The new regulatory framework is based on four pillars:<\/p>\n\n
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- Protection of public health through a preventive approach<\/li>\n\n\n\n
- Universal access to safe and clean drinking water<\/li>\n\n\n\n
- Risk management across the entire water supply chain<\/li>\n\n\n\n
- Greater transparency and access to information for citizens<\/li>\n<\/ol>\n\n
In this context, water disinfection inevitably represents one of the most critical topics, with direct operational implications for operators, administrators, and healthcare facilities that must ensure proper microbiological risk management.<\/p>\n\n
Drinking Water and Microbiological Risk: What the Decree Provides<\/h2>\n\n
Given the potential health implications of microbiological risks associated with water, Legislative Decree 18\/2023 identifies key parameters for determining potability\u2014namely Enterococci<\/em> and Escherichia coli<\/em>, which must be absent.<\/p>\n\n
One of the major innovations introduced by the decree is the inclusion of Legionella<\/em> as a potability parameter, specifically for internal building networks: in other words, the presence of Legionella<\/em> in concentrations exceeding 1000 CFU\/L (this is the threshold set by the decree) renders the water non-potable and prohibits its use.<\/strong><\/p>\n\n
In addition to potability parameters, the decree establishes indicator parameters whose monitoring contributes to the microbiological quality and safety assessment of water. These include Clostridium perfringens<\/em>, coliforms, and colony counts at 22\u00b0C.<\/p>\n\n
Disinfection: Obligations and General Principles<\/h2>\n\n
Article 8<\/strong> of Legislative Decree 18\/2023 stipulates that, if disinfection is applied, it must:<\/p>\n\n
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- Be effective against pathogenic microorganisms;<\/strong><\/li>\n\n\n\n
- Ensure a sufficient and persistent residual disinfectan<\/strong>t;<\/li>\n\n\n\n
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\n \t
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Not result in the significant formation of by-products<\/strong> hazardous to human health or the environment;<\/p> \n<\/li> \n \t
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Be an integral part of a risk-based approach to assessment and management.<\/strong><\/p> \n<\/li> \n<\/ul><\/li>\n<\/ul>\n\n
Moreover, all implemented measures must be documented and traceable for verification<\/strong> by the competent authorities.<\/p>\n\n
When is Water Disinfection Mandatory?<\/h3>\n\n
The decree does not mandate universal disinfection of all drinking water, but acknowledges its importance as a fundamental control measure. Specifically, when disinfection is part of the water treatment or distribution process, its effectiveness<\/strong> must be verified and guaranteed. It is also required that:<\/p>\n\n
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- The concentration of disinfection by-products<\/strong> be kept as low as possible, without compromising treatment effectiveness;<\/strong><\/li>\n\n\n\n
- Chemical reagents use<\/strong>d do not produce residues that would compromise compliance with quality standards;<\/li>\n\n\n\n
- Compliance with parametric values and general obligations defined in Article 4 of the decree is ensured.<\/li>\n<\/ul>\n\n
Furthermore, disinfection is considered appropriate and necessary, within the context of risk assessment and management<\/strong>, when:<\/p>\n\n
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- Documented or potential microbiological risks are present;<\/strong><\/li>\n\n\n\n
The distribution systems are complex or extensively branched;<\/strong><\/p><\/li>\n\n\n\n
- The buildings are considered high-priority<\/strong>, such as hospitals, healthcare facilities, schools, or other sensitive environments;<\/li>\n\n\n\n
- There are conditions favourable to the formation of stagnation zones<\/strong> or extended water residence times in the pipelines.<\/li>\n<\/ul>\n\n
![\"Technician](\"https:\/\/www.monoclorammina.it\/wp-content\/uploads\/2025\/06\/decreto-18-1.jpg\")
<\/figure>\n\nCriteria and Requirements for Disinfection Systems<\/h2>\n\n
The decree does not prescribe a specific solution but imposes compliance requirements based on:<\/p>\n\n
- Chemical reagents use<\/strong>d do not produce residues that would compromise compliance with quality standards;<\/li>\n\n\n\n
- \n
- Ensure a sufficient and persistent residual disinfectan<\/strong>t;<\/li>\n\n\n\n
- Be effective against pathogenic microorganisms;<\/strong><\/li>\n\n\n\n