Drinking Water Quality Standards: Microbiological, Chemical, and Radioactive Parameters
Drinking Water Quality Standards
Type I: Microbiological Parameters and Turbidity
Criteria for microbiological parameters and turbidity:
- Microbiological Contamination Indicator Microorganisms: Microorganisms from the coliform group are a good indicator of microbial water quality. Water must meet the following characteristics:
- For all samples analyzed monthly, a drinking water service accepts the presence of total coliform in:
- One sample when fewer than 10 samples are analyzed in the month.
- 10% of the samples when 10 or more samples are analyzed in the month.
- Of the samples analyzed monthly, the accepted presence of coliform is greater than or equal to 5 UFC or NMP.
- All samples analyzed monthly on a water service must be free of Escherichia coli.
- For all samples analyzed monthly, a drinking water service accepts the presence of total coliform in:
- Turbidity: In drinking water, each service must meet the following requirements:
- The average monthly turbidity must be less than or equal to 2 UNT.
- Of all samples analyzed monthly, samples between 10 and 20 NTU may not correspond to the same 24-hour period.
Type II: Criteria for Elements or Chemicals of Health Significance
Drinking water should not contain elements or chemical substances in concentrations greater than the established limits. For example, Copper (Cu) 2.0, Iron (Fe) 0.3, Magnesium (Mg) 125.0 (essential elements). Some non-essential elements, such as Arsenic (As), should not exceed 0.01, and nitrite should not exceed 3. Organic substances like toluene should not exceed 700. Pesticides like Lindane should not exceed 2.
Type III: Criteria for Radioactive Elements
Drinking water should not contain radioactive substances in concentrations greater than: Strontium 90, 0.37 Bq/L.
Type IV: Parameters Related to Organoleptic Properties
Drinking water must meet certain requirements, such as organoleptic parameters (phenolic compounds), with a ceiling of 2.
Type V: Parameters of Disinfection
Distributed drinking water must be submitted to a disinfection process, and there should be a residual concentration of active disinfectant in the network permanently. The maximum concentration of free chlorine residual should be 2.0 mg/L under normal conditions. The minimum concentration of free residual chlorine should be 0.2 mg/L. The use of any disinfectant other than a chlorine generator must be authorized by the competent authority, which sets the minimum and maximum concentrations, tolerance, controls, and methods of determination of residual disinfectant in the network.
Definitions
- Competent Authority: The one designated by the laws and regulations to this effect.
- Drinking Water: Water that meets all the requirements described above (types) that ensure its safety and suitability for human consumption.
- Total Coliform: A group of aerobic and facultative anaerobic bacteria.
- True Color: Color caused by dissolved substances in water, like iron, manganese, lignans, and industrial discharges.
- Pollution: Presence of elements, compounds, or organisms that modify the physical, chemical, and biological properties of water, exceeding the established limits.
- Escherichia coli: Coliform bacteria that, at an adequate temperature, ferment lactose, producing acid and gas.
- Critical Parameters: Parameters characteristic of the source of service.
- Radioactivity: The spontaneous disintegration of atomic nuclei of certain elements.
- Taste: Taste sensation produced by substances in the water.
- Turbidity: Optical interference of the materials by suspending them in water, which causes a reduction of its transparency.