NOM-002-SEMARNAT-1996
The NOM-002-SEMARNAT-1996 is an Official Mexican Standard that sets the maximum permissible limits for pollutants in wastewater discharges into urban or municipal sewer systems. Its purpose is to prevent water pollution and protect both public health and sanitation infrastructure.
Who does it apply to?
This standard is mandatory for anyone responsible for wastewater discharge, including those of municipal, industrial, commercial, agricultural, livestock or domestic origin, as well as residential developments and mixed uses.
Main regulated parameters:
The standard sets limit values for various pollutants, with monthly, daily and instantaneous averages. Examples:
| Parameter | Monthly Avg | Daily Avg | Instantaneous |
|---|---|---|---|
| Oils and fats | 50 mg/L | 75 mg/L | 100 mg/L |
| Settleable solids | 5 mL/L | 7.5 mL/L | 10 mL/L |
| Total arsenic | 0.5 mg/L | 0.75 mg/L | 1 mg/L |
| Total mercury | 0.01 mg/L | 0.015 mg/L | 0.02 mg/L |
| Total zinc | 6 mg/L | 9 mg/L | 12 mg/L |
Other requirements:
- pH: between 5.5 and 10
- Max temperature: 40°C
- Floating matter: must be absent
- BOD and TSS: regulated by NOM-001-SEMARNAT-1996
Obligations of the discharger:
- Carry out periodic technical analyses.
- Keep records for at least 3 years.
- Inform authorities about any changes in processes that modify the quality or volume of the wastewater.
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