Guidance

Compliance with BAT-AELs for indirect emissions to water at chemical waste treatment installations: RPS 371

Updated 19 June 2026

Applies to England

This regulatory position statement (RPS) does not change your legal requirement to comply with the conditions of your environmental permit.

However, the Environment Agency will not normally take enforcement action against you if you do not comply with this legal requirement provided that:

• your activity meets the description set out in this RPS
• you comply with the conditions set out in this RPS

In addition your activity must not cause (or be likely to cause) pollution of the environment or harm to human health, and must not:

• cause a risk to water, air, soil, plants or animals
• cause a nuisance through noise or odours
• adversely affect the countryside or places of special interest

1. Activity this RPS applies to

This RPS applies to operators of chemical waste treatment installations. It applies where you are unable to comply with your emission limits to sewer for lead (Pb), zinc (Zn) and hydrocarbon oil index (HOI) in your permit.

This RPS also applies to chemical waste treatment installations and operators of metal shredding waste treatment installations. It applies where you are unable to comply with the Environment Agency’s Monitoring Certification Scheme (MCERTS) when monitoring emissions of HOI and organically bound halogens (AOX) to water.

2. Conditions you must comply with

If you intend to use this RPS, you must notify the Environment Agency by email within 4 weeks of your varied permit being issued, or within 4 weeks of the date of this RPS. Email wastetreatment@environment-agency.gov.uk with RPS 371 in the subject, and include the:

• operator name and permit number
• permit emission limits that you do not meet
• permit emission limits that you do not test and sample in line with MCERTS

2.1 Emission limit values for indirect discharges of Pb, Zn or HOI

You must:

• set out your actions for how you will comply with your permit emission limits to sewer for Pb, Zn and HOI, as applicable, in an improvement plan
• tell the Environment Agency the date by when you will comply with your permit emission limits
• email this to the Environment Agency at wastetreatment@environment-agency.gov.uk
• comply with your trade effluent discharge consent

If you cannot comply with your permit emission limits to sewer, you must not:

• discharge to sewer upon notification by the Environment Agency that your improvement plan is rejected
• discharge to sewer beyond the agreed date for compliance in your improvement plan  

2.2 Analysis for HOI or AOX

You must:

• analyse HOI to EN ISO 9377-2 standards

• analyse AOX to EN ISO 9562 standards

• if your in-house laboratory is not accredited to EN ISO/IEC 17025 or the MCERTS performance standard, send a minimum of 10% of samples as duplicate samples for external analysis at an accredited laboratory 

• ensure monitoring contractors are accredited to EN ISO/IEC 17025 or the MCERTS performance standard

When you report monitoring results for HOI or AOX, as required by your permit, you must:

• include a statement that you have used this RPS
• state which parameters and procedures you have followed

3. Things to note

The Waste Treatment BAT Conclusions were published in 2018. They set BAT associated emission limits (BAT-AELs) for emissions to air and water from chemical waste treatment installations.

Operators must use BAT to prevent pollution of the environment, or where that is not possible, minimise it. The Environment Agency will review permits for chemical waste treatment installations. They will update permits where appropriate to require compliance with emission limit values based on BAT-AELs for indirect discharges to sewer. This will:

• reduce the emissions of Pb and Zn entering the environment

• prevent metals partitioning into sludge at wastewater treatment plants, which can then be spread on land

Chemical waste treatment sites currently discharge effluent to sewer in line with their trade effluent consents. The Environment Agency previously required risk assessments using the H1 methodology for emissions to sewer to determine whether they have a significant impact on the receiving water. However, this did not consider how contaminants such as metals, partition into sewage sludge and are spread on land.

3.1 Compliance scoring for Pb and Zn

You will receive an initial score on your compliance assessment report if:

• your permit is reviewed and varied
• you have breached BAT-AELs for indirect emissions to water for Pb or Zn by more than 100%

The Environment Agency will score your compliance in line with the Waste operations and installations: assessing and scoring environmental permit compliance guidance.

If you meet the conditions of this RPS and agree an improvement plan, the score will be suspended until 1 July 2027 while you implement your improvement plan.

The score will not be suspended if you do not meet the conditions of this RPS or do not agree an improvement plan. Any suspended score will be reinstated if you fail to complete your improvement plan to a satisfactory standard or within the agreed timeframe.

3.2 HOI scoring

HOI can be treated at wastewater treatment works. Under BAT 20, BAT-AELs may not apply if the downstream treatment works abates the pollutants concerned, provided this does not increase pollution in the environment.

Scoring against the BAT-AEL for HOI is suspended while you seek confirmation from your sewerage undertaker of the level of abatement provided. You should reflect this in your improvement plan.

3.3 Laboratory accreditation

There are currently a limited number of UK laboratories with fully accredited monitoring capability for HOI and AOX. The Environment Agency will review this until there is sufficient accredited UK laboratory capacity to meet MCERTS requirements.

You can find accredited organisations on the UKAS website.

4. When you must check back

The Environment Agency will review this RPS by 1 July 2027.

The Environment Agency can withdraw or amend this regulatory position before the review date if they consider it necessary. This includes where the activity that this RPS relates to has not changed.

You will need to check back from time to time, including at and before the review date, to see if this RPS still applies.

This RPS remains in force until it is removed from GOV.UK or is otherwise identified as having been withdrawn.

You can subscribe to email updates about this RPS. These will tell you if the RPS has changed and when it has been withdrawn. Use the ‘Get emails about this page’ feature on the RPS publication page.

5. If you cannot comply with this RPS

If you operate under this RPS but can no longer comply with it, you must:

• stop the activity to which this RPS relates
• tell the Environment Agency immediately by contacting wastetreatment@environment-agency.gov.uk with RPS 371 in the subject

6. Contact the Environment Agency

If you have any questions about this RPS, email wastetreatment@environment-agency.gov.uk with RPS 371 in the subject.