Drinking water is tested for a variety of contaminants to ensure that it meets specific quality standards set by regulatory authorities. The standards are typically based on guidelines established to protect public health. In the United States, the Environmental Protection Agency (EPA) sets the standards for drinking water quality under the Safe Drinking Water Act (SDWA). The standards are divided into two categories: Primary Standards and Secondary Standards.
- Primary Standards: These standards are legally enforceable and are designed to protect public health by limiting the levels of contaminants in drinking water. The primary standards include:
- Microorganisms: Regulations address the presence of coliform bacteria, which can indicate the possible presence of harmful bacteria, viruses, or parasites.
- Disinfection Byproducts (DBPs): These include compounds formed when disinfectants (e.g., chlorine) react with organic and inorganic matter in water. Common DBPs include trihalomethanes and haloacetic acids.
- Inorganic Chemicals: Limits are set for various inorganic contaminants such as arsenic, lead, fluoride, nitrate, and nitrite.
- Organic Chemicals: Standards are established for organic pollutants like benzene, atrazine, and other synthetic organic chemicals.
- Radionuclides: Limits are set for certain radioactive elements like radium, uranium, and gross alpha and beta particles.
- Secondary Standards: These standards are non-enforceable guidelines established to address issues like taste, odor, or aesthetic qualities of drinking water rather than health concerns. Secondary standards include parameters like color, odor, taste, and specific minerals.
- Color: Excessive coloration in water may indicate the presence of organic matter but is not a direct health concern.
- Odor and Taste: Standards are set to ensure that water is aesthetically acceptable for consumption.
- Total Dissolved Solids (TDS): While not directly harmful, high levels of TDS can affect the taste of water.
The testing of drinking water involves regular monitoring of these parameters at water treatment plants, distribution systems, and consumer taps. Water utilities are required to provide annual Consumer Confidence Reports (CCRs) to consumers, detailing the water quality and any violations of water quality standards.
It’s important to note that standards can vary by country, and within the United States, some states may have additional or more stringent standards than those set by the EPA. The World Health Organization (WHO) and other international organizations also provide guidelines for drinking water quality.