{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,14]],"date-time":"2026-07-14T12:28:00Z","timestamp":1784032080061,"version":"3.55.0"},"reference-count":54,"publisher":"Public Library of Science (PLoS)","issue":"6","license":[{"start":{"date-parts":[[2025,6,12]],"date-time":"2025-06-12T00:00:00Z","timestamp":1749686400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS One"],"abstract":"<jats:sec id=\"sec019\">\n<jats:title>Background and purpose<\/jats:title>\n<jats:p>Safe and hygienic drinking water is crucial for public health. Secondary bacterial contamination, often caused by improper transport and distribution conditions, poses a significant threat. This study aimed to investigate the physical and chemical factors influencing the microbial status of drinking water in Babol\u2019s distribution network, focusing on the heterotrophic plate count (HPC) index.<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec020\">\n<jats:title>Methods<\/jats:title>\n<jats:p>Thirty-two water samples were collected randomly from Babol\u2019s rural areas and analyzed for HPC, residual free chlorine, turbidity, pH, and temperature. HPC was measured using the plate spreading technique on R2A agar. Descriptive statistics and regression analysis were employed to analyze the data.<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec021\">\n<jats:title>Findings<\/jats:title>\n<jats:p>Heterotrophic bacteria were detected in 61.4% of the samples, with 9.6% exceeding 500 CFU\/ml. The average HPC was 140 CFU\/ml, while residual free chlorine averaged 0.33\u2009mg\/l. In 21.4% of samples, residual chlorine was below 0.2\u2009mg\/l, and 19% had no detectable chlorine. Turbidity ranged from 0.05 to 3 NTU. Statistical analysis revealed significant positive correlations between HPC and pH, MPN, turbidity, and temperature (\u03b1\u2009&lt;\u20090.05).<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec022\">\n<jats:title>Conclusion<\/jats:title>\n<jats:p>Regular HPC monitoring in Babol\u2019s drinking water distribution network is essential to identify contaminated areas and ensure adequate residual free chlorine levels (0.2\u20130.8\u2009mg\/l) for maintaining bacteriological water quality.<\/jats:p>\n<\/jats:sec>","DOI":"10.1371\/journal.pone.0324186","type":"journal-article","created":{"date-parts":[[2025,6,12]],"date-time":"2025-06-12T17:43:51Z","timestamp":1749750231000},"page":"e0324186","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":4,"title":["Investigating the physical and chemical factors affecting the microbial status of water in the water distribution network of Babol City with an emphasis on the HPC index"],"prefix":"10.1371","volume":"20","author":[{"given":"Hossein","family":"Faraji","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hadi","family":"Rahimzadeh","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mehdi","family":"Salari","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zahra","family":"Aghalari","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fatemeh","family":"Asgharzadeh","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6943-4358","authenticated-orcid":true,"given":"Somayyeh","family":"Jafarian","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"340","published-online":{"date-parts":[[2025,6,12]]},"reference":[{"issue":"1","key":"pone.0324186.ref001","doi-asserted-by":"crossref","first-page":"33","DOI":"10.1186\/s12199-019-0790-z","article-title":"Bacterial contamination of drinking water sources in rural villages of Mohale Basin, Lesotho: exposures through neighbourhood sanitation and hygiene practices","volume":"24","author":"P Gwimbi","year":"2019","journal-title":"Environ Health Prev Med"},{"issue":"2","key":"pone.0324186.ref002","doi-asserted-by":"crossref","first-page":"307","DOI":"10.3390\/pathogens4020307","article-title":"Waterborne pathogens: detection methods and challenges","volume":"4","author":"FY Ram\u00edrez-Castillo","year":"2015","journal-title":"Pathogens"},{"key":"pone.0324186.ref003","first-page":"1","author":"World Health Organization","year":"2005"},{"issue":"2","key":"pone.0324186.ref004","doi-asserted-by":"crossref","first-page":"272","DOI":"10.3390\/ijerph16020272","article-title":"Different trends in microbial contamination between two types of microfiltered water dispensers: from risk analysis to consumer health preservation","volume":"16","author":"L Girolamini","year":"2019","journal-title":"Int J Environ Res Public Health"},{"issue":"2","key":"pone.0324186.ref005","doi-asserted-by":"crossref","first-page":"324","DOI":"10.3390\/w15020324","article-title":"An investigation on the effect of leakages on the water quality parameters in distribution networks","volume":"15","author":"D Barros","year":"2023","journal-title":"Water"},{"issue":"12","key":"pone.0324186.ref006","first-page":"1685","article-title":"The interaction between heterotrophic bacteria and coliform, fecal coliform, fecal streptococci bacteria in the water supply networks","volume":"44","author":"N Amanidaz","year":"2015","journal-title":"Iran J Public Health"},{"issue":"16","key":"pone.0324186.ref007","doi-asserted-by":"crossref","first-page":"2964","DOI":"10.3390\/w15162964","article-title":"Are indicator microorganisms predictive of pathogens in water?","volume":"15","author":"L Richiardi","year":"2023","journal-title":"Water"},{"key":"pone.0324186.ref008","doi-asserted-by":"crossref","first-page":"7456410","DOI":"10.1155\/2019\/7456410","article-title":"Sensitivity of heterotrophic bacteria in the low-salinity water areas and estuary in siak district toward pathogenic bacteria in fish","volume":"2019","author":"F Feliatra","year":"2019","journal-title":"Int J Microbiol"},{"key":"pone.0324186.ref009","article-title":"Escherichia, Klebsiella, Enterobacter, Serratia, Citrobacter, and Proteus.","volume-title":"Medical microbiology","author":"MN. 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