Mexican official standard establishes new permissible limits for pollutants in discharges to waters of national jurisdiction

On Friday, March 11, 2022, the Ministry of Environment and Natural Resources published in the Official Gazette of the Federation, the new Mexican Official Standard NOM-001-SEMARNAT-2021, regarding “permissible limits of pollutants in wastewater discharges into receiving water bodies owned by the nation” (“NOM”).

The purpose of this NOM is to guarantee the human rights to water and sanitation, provided in the Political Constitution of the United Mexican States, as well as to establish the regulation of the permissible limits of pollutants in wastewater discharges into receiving bodies property of the Nation. The NOM replaces NOM-001- SEMARNAT-1996.

In this regard, the most relevant changes introduced by the NOM are as follows:

• The Tables of Permissible Limits for wastewater discharges to receiving bodies of national property are modified, establishing stricter limits for Fats and Oils, Total Suspended Solids, Total Nitrogen, and Phosphorus. The above is to encourage users to modify their processes in treatment plants for the use of wastewater in other processes or activities.

• The classification of receiving bodies is modified in order to expressly include more receiving bodies subject to the NOM, as follows:


 • Rivers

 • Reservoirs

 • Coastal Waters

 • Soil (use in irrigation, natural wetlands)

 • Rivers, streams, canals, drains

 • Reservoirs, lakes, lagoons

 • Mexican Marine Zones

 • Soil

This increases the number of water bodies subject to the NOM and therefore creates obligations for water discharges that were not previously expressly regulated in NOM-001-SEMARNAT-1996 (e.g., streams, canals, drains, lakes, etc.).

• Biochemical Oxygen Demand (BOD)1 is replaced by Chemical Oxygen Demand (COD). The above seeks to generate measurements that make it possible to establish whether microorganisms or bacteria are present in the wastewater.

• Inclusion of the Total Organic Carbon (TOC) parameter as an alternative method to measure the organic load of pollutants in waters with high chloride content (with a concentration greater than 1000 mg/l of chlorides).

• The fecal coliform parameter is replaced by the Escherichia Coli and Fecal Enterococci parameters. The above seeks to generate a better measurement of fecal contaminants in wastewater.

• Introduction of the true color and acute toxicity parameters.

• Introduction of new parameters for the permissible limits of total pH, from 5 to 10 (UpH) to 6 to 9 (UpH).

• Establishment of 35 degrees as the maximum temperature for river discharges, reducing the parameter established in NOM-001-SEMARNAT-1996 by five degrees.

• The permissible parameters applicable to metals and cyanides (Table 2 of the NOM) are reduced.

• The frequency for submitting reports and sampling reports is set as quarterly for all cases (municipal and non-municipal discharges), modifying the timeframe established in NOM-001-SEMARNAT-1996 for submitting reports (quarterly and in some cases semiannual or annual).

• The NOM will enter into force on April 4, 2023, with the exception of the following matters:

o The parameters and permissible limits in Tables 1 and 2 of the NOM, as well as the Normative Appendix, will enter into force on April 3, 2023.

o The parameters and permissible limits for true color and acute toxicity will enter into force in April 2026. Until the parameters and permissible limits come into force, wastewater discharges will continue to be subject to NOM-001-SEMARNAT-1996.

In order to comply with this NOM within the established deadlines, the regulated entities of the industrial, agricultural and service sectors that discharge into receiving bodies under national jurisdiction must implement ambitious strategies to diagnose their processes and make adjustments to them in order to be able to comply with the new requirements and parameters established in this NOM. At Von Wobeser y Sierra, we understand the complexity these changes represent and we can help you to analyze the alternatives and legal mechanisms that will allow you to comply in a timely manner with the obligations established in the NOM.

For more information contact our experts:

Edmond Grieger, Partner: +52 (55) 5258-1048 |

Ariel Garfio, Partner: +52 (55) 5258-1048 |

Roberto Flores, Associate: +52 (55) 5258-1048 |

Mariana Plowes, Associate: +52 (55) 5258-1048 |

Elena Gutiérrez, Associate: +52 (55) 5258-1048 |