Key words: bottled pure water on the drinking machine; Microbial pollution status; Hygienic requirements
In order to understand the microbial contamination of barreled purified water during drinking, improve the quality of drinking water, expand the service scope and standardize the sanitary conditions, we tested the microbial indicators of barreled purified water during domestic drinking in May 2004 according to the national sanitary standards, and now the results are reported as follows.
1 materials and methods
1. 1 sample source: We used the same batch of bottled purified water, distributed it to 20 families and put it on the water dispenser. The inspection began on the same day. First, use 75% alcohol cotton balls to disinfect the two water outlets on the water dispenser, and then aseptically take 500ml of intermediate running water from the cold water outlet and the hot water outlet (boiling) and bring it back to the laboratory for inspection.
1.2 inspection method According to GB 17324- 1998 Hygienic Standard for Bottled Drinking Pure Water, the items of microbial indicators (total number of colonies, coliforms, molds, yeasts and pathogenic bacteria) were inspected, and GB/T4789-94 Microbiological inspection method for food hygiene [
1.3 The experimental medium was prepared according to GB/T4789-94, including common nutrient agar, lactose bile salt fermentation broth, Bengal red medium, S.S agar culture broth and S.C selenite cystine enrichment broth.
The evaluation standard of 1.4 is based on GB 17324- 1998 Hygienic Standard for Bottled Drinking Water. The total number of colonies of qualified products is ≤20cfu/ml, the coliform group is ≤3MPN/ 100ml, and no mold, yeast and pathogenic bacteria can be detected [3].
Two results
See table 1 for the results. We collected 20 domestic bottled drinking pure water (the same batch), and further observed the pollution situation by detecting microbial indicators. The results show that the microbial indexes of the water collected at the hot water outlet (after boiling) are all within the acceptable range. However, all the samples collected at the outlet of the cold water end were qualified. After 3 days, the total number of colonies, molds and yeasts increased, and the increase was obvious with time. During the five tests within 10d, neither coliform nor pathogenic bacteria were detected, which met the national hygienic standard for drinking pure water. According to the national hygienic standard, mold and yeast can not be detected in pure water. The total number of colonies, mold and yeast in this survey exceeded the standard.
Table 1 20 Survey and Inspection Results of Microbial Contamination of Barreled Pure Water in Families (omitted)
After inspection, the results of microbial detection are different, which is statistically significant. The total number of colonies was t=2.273, P < 0.05, and the number of molds was t=3. 135, P.
3 discussion
After inspection, there are three reasons why the microorganisms in bottled pure water on drinking fountains exceed the standard: the total number of colonies, the number of molds and the number of yeasts. First, the plastic bucket of barreled purified water is recycled, and its special structure is not conducive to cleaning and disinfection, resulting in the pollution of the bucket itself. In a suitable environment (light and temperature), a small number of microorganisms will multiply [4]; Second, the interface of the drinking machine is not well sealed, and negative pressure is formed in the bucket when the water comes out, so that various microorganisms in the air are sucked into the water with the air, and the air quality affects the quality of the bottled water, which is easy to be polluted after long-term drinking, and a large number of microorganisms breed; Third, the drinking fountain is exposed in use, and it is inconvenient to disinfect at home, which leads to the microbial index of pure water exceeding the standard. Therefore, we believe that the detection of bottled pure water in domestic drinking fountains in this survey shows that the initial pollution is very light, and all indicators are not beyond the standard. With the extension of time, the total number of colonies increased on the third day and increased obviously on the fifth day. Almost all the pure water has increased, and molds and yeasts have also appeared. It can be seen that the sanitary quality changes of purified water are mainly the total number of colonies, mold and yeast. This is potentially dangerous to human body [2, 3]. It is necessary to strengthen sanitary supervision and monitoring guidance in the production and circulation of barreled drinking water, strengthen training, strictly abide by sanitary standards and operating rules, thoroughly clean plastic barrels in the first process, and regularly disinfect and clean all parts of the drinking machine, advocate drinking pure water from the outlet of boiling hot water instead of cold water, and suggest that plastic barrels filled with pure water should be transformed into barrels filled with water below 10L as far as possible, and the drinking time should be controlled within 5 days, which is light in microbial pollution, hygienic and safe, and beneficial.