The evaluation of microbial indicators of water sources such as rivers, sea and dams is of particular importance because the mentioned microorganisms change the quality of water from a qualitative and health point of view, and on the other hand, they affect the quantitative and qualitative changes of other organisms. The presence of some indicator bacteria such as Escherichia coli, Clostridium, other coliforms, enterococci in water environments indicates low water quality and is a sign of fecal contamination. In this study, the population of indicator bacteria, including heterotrophic bacteria, coliforms and fecal coliforms, psychrotrophic bacteria (Pseudomonas and related genera), isolation of pathogenic and opportunistic bacteria in fish (Streptococcus iniae, Yersinia ruckeri and Aeromonas hydrophila) and human pathogenic bacteria (Shigella dysenteriae, Salmonella typhi and Salmonella typhimurium) in the headwaters Qeshlaq and Gawh Roud rivers of Zhavah dam in Kurdistan province were investigated, and also their relationship with important physicochemical indicators such as temperature, pH, dissolved oxygen (DO), total nitrogen and phosphorus, biochemical oxygen demand (BOD), chemical oxygen demand (COD), turbidity, electrical conductivity (EC), total suspended solids (TSS) and total dissolved solids (TDS) with the aim of evaluating the microbial and health quality of water in selected stations was also determined. The investigated stations include the upstream of Qeshlaq (before the sewage treatment plant in Sanandaj city), the branch of Qeshlaq river (downstream of the sewage treatment plant), the branch of Qeshlaq River (about 3 km below station 2), the branch of Gawh Roud river, the branch of Sirvan (behind the dam) and sampling and quantitative and qualitative analysis of indicator bacteria were tested based on the APHA method. The results showed that the average and standard deviation of heterotrophic bacteria in autumn 2020, winter 2020, spring 2021 and summer 2021 in five stations were 7.30±0.22, 6.54±0.63, 7.08±0.67, 7.58±0.32 CFU/ 100 ml, total coliforms 4.11±1.07, 3.61±1.27, 4.48±0 and 5.23±1.22 CFU/ 100 ml, fecal coliforms 2.84±1.07, 3.042±0.79, 2.86±1.18 and 3.44±1.98 CFU/ 100 ml and psychrotrophic bacteria 5.80±0.46, 5.77±0.49, 5.92±0.44, 6.45±0.16 CFU/ 100 ml respectively. The results of S. typhi, S. typhimurium and Sh. dysenteriae at stations 2 and 3 were positive in all sampling periods. In fact, 8 samples out of 19 examined were positive for human pathogenic bacteria (42.10%). The A. hydrophila was isolated from stations 3 and 4 in the summer season (10.52%). Fish pathogenic bacteria, including Strep. iniae and Y. ruckeri, were not isolated from any of the studied stations.The results of stepwise multiple regression indicated a significant difference between the heterotrophic bacteria with parameters of pH, dissolved oxygen and temperature, and total coliforms with pH, turbidity and temperature (p≤0.05). Also, a significant difference was observed between turbidity and dissolved oxygen with the fecal coliforms (p≤0.05). The increase in other environmental parameters also caused changes in the investigated microbial indicators, but despite this, the resulting changes were not significant. One of the proposed methods to reduce the load of indicator and pathogenic bacteria in the Qeshlaq river is to optimize the sewage treatment process and complete the construction and equipping of the treatment plant in Sanandaj city.
Keywords: Indicator bacteria, Pathogenic bacteria Qeshlaq River, Gawh Roud River, Zhavah dam, Kurdistan Province
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