Overview
SIST EN ISO 6222:1999 specifies a standardized method for the enumeration of culturable micro-organisms in water, using colony count after aerobic incubation in a nutrient agar culture medium at 36 °C and 22 °C. This European Standard is a critical tool for assessing water quality, particularly the operational efficiency of water treatment processes and the safety of water intended for human consumption. The method is broadly applicable to all types of water, including public drinking water, bottled water, and natural mineral waters.
By employing a culture-based approach, the standard enables laboratories and water suppliers to detect and quantify aerobic micro-organisms, serving as an essential component of routine water quality monitoring and hygiene assurance.
Key Topics
- Enumeration of Micro-organisms: A well-defined protocol for counting culturable bacteria, yeasts, and moulds in water samples by inoculation and growth on nutrient agar.
- Incubation Temperature Range: Analysis is performed at two temperatures: 36 °C to identify organisms suited to human body temperature, and 22 °C, which is optimal for environmental micro-organisms.
- Sample Handling: Recommendations for water sample collection, preservation, and timely analysis to minimize contamination and changes in micro-organism counts.
- Reporting: Results are expressed as colony-forming units per millilitre (cfu/ml), providing a quantitative measure of microbiological water quality.
- Laboratory Practices: Guidance on media preparation, dilution protocols, and counting techniques to ensure reproducibility and reliability.
Applications
SIST EN ISO 6222:1999 is widely used in the following sectors:
- Public Drinking Water Monitoring: Routine examination of municipal water supplies to verify the effectiveness of treatment processes such as filtration and disinfection, and to assess the integrity of distribution systems.
- Bottled and Mineral Water Quality Control: Ensuring compliance with microbiological standards for water intended for human consumption, including water in closed containers and natural mineral waters.
- Industrial and Environmental Hygiene: Checking water purity in food and beverage production to prevent contamination, as well as monitoring surface and groundwater as part of environmental protection programs.
- Early Warning and Incident Investigation: Identifying abnormal increases in micro-organism levels which may indicate contamination or failure in water treatment systems, prompting further investigation and corrective action.
The method is particularly valuable due to its simplicity, versatility, and established reliability in detecting sudden changes in bacterial counts that can signal potential pollution or hygiene lapses.
Related Standards
Organisations implementing SIST EN ISO 6222:1999 may also refer to the following key standards for complementary guidance on water microbiology and laboratory analysis:
- EN ISO 3696: Water for analytical laboratory use - Specification and test methods
- EN ISO 5667-3: Water quality - Sampling - Guidance on the preservation and handling of samples
- EN 25667-2: Water quality - Sampling - Guidance on sampling techniques
- ISO 6887: Microbiology - General guidance for the preparation of dilutions for microbiological examinations
- ISO 8199: Water quality - General guide to the enumeration of micro-organisms by culture
These standards support the correct application, validation, and reporting of microbiological analyses and help laboratories maintain compliance with international best practices for water quality assessment.
SIST EN ISO 6222:1999 thus forms a fundamental part of comprehensive water safety and monitoring programs, supporting public health and regulatory compliance through robust and reproducible microbiological testing.
