Exposure assessment of nitrate and phenol derivatives in Tehran's water distribution system.

The presence of organic and inorganic contaminants in drinking water is a global concern. Nitrate and phenol derivatives are examples of pollutants that could be of anthropogenic origin. They are associated with numerous health risks, underscoring the importance of monitoring their presence in drinking water. This study aimed to measure nitrate and phenol derivatives, including 2,4-Dichlorophenol (2,4-DCP), Pentachlorophenol (PCP), 2,4,5-Trichlorophenol (2,4,5-TCP), 2-Chlorophenol (2-CP), 4-Chlorophenol (4-CP), and phenol, in Tehran's water distribution system (WDS). The pollutants in Tehran's WDS were significantly and positively correlated with precipitation. The Hazard Quotient (HQ) and the Excess Lifetime Cancer Risk (ELCR) of the detected pollutants were estimated. The results showed that the regional mean of nitrate and PCP in Tehran's WDS were 35.58±8.71mg L-1 and 76.14±16.93 ng L-1 lower than the guideline values of 50 mg L-1 and 1000 ng L-1, respectively. Some districts exhibited nitrate concentration exceeding the allowable limit by a factor of 1.2 to 2.3. Consequently, the nitrate intake in some districts constituted approximately 50% of the reference dose. While PCP as a phenol derivative with more health concerns was identified in Tehran's WDS, the likelihood of its health effects was determined to be negligible.

Effect of dilution factor on the isolation of Helicobacter pylori from municipal wastewater using culture technique.

Background and Objectives: Isolating Helicobacter pylori (H. pylori) from wastewater and culturing it using a conventional method has always been a controversial issue because the bacterium converts into a coccoid form when exposed to an unfavourable environment like wastewater. To clarify the cultivability behaviour of the bacterium in fresh wastewater samples, the effect of municipal wastewater dilation on the cultivation of the bacterium using a conventional method was examined. Materials and Methods: Several dilutions of wastewater samples were inoculated with fresh H. pylori suspension (with McFarland's dilution 0.5) to examine the dilution effect of wastewater on the bacterium isolation. Results: The H. pylori growth was found to be possible for a dilution factor from 1/106 to 1/107 of raw wastewater. In higher dilution factors the growth of fungi was dominant and could prevent the isolation of the bacterium. Conclusion: The optimized technique could be applied in future studies for increasing the chance of H. pylori isolation from fresh wastewater environments.