Approval of Membrane Filtration Systems & Associated Equipment (Advice Sheet 6)

Version 2.5 July 2025

Glossary

1. Introduction

Approval of membrane filtration systems varies from the approval process described in the other Advice Sheets, and so this Advice Sheet relates primarily to membrane filtration systems.

2. Initial Approval

2.1 Application

Applications should be made in the normal way, as described in Advice Sheet 1, and Advice Sheet 12 using the appropriate Application Form.

BS 6920 testing (or European equivalent testing) and full formulation details must be provided for each component that is in contact with water.

Information on the requirements of the Instructions for Use document can be found in Advice Sheet 2. If a preservative is used with the membrane, test data showing the effectiveness of the rinsing procedure (the “die-away curve”) should be included with the application if available. This rinsing procedure should also be described in the IFU.

If a cleaning regime is specified in the IFU, test data showing the effect of the cleaning procedure on the product water (including the concentrations of any cleaning compounds detected in the product water after cleaning) should be included with the application if available.

Reports submitted to the DWI with the application regarding preservative flushing or cleaning procedures must contain:

• A detailed description of how the test was performed, e.g. temperature, free-chlorine concentration, etc.
• Chain of custody of any test samples and test waters
• A summary of the analytical method used
• The detection limits (normally required to be ≤ 10 µg/l), AQC data and accreditation status for the chosen analytical method
• Test results and appropriate graphs

2.2 Testing

Leachates prepared on the complete systems in accordance with BS EN 12873-4 shall be used to:

1. Verify the “die-away curve”, if required.
2. Determine the presence and concentration of parameters requested by the DWI.
3. Verify the effects of cleaning procedures on the product water, if required.

The test rigs needed to prepare leachates can be large. In cases where it is not practical to prepare leachates on the premises of test laboratories care and planning needs to be undertaken to ensure the security of the rigs used for leachate preparation. In these cases the security of the test rig must be fully under the control of the test laboratory, the test rig must be physically isolated from access by any other people and the test laboratory must be present whenever access to the test rig is required. To achieve this degree of security the following in normally required:

• This work is undertaken in a bonded area to which only the test laboratory has access.
• The test laboratory shall take full responsibility for the chain of custody of all test leachates during transport from the test rig to the test laboratory.

The applicant and the test laboratory should submit a draft test protocol, including details of where the leachates will be prepared, what security measures will be put in place (including locks and tamper-proof security seals), and how, and by whom, the test leachates will be transferred to the test laboratory for subsequent analysis. The protocol should include all commissioning, disinfection and rinsing processes, together with information concerning all monitoring and control of test conditions, including the temperature of test water throughout the period of leachate preparation.

If there is any breakdown in security, for whatever reason, this will invalidate the leachate preparation, and the tests will have to be re-started with fresh test units.

3. Changes to Materials or Components

The process for making changes to products is described in Advice Sheet 3. The following is additional information specific to membrane systems.

The following approach taken to changes will depend on the role of the component:

1. small surface area components which were not part of the filtration system, e.g. connectors, valves, etc. Disclosure of the full formulation and conformity with odour and flavour and growth of aquatic microorganisms tests (BS 6920) of the new material or component.
2. components with greater contact with water e.g. pressure vessels, membrane support materials (but not the active coating). Disclosure of the full formulation and full testing to the requirements of BS6920 (Parts 1 and 2) plus TOC and GC-MS analysis of leachates using a static soak to prepare leachates (BS EN 12873-1).
3. active membrane components, full testing to the requirements of BS6920 (Parts 1 and 2) plus TOC and GC-MS analysis of leachates, together with analysis of any specific determinands requested by DWI, using a re-circulating leachate preparation procedure (BS EN 12873-4).