Regulatory guide
NOM-001-SEMARNAT-2021: Wastewater Discharges
Maximum permissible limits for pollutants in discharges to national waters and property
The full table by receiving body, including the karst soil of the peninsula, how often to sample and what changed from the 1996 version.
- NOM:
- Mexico’s official standards
- SEMARNAT:
- Mexico’s environment ministry
- CONAGUA:
- Mexico’s National Water Commission
- EMA:
- Mexico’s laboratory accreditation body
NOM-001 requirements in one minute
| Parameter | Monthly average | Daily average |
|---|---|---|
| Chemical oxygen demand | 60 mg/L | 72 mg/L |
| Total suspended solids (TSS) | 20 mg/L | 24 mg/L |
| Fats, oils and grease | 15 mg/L | 18 mg/L |
| E. coli | 50 MPN/100 mL | 100 MPN/100 mL |
Limits for discharge to karst soil, the case for absorption wells in Quintana Roo and Yucatán. The sea and irrigation have other values (full table below). See the full parameter table ↓
What is NOM-001-SEMARNAT-2021?
NOM-001-SEMARNAT-2021 is the Mexican Official Standard that sets themaximum permissible limits for pollutants in wastewater discharges to national waters and property. It is mandatory for every individual and company that discharges wastewater into receiving bodies owned by the nation.
Important
It replaces NOM-001-SEMARNAT-1996: the limits in its tables 1 and 2 have applied since April 3, 2023, and those for true color and acute toxicity since March 2026. It swaps BOD₅ for COD and fecal coliforms for E. coli.Does your discharge go to the municipal sewer rather than a receiving body? Then this standard does not apply: NOM-002-SEMARNAT-1996, which governs discharges to sewer systems, applies instead. It is still in force and has no 2021 version.
Official text of NOM-001-SEMARNAT-2021
Full text published in the Diario Oficial de la Federación (DOF), the current official reference.
Purpose of the standard
To protect water quality in national receiving bodies by setting limits for basic pollutants, pathogens, metals and cyanides. The limits change with the receiving body:
- Rivers, streams, canals and drains
- Reservoirs, lakes and lagoons
- Mexican marine zones
- Soil: irrigation of landscaped areas, infiltration and other irrigation, and karst soil (the strictest, that of the Yucatán Peninsula)
- Estuaries and wetlands: under the specific discharge conditions set by CONAGUA
Do you manage a hotel?
Your treatment plant is one of six water areas at your hotel
Pools, ice, hot water, mechanical room and drinking water: we cover them in one monthly program, with the compliance file ready for COFEPRIS, the Distintivo H and brand audits.
Table of permissible limits by receiving body
Tables 1 and 2 of NOM-001-SEMARNAT-2021, in mg/L unless another unit is given
Each column depends on where your discharge goes. P.M. is the monthly average, P.D. the daily average and V.I. the instantaneous value (the Spanish abbreviations used in the standard). In all three cases, pH 6 to 9, acute toxicity of 2 TU at most and the true color limits also apply (these two since March 2026).
Karst soilAbsorption and infiltration wells in the Yucatán Peninsula
| Parameter | Monthly avg. (P.M.) | Daily avg. (P.D.) | Instant. (V.I.) |
|---|---|---|---|
| Temperature (°C) | 35 | 35 | 35 |
| Fats, oils and grease | 15 | 18 | 21 |
| Total suspended solids (TSS) | 20 | 24 | 28 |
| Chemical oxygen demand (COD)¹ | 60 | 72 | 84 |
| Total organic carbon (TOC)¹ | 15 | 18 | 21 |
| Total nitrogen | 15 | 25 | 30 |
| Total phosphorus | 5 | 10 | 15 |
| E. coli (MPN/100 mL)² | 50 | 100 | 200 |
| Fecal enterococci (MPN/100 mL)² | 50 | 100 | 200 |
| Arsenic | 0.1 | 0.15 | 0.2 |
| Cadmium | 0.05 | 0.075 | 0.1 |
| Cyanide | 1 | 1.5 | 2 |
| Copper | 4 | 5 | 6 |
| Chromium | 0.5 | 0.75 | 1 |
| Mercury | 0.005 | 0.008 | 0.01 |
| Nickel | 2 | 3 | 4 |
| Lead | 0.2 | 0.3 | 0.4 |
| Zinc | 10 | 15 | 20 |
Mexican marine zonesOcean outfalls
| Parameter | Monthly avg. (P.M.) | Daily avg. (P.D.) | Instant. (V.I.) |
|---|---|---|---|
| Temperature (°C) | 35 | 35 | 35 |
| Fats, oils and grease | 15 | 18 | 21 |
| Total suspended solids (TSS) | 20 | 24 | 28 |
| Chemical oxygen demand (COD)¹ | 85 | 100 | 120 |
| Total organic carbon (TOC)¹ | 21 | 25 | 30 |
| Total nitrogen | 25 | 30 | 35 |
| Total phosphorus | 15 | 18 | 21 |
| E. coli (MPN/100 mL)² | 250 | 500 | 600 |
| Fecal enterococci (MPN/100 mL)² | 250 | 400 | 500 |
| Arsenic | 0.2 | 0.3 | 0.4 |
| Cadmium | 0.2 | 0.3 | 0.4 |
| Cyanide | 2 | 2.5 | 3 |
| Copper | 4 | 5 | 6 |
| Chromium | 1 | 1.25 | 1.5 |
| Mercury | 0.01 | 0.015 | 0.02 |
| Nickel | 2 | 3 | 4 |
| Lead | 0.5 | 0.75 | 1 |
| Zinc | 10 | 15 | 20 |
Soil: irrigation of landscaped areasTreated water for gardens and golf courses
| Parameter | Monthly avg. (P.M.) | Daily avg. (P.D.) | Instant. (V.I.) |
|---|---|---|---|
| Temperature (°C) | 35 | 35 | 35 |
| Fats, oils and grease | 15 | 18 | 21 |
| Total suspended solids (TSS) | 30 | 36 | 42 |
| Chemical oxygen demand (COD)¹ | 60 | 72 | 84 |
| Total organic carbon (TOC)¹ | 15 | 18 | 21 |
| Total nitrogen | NA | NA | NA |
| Total phosphorus | NA | NA | NA |
| E. coli (MPN/100 mL)² | 250 | 500 | 600 |
| Fecal enterococci (MPN/100 mL)² | 250 | 400 | 500 |
| Arsenic | 0.2 | 0.3 | 0.4 |
| Cadmium | 0.05 | 0.075 | 0.1 |
| Cyanide | 2 | 2.5 | 3 |
| Copper | 4 | 5 | 6 |
| Chromium | 0.5 | 0.75 | 1 |
| Mercury | 0.005 | 0.008 | 0.01 |
| Nickel | 2 | 3 | 4 |
| Lead | 0.5 | 0.75 | 1 |
| Zinc | 10 | 15 | 20 |
Does your discharge comply? We take the composite sample at your discharge point and give you the result against the column that applies to you.
Schedule the samplingOther receiving bodies (monthly average)
| Parameter | Rivers, streams, canals and drains | Reservoirs, lakes and lagoons | Soil: infiltration and other irrigation |
|---|---|---|---|
| Temperature (°C) | 35 | 35 | 35 |
| Fats, oils and grease | 15 | 15 | 15 |
| Total suspended solids (TSS) | 60 | 20 | 100 |
| Chemical oxygen demand (COD)¹ | 150 | 100 | 150 |
| Total organic carbon (TOC)¹ | 38 | 25 | 38 |
| Total nitrogen | 25 | 15 | NA |
| Total phosphorus | 15 | 5 | NA |
| E. coli (MPN/100 mL)² | 250 | 250 | 250 |
| Fecal enterococci (MPN/100 mL)² | 250 | 250 | 250 |
| Arsenic | 0.2 | 0.1 | 0.1 |
| Cadmium | 0.2 | 0.1 | 0.1 |
| Cyanide | 1 | 1 | 1 |
| Copper | 4 | 4 | 4 |
| Chromium | 1 | 0.5 | 0.5 |
| Mercury | 0.01 | 0.005 | 0.005 |
| Nickel | 2 | 2 | 2 |
| Lead | 0.2 | 0.2 | 0.2 |
| Zinc | 10 | 10 | 10 |
¹ If chlorides are below 1,000 mg/L, COD is tested; if they are 1,000 mg/L or more, TOC. ² If conductivity is below 3,500 µS/cm, E. coli is tested; if it is 3,500 or more, fecal enterococci. For discharges to soil, helminth eggs: 1 per liter. NA: not applicable.
How often to sample your discharge
Table 4 of the standard: non-municipal discharges, such as hotels and industry
| COD (t/day) | TOC (t/day) | TSS (t/day) | Sampling and testing |
|---|---|---|---|
| More than 3.0 | More than 0.75 | More than 3.0 | Monthly |
| 1.2 to 3.0 | 0.3 to 0.75 | 1.2 to 3.0 | Quarterly |
| Less than 1.2 | Less than 0.3 | Less than 1.2 | Every six months |
The parameter with the highest load governs. The results report is quarterly in every case, and the laboratory files and signs it in the CONAGUA system no later than the seventh business day after the quarter closes.
Penalties for non-compliance
The standard refers to the General Law of Ecological Balance and Environmental Protection (LGEEPA), the National Waters Law and their regulations (section 10.2)
Fine
30 to 50,000 times the UMA, the reference unit for fines (LGEEPA, article 171).
Closure
Temporary or permanent, total or partial, if corrective measures are not met or there is a repeat offense.
Administrative arrest
Up to 36 hours (LGEEPA).
National Waters Law
CONAGUA can impose fines and suspend or revoke the discharge permit.
How to comply with NOM-001
How we work so your discharge complies
Assessment
Full analysis of your current discharges against the permissible limits
Design
Engineering the right treatment system for your operation
Implementation
Installation, start-up and training of your staff
Monitoring
Periodic testing and compliance reports for CONAGUA
Hotels
NOM-001 in hotels in Cancún and the Riviera Maya
Why it matters for hotels in Cancún
The karst geology of the Yucatán Peninsula is unusual. The limestone acts like a sponge that lets contaminants seep straight into the underground aquifer. Unlike regions where clay soil works as a natural barrier, here any inadequate discharge reaches the water table within hours.
Hotels in the Cancún Hotel Zone generate significant volumes of wastewater: a 300-room hotel at 75% average occupancy can produce 300 to 450 m³ of wastewater per day. Without proper treatment, that volume is a direct risk to the ecosystem.
Recommended technologies to comply
To meet the required parameters, the most effective systems in the region include:
Membrane bioreactors (MBR)
They combine the biological activated sludge process with membrane filtration. They produce a high-quality effluent, well suited to reuse for irrigation and toilet flushing, with a compact footprint that helps hotels with limited space.
UV disinfection plus ozone
Combining ultraviolet light and ozone removes pathogens without leaving residual chlorine in the effluent. This matters most when the treated water will reach landscaped areas or be infiltrated into the ground.
Real-time monitoring
Sensor systems can continuously monitor parameters such as pH, turbidity, free chlorine residual and flow. Automatic alerts help prevent non-compliance before it happens.
Action plan for your hotel
- Initial audit: assess the current condition of your treatment plant and your discharge parameters.
- Laboratory testing: run a full profile of the wastewater your operation generates.
- Technical design: work with specialists to size the right system for your volume and type of discharge.
- Implementation: install the selected technology with a controlled start-up plan.
- Ongoing monitoring: set up a program of periodic testing and preventive maintenance.
NOM-001-SEMARNAT: frequently asked questions
Common questions about Mexico’s wastewater discharge standard
Who must comply with NOM-001-SEMARNAT-2021?
Anyone who discharges wastewater into national waters and property: rivers, lakes, lagoons, the sea or soil, including infiltration into the karst soil of the peninsula. It applies to hotels with their own treatment plant, industry, developments and municipalities. If the discharge goes to the municipal sewer, NOM-002-SEMARNAT-1996 applies instead.
Since when has NOM-001-SEMARNAT-2021 been in force?
It was published in the Diario Oficial de la Federación (DOF), Mexico’s official gazette, on March 11, 2022. The limits in its tables 1 and 2 took effect on April 3, 2023, and those for true color and acute toxicity in the fourth year after publication, in March 2026. It cancels NOM-001-SEMARNAT-1996.
How often should I test my discharge?
For non-municipal discharges it depends on the load: with more than 3.0 metric tons per day of COD (or of suspended solids), monthly; from 1.2 to 3.0, quarterly; with less than 1.2, every six months. The report is filed every quarter in the CONAGUA system, no later than the seventh business day after the quarter closes.
What are the monthly average, daily average and instantaneous value?
The daily average (P.D.) comes from a composite of 2 to 6 grab samples taken during the day, according to the hours the process operates. The monthly average (P.M.) is the average of at least two daily averages in the month. You document both through your laboratory results; the instantaneous value (V.I.) is verified by CONAGUA or PROFEPA, Mexico’s environmental enforcement agency.
Why are BOD₅ and fecal coliforms no longer listed?
The 2021 version replaced BOD₅ with COD (or TOC if chlorides reach 1,000 mg/L) and fecal coliforms with E. coli (or fecal enterococci if conductivity reaches 3,500 µS/cm). It also added true color and acute toxicity.
What happens if my discharges exceed the limits?
The standard refers to the General Law of Ecological Balance and Environmental Protection (LGEEPA) and the National Waters Law. The LGEEPA provides for fines of 30 to 50,000 times the UMA (the reference unit Mexico uses to set fines), temporary or permanent closure and administrative arrest of up to 36 hours, plus remediation of the damage.
Can Grupo Eytra help me comply with NOM-001?
Yes. We take the composite sample at your discharge point, arrange the tests in EMA-accredited laboratories, review the operation of your treatment plant and deliver the results ready for the quarterly report to CONAGUA.
Does your hotel’s treatment plant comply with NOM-001?
Effluent testing and a compliance program for hotels and resorts in Cancún and the Riviera Maya