Investigation on Microbiological Indexes in Source Water and Drinking Water of Somewhere in China Northeast

Objective  To investigate the status of microbiological indexes in source water and drinking water of somewhere in the northeast of China and to provide basic information for effectively enhancing the quality of drinking water.

Methods  A total of 92 source water and drinking water samples were collected in the summer and autumn of 2015. Microbiological indexes were analyzed according to the standard examination methods for drinking water-microbiological parameters (GB/T 5750.12-2006), the methods for the examination of natural mineral drinking water(GB/T 8538-2008) and the national food safety standard-food microbiological examination(GB 4789-2013). Three sanitary microbiological indexes, including total bacteria counts, total coliforms and Escherichia coli, and five pathogenic microbiological indicators, including Escherichia coli O157:H7, Salmonella., Shigella and Staphylococcus aureus were detected. If any index in a sample was not qualified according to the provision of the standards for drinking water quality(GB 5749-2006), hygienic specifications for drinking water quality (the Ministry of Health, 2001) and the protocol for developing pathogen TMDLs, first edition (USEPA, 2001), the sample must be judged as disqualification.

Results  The disqualification rate of water samples treated by sterilization, water samples from self-drilled wells and source water were 20.00%, 95.45% and 54.00%, respectively. The contamination of water samples from self-drilled well was more serious. The maximum counts of total coliform and Escherichia coli were 5 600 MPN/100 mL and 344 MPN/100 mL, respectively. The contamination of total coliform and Escherichia coli was the main factor causing high disqualification of drinking water. The correlation among three sanitary microbiological indexes from three water sources was different, which may be related to their living environment. One strain of Salmonella. israel and two strains of Salm. ent. diarizonae were detected in source water, and other three pathogenic bacteria were not detected in all water samples. In addition, there was a statistically significant difference of microbial contamination in water samples between wet season and dry season in this region, while there was no statistically significant difference of microbial contamination between water samples treated by sterilization and water samples from rural self-drilled wells.

Conclusion  Because of the existence of fecal contamination to the source of drinking water in this region, monitoring microbiological indexes of drinking water should be strengthened in this region to prevent the occurrence of waterborne infectious diseases.