Ultra pure water refers to highly purified water that contains almost no impurities. In this type of water, the total number of bacteria required is extremely low, usually measured in CFU/mL (colony forming units per milliliter). Generally speaking, the total number of bacteria in ultrapure water should reach 0 CFU/mL, which means that there should be no bacteria in every milliliter of water. This high standard water quality is usually used in fields that require extremely high water quality, such as laboratory preparation of high-purity reagents or pharmaceutical industry production of drugs.

To ensure that the total number of bacteria in pure water meets the requirements, the following steps are usually taken:

Disinfect water source

Use disinfection methods such as chlorine disinfection, ultraviolet disinfection, etc. to kill bacteria in water and ensure that the water source is clean.

filter

Use appropriate filtration equipment (such as microporous membranes, activated carbon filters, etc.) to filter microorganisms in water, ensuring further purification of water quality.

Monitoring and testing

Regularly monitor water quality, including indicators such as total bacterial count and Escherichia coli, to ensure that the water quality always meets hygiene standards.

Keep the pipeline clean

Regularly clean and disinfect the water pipeline system to prevent bacteria from breeding inside the pipeline.

Regular maintenance of equipment

Maintain the normal operation of disinfection and filtration equipment to ensure their continuous and effective treatment of water quality.

According to the Chinese national standard GB/T6682-2008 "Specifications and test methods for laboratory pure water and ultrapure water", the total bacterial count of ultrapure water is required to be ≤ 100 CFU/mL. This standard applies to pure and ultrapure water used in laboratories, covering applications such as culture medium preparation, laboratory reagent preparation, instrument and equipment cleaning and dilution. However, in actual production and application, the requirements for the total number of bacteria in ultrapure water may vary among different industries and fields. Therefore, in addition to following national standards, it is also necessary to determine applicable standards and guidance based on specific application scenarios and requirements. In the national standard for electronic grade GB/T 11446-2013, the requirement for the total number of bacteria has become more stringent starting from the EW-I level. According to this standard, the total number of bacteria in EW-I grade ultrapure water should not exceed 0.01 CFU/mL

In order to implement the requirements of the national standard GB/T 11446-2013 for monitoring and testing the total bacterial count of electronic grade water EW-I, the traditional method of collecting water samples using sterile bags is no longer sufficient. This is because during the collection process, water samples are easily affected by airborne bacteria, resulting in test results that cannot reach ≤ 0.01 CFU/mL. In order to overcome the influence of the environment during sampling, SGS adopted an online closed filtration method to ensure the purity of the samples.