Investigating the process of endotoxin changes from the drinking water supply source to the water leaving the treatment plant (Case study: Jajrud River)

Background and purpose: The purpose of this study is to investigate endotoxin contamination by separating total endotoxin, free endotoxin, and attached particles from the source of the Jajrud River to the Letian dam and the water inlet of this dam to the treatment plant to the outlet and treated water to identify the source and fate of the types Endotoxin is the identification of the key and critical points of this emerging pollutant along the Jajroud river route, as well as the effect of the implementation of purification processes to reduce the endotoxin produced at each stage and ensure the low level of endotoxin in the outgoing drinking water; to identify and manage the key and critical points of endotoxin activity based on that.
Materials and methods: Sampling in the autumn season of 1401 along the Jajroud River, taking into account the effect of human activities, the entry of sewage into the river, the water depth, and the course of the river from Ab Nik stations, between Ab Nik and Fashm, Fashm, Between Fashm and Lavasan, Lavasan, Letian dam lake, the water outlet after the dam lake and Saeed Abad, as well as the inlet water of Letian dam, to the treatment plant from incoming raw water, chlorinated incoming water, separation water, filters, rapid mixing and Finally, the water was discharged from the treatment plant. Dark glass bottles were used for sampling. The samples were kept cool and immediately transferred to the laboratory. The physical and chemical properties of the sampled water were first measured to measure the activity of endotoxin. Then, the LAL kit (Kinetic-Chromogeni LaL kit, Bioendo ™ KC0828) was used to measure endotoxin by separating total, free, and bound endotoxin.
Results: This research showed that the level of endotoxin activity in Jajrud River water differed in different sampling stations. The amount of total endotoxin varied between 53 and 85 Eu/ml. Free endotoxin and endotoxin bound to particles had different values in other stations. The highest amount of free endotoxin attached to particles was observed in the outlet stations of Letyan Dam Lake and Letyan Dam Lake, respectively. The activity of total endotoxin, free and bound to endotoxin, was also variable during the purification process. The amount of total endotoxin during different processes was observed between 0.6 and 9.4 Eu/ml. The highest activity of free endotoxin was observed in the water of sedimentation filters, while the activity of endotoxin bound to particles in rapid mixing water was higher than in other samples. Also, the chlorination process is a critical process that plays an important role in the amount of endotoxin activity both during the treatment process and in the water leaving the treatment plant. Because during this process, the composition of the microbial community will change, and thus, by reducing or increasing Gram-negative bacteria, it can increase or decrease endotoxin. Also, the amount of free chlorine in purified water is one of the essential things that can affect the amount of endotoxin after leaving the treatment plant. On the other hand, chlorination causes lyses, which can increase free endotoxin bound to particles. According to the results, among the key stations along the Jajrud River are the stations close to the residential areas, which include Fasham and Lavasan because these areas, due to the high level of pollution they have, provide a suitable environment for the microbial community and They create gram-negative bacteria.
Conclusion: It is suggested to carry out more in-depth studies on the difference in microbial communities along the Jajrud River and to determine the relative level of gram-negative bacteria, especially in critical points with more pollution.