negative impact on ecosystems. Fortunately, there are microorganisms which are able to live in the presence of chlorides which stimulate their growth [32; 33]. They provide a chloride moving process to decrease this element in polluted sites. Some strains of halophilic bacteria are able to cope with the osmotic pressure caused by a high concentration of chloride ions in the cytoplasm, and the proteins they produce are stable and active in the presence of high concentrations of these ions [34; 35]. The second process described in this paper focused on the elimination of chloride ions from polluted sites. This process is a consequence of the previous one, which can appear in polluted sites. Figure 1 presents the average concentrations of chloride ions for the control tests and the tests performed after the first, second, and third week of the experiments in two media: (a) aquatic medium with mineral salts and (b) tap water. The effect of the chloride ion concentration changes was observed. The obtained results are presented in Table 4.  
The analysis of the obtained results shows that the decrease of chloride ions in the aquatic environments did not exceed 16%. The results depended on the initial ion concentration and the most significant decrease was observed in the samples with 100 Cl\({}^{-}\) mg/dm\({}^{3}\) after 21 days of cultivation. The results proved that the use of the microorganism mixture was able to move chlorides from environment.