Guidance

MCERTS for automatic water sampling equipment

Published 28 March 2025

Applies to England

Introduction

The Environment Agency set up the monitoring certification scheme (MCERTS) to provide guidance on the standards you must meet to monitor emissions that affect the environment. We based the scheme on international standards. It provides for the product certification of instruments, the competency certification of personnel and the accreditation of laboratories. This guidance is for:

• manufacturers of automatic water sampling equipment who need to know what standards to meet to be able to use their equipment for regulatory purposes in England and Wales

• test organisations who carry out testing of the equipment on behalf of manufacturers to see if it meets the required standard

We designed MCERTS to support the measurement requirements specified in environmental permits by making sure that equipment used to derive monitoring data is fit for purpose.

Automatic water sampling equipment

Automatic water sampling equipment (samplers) are used for monitoring treated discharges from wastewater treatment works, industrial processes, untreated wastewater and receiving waters.

Certification body

We have appointed CSA Group Testing UK as the certification body to operate MCERTS on our behalf.

CSA Group Testing UK Ltd complies with EN ISO/IEC 17065 Conformity assessment – Requirements for bodies certifying products, processes, and services.

If you have any questions about the certification process or would like more information on how to make an application, please contact CSA Group Testing UK.

More information about MCERTS is available in the Monitoring emissions to air, land and water collection on GOV.UK.

If you have any general questions about MCERTS, please contact the Environment Agency.

MCERTS certification

Product certification comprises 2 phases. These are:

• laboratory testing – used to determine performance characteristics, where such testing requires a highly controlled environment

• surveillance – initial and continuing which comprises an audit of the manufacturing process to confirm that the manufacturer has provisions to make sure manufacturing reproducibility and to control any design changes to make sure that they do not degrade performance below the MCERTS requirements

The role of the certification body is to assess and certify compliance with the MCERTS requirements for defined applications and conditions. In performing this role, the certification body considers the relevance of the procedures specified in the MCERTS requirements for the product to be certified.

1. Summary

In this section we introduce the scheme.

1.1 Background

1.1.1 This standard is required for the testing of samplers: EN 16479:2023 Water Quality – Performance requirements and conformity test procedures for water monitoring equipment – Automatic sampling devices (samplers) for water and waste water.

1.1.2 The Environment Agency requires operators of regulated processes to use MCERTS certified samplers.

1.1.3 It is the responsibility of the user to make sure that the selection, installation and operation of a sampler is appropriate to the application.

1.1.4 The main performance requirements against which a sampler will be assessed are:

• sample volume bias and repeatability
• maintenance of sample line velocity over the certified conditions including the specified lift height range and when subject to power supply variation
• sample integrity
• timing accuracy
• immunity to ambient temperature variation

1.1.5 The performance requirements and conformity tests apply to samplers that:

• sample aqueous wastewater from non-pressurised (that is open to atmosphere) channels or vessels
• sample over extended periods to collect discrete or composite samples based on time or flow proportional sampling
• are intended to be permanently or temporarily sited

1.1.6 Samplers used at wastewater treatment works final effluent or influent for the purpose of monitoring the performance of the treatment process, as required under the Urban Waste Water Treatment Regulations (UWWTR), shall also be assessed against the requirements specified in EN 16479 (Annex C).

1.1.7 Samplers used for industrial or other applications do not have to be assessed against the requirements listed in EN 16479 (Annex C). However, the certification body shall be consulted on any application specific requirements for which appropriate conformity tests could be determined.

1.2 Performance tests

Performance tests for certification of a sampler against the MCERTS requirements shall meet the requirements of EN 16479 and this document.

2. Scope of the MCERTS scheme

MCERTS for automatic water samplers covers:

• processes falling under the Environmental Permitting Regulations
• consented discharges for processes regulated through provisions of the Water Resources Act,1991
• sites falling under the Urban Wastewater Treatment Regulations (UWWTR)
• sites falling under other relevant directives, for example, the Water Framework Directive
• other monitoring of the aquatic environment

For Environment Agency guidance on samplers used under the UWWTR see section ‘How to take samples’ in Waste water treatment works: treatment monitoring and compliance limits.

3. General requirements

This section describes general requirements for the identification, design and operation of samplers, and information required in manufacturers’ documentation.

General requirements for samplers

The general requirements will be assessed by inspection or the manufacturer’s statement for all samplers.

3.1.1 The manufacturer shall state any specific installation requirements.

3.1.2 A sampler shall meet the general requirements specified in EN 16479 (section 4).

3.1.3 If the certified sampler is based on a previous non-certified model, then the certified sampler shall have a distinct designation to distinguish it from the non- certified model.

4. Performance requirements

This section describes the performance requirements of samplers that need to be tested.

4.1 Performance characteristics

4.1.1 In addition to the general requirements described in section 3, a sampler shall meet the performance requirements specified in EN 16479 (section 5).

4.1.2 Test conditions and procedures specified in sections 5 and 6 shall be used to determine the sampler’s performance.

4.1.3 For samplers not incorporating sample temperature control, if the sampler or sampler variant is only suitable for indoor use, it shall be clearly identified on the sampler.

4.1.4 Samplers that are not certified at a minimum ambient temperature of 0°C or lower shall have a clear label on the sampler, which stipulates the specific ambient temperature range.

5. Provisions for test organisations

For the testing of samplers under MCERTS, test organisations shall demonstrate to the satisfaction of the certification body that their test laboratories comply with the relevant requirements of ISO/IEC 17025 – General requirements for the competence of testing and calibration laboratories.

The results of other tests may be acceptable to the certification body, if they are shown to be equivalent to MCERTS and carried out independently. Manufacturers’ own test data may also be considered, if it also meets the MCERTS requirements for testing and data quality.

6. Laboratory test procedures

This section describes the laboratory test procedures required to assess the performance of the sampler.

6.1 General requirements for testing

Laboratory test procedures shall comply with the requirements of EN 16479 (section 6.1).

6.2 Test Conditions

6.2.1 Test conditions shall comply with the requirements of EN 16479 (section 6.2).

6.2.2 The Environment Agency recommends a set sample volume of 250 ml. Other sample volumes may be used if specified by the manufacturer.

6.3 Verification by inspection

6.3.1 The inspection requirements shall comply with the requirements of EN 16479 (section 6.3).

6.3.2 The manufacturer may set up and demonstrate the sampler before the testing begins.

6.3.3 The test laboratory shall verify and report that the displayed operational status is correct.

6.4 Performance Tests

Performance tests related to sample volume and time are specified below.

6.4.1 Sample volume

The sample volume bias and repeatability shall be determined according to the procedures specified below. All available options shall be tested.

6.4.1.1 Constant time and constant volume (time proportional sampling principle)

Determine the sample volume bias and repeatability in accordance with EN 16479 (section 6.4.1.1).

6.4.1.2 Constant time and variable volume (flow proportional sampling principle)

Determine the sample volume bias and repeatability in accordance with EN 16479 (section 6.4.1.2).

6.4.1.3 Constant time and variable flow (flow proportional sampling principle)

The sample volume bias is tested in 6.4.1.1. The accuracy of the sample triggering system is tested in 6.4.2. Therefore, a separate test is not required.

6.4.2 Testing of sampling principles

The testing of sampling principles shall meet the requirements of EN 16479 (section 6.4.2.1).

6.4.3 Sample line velocity

The sample line velocity testing shall meet the requirements of EN 16479 (section 6.4.3).

6.4.4 Power supply test

The power supply test shall meet the requirements of EN 16479 (section 6.4.4).

6.4.5 Sample integrity

The sample integrity test shall meet the requirements of EN 16479 (section 6.4.5).

The determinands tested for UWWTR are listed in EN 16479 (Annex C). The determinands for industrial applications may be agreed with the certification body.

6.4.6 Sampler timing error

The sampler timing error test shall meet the requirements of EN 16479 (section 6.4.6).

6.4.7 Ambient temperature effects

The ambient temperature tests shall meet the requirements of EN 16479 (section 6.4.7).

6.4.7.1 Test settings

The test settings shall meet the requirements of EN 16479 (section 6.4.7.1).

6.4.7.2 Volumetric test

The volumetric test shall meet the requirements of EN 16479 (section 6.4.7.2).

6.4.7.3 Sample temperature control test

The sample temperature control test shall meet the requirements of EN 16479 (section 6.4.7.3).

7. Certification process

Manufacturers seeking certification should contact the certification body, who will advise on any specific requirements for the automatic sampler under consideration.

7.1 Certification process

A complete sampler shall be a fully functioning sampling system. Only a complete sampler shall be certified. Where a sampler can be supplied with several options, for example mains or battery powered, or where different enclosure options are available, the certification committee shall review how different options may affect performance and decide on the tests that are required for each option.

In selecting the options to be tested, consideration should be given to the options likely to be used in the identified applications. For additional sampler configurations, it may be possible to extend certification by carrying out a subset of the full test programme.

7.2 Certification body and certification committee

The role of the certification body is to assess and certify compliance with the MCERTS requirements for defined applications and conditions.

In performing this role, the certification body shall consider the relevance of the procedures defined in the MCERTS standard to the product to be certified.

Any certification decision shall be taken by an appropriately independent, competent person or group, who are referred to as the certification committee.

On request, the certification body shall provide the Environment Agency with the rationale for any certification decision.

7.3 Certification range

A sampler will be certified over the range for which it is tested. The manufacturer shall state the maximum sampling lift height of the sampler for certification.

7.3.1 Testing

Manufacturers may commission testing from any organisation, provided that the requirements for testing organisations can be met. Manufacturers’ own test data may also be considered but should be assessed to demonstrate that it conforms to the requirements for test laboratories.

The results of previous performance tests may be acceptable to the certification body if they are equivalent to MCERTS requirements and were carried out independently. Any subsequent changes to the sampler shall be demonstrably not significant.

7.3.2 Auditing and surveillance

An audit of the manufacturing process shall be conducted by the certification body to confirm that the manufacturer has provisions to make sure manufacturing reproducibility and to control any design changes that may affect product performance.

Subsequent surveillance audits are normally conducted annually until sufficient evidence of a well-proven, robust system has been collected. Once this has been established the certification body may extend the interval between audits or require submission of specific audit data for review off site.

7.3.3 Certificate validity

MCERTS certificates are valid for 5 years. After this time, the certification is reviewed and any necessary retesting will be identified to maintain the certification. Modifications to the sampler shall be considered as part of this process.

Assessment of re-certification shall be carried out against the MCERTS requirements current at the time of re-certification.

7.4 Modifications to certified automatic sampler

Any spares or replacement parts for certified samplers shall meet the same performance standards as the original parts. Operators and equipment suppliers may be required to provide evidence that the replacement parts meet the required performance standards of the original equipment as specified by the manufacturer of the sampler.

Modifications to certified samplers are allowable so long as manufacturers can demonstrate that these design changes do not degrade the performance of the sampler below the MCERTS requirements.

Manufacturers shall keep detailed records and drawings of all design changes to samplers, and have provisions for design verification, inspection and testing to make sure that the samplers still meet the required performance standards.

The certification body will conduct audits of the design changes to samplers to meet the requirements of product certification. Manufacturers shall notify the certification body of any modifications to equipment that may have a significant effect on the sampler’s performance.

Design modifications or extensions to the range of applications of a sampler may require renewed testing. The extent of this renewed testing will depend upon the nature of the modifications to the sampler.

If there is evidence that a modification has only limited effects on the performance of the sampler, then it would not be necessary to retest a sampler completely. In such cases, only a supplementary test would be required to the applicable MCERTS performance standards.

In the case of modifications to software, detailed documentation (for example, source code) shall be presented to the certification body indicating the nature of the modification as well as resultant effects on operation and functionality. The certification body will then decide if further testing is required.

All samplers submitted for testing shall be a complete sampler system. These specifications do not apply to the individual components of a sampler and a certificate shall be issued for a complete sampler with all its components listed.

8. Example procedure for demonstrating sample integrity for samplers

An example procedure for demonstrating sample integrity for samplers to be used for urban wastewater treatment is provided in EN 16479 (Annex C).

It defines the key performance requirements for automatic sampling equipment, which are intended to be used to collect samples of wastewater treatment works final effluent or influent for the purpose of monitoring the performance of the treatment process. This is applicable to the UWWTR.

The suspended solids test is optional.

Suspended solids are included in the matrix as it is an optional requirement in the Urban Waste Water Treatment Directive (91/271/EEC). The lower range for suspended solids from Table 1 of the Urban Waste Water Treatment Directive (91/271/EEC) has been used in EN 16479 (Annex C). However, the integrity of solids collection is made sure of using the sample line velocity test.

The sampler shall incorporate a means for maintaining the temperature of the samples within pre-set limits of 0°C to +5°C.

9. Evaluation of conformity test data

The evaluation of conformity test data shall comply with the requirements of EN 16479 (Annex A).

10. Format of the report

Test results should be reported in a tabular format as shown in EN 16479 (Annex D). In addition, numerical results from performance tests shall also be presented graphically, where appropriate.