FAQs How To Guide

Frequently Asked Questions

How To Guide: Applying the CIRIA SuDS Manual (C753) Simple Index Approach to Proprietary/Manufactured Stormwater Treatment Devices

Can alternative sand suppliers be used?

Yes, a list of reviewed suppliers or specifications is as follows:

UK: Hoben Ltd / Minerals Marketing Ltd – HIQ5 Silica Flour.
USA: Sand specification as per NJDEP (2013) NJDEP laboratory protocol to assess TSS removal by a hydrodynamic sedimentation manufactured treatment device.

Can plastic sampling containers be used?

Yes, provided they are laboratory grade sampling containers.

Where can I test in the UK?

Currently the following places have the capability to test in the UK (please contact Hannah Martin if you are aware of other testing houses in the UK with this capability):

Water Research Centre
Chester University (Bench Scale Testing for Metals Capture)
Framatome BHR Limited

What are the criteria that must be satisfied by a person who will complete the independent assessment of the determination of the mitigation indices from the test results?

The person must satisfy the following criteria:

They must be independent from the manufacturer and their business.
They should be qualified to degree level or above in a relevant subject, including mathematics, engineering, physics etc.
They should be familiar with both the relevant test protocol and the British Water ‘How to Guide’ and associated Frequently Asked Questions.
Their employer should comply with a set of published professional standards or they should be a chartered Member of a relevant professional body.
Their professional experience should include having performed tasks such as hydraulic testing, water quality monitoring and taking analytical measurements. They should have demonstrated knowledge and practice of experimental design and setup, sampling methods, handling sample security (i.e., chain of custody), task documentation and data management.
Their relevant experience should consist experience in consulting or academia (i.e., reporting, general laboratory practices).

Sizing Sedimentation Devices

How can the ‘How to Guide’ be applied when filters are only tested at their design flow-rate with the assumption that lower flow-rates will give equal or improved removal rates?

For devices assessed according to “New Jersey Department of Environmental Protection Laboratory Protocol to Assess Total Suspended Solids Removal by a Filtration Manufactured Treatment Device, January 14, 2022” the particle retention efficiency at 100% MTFR will be used for assessments 1 to 4 of the BW CoP to derive the SIA value. This assumes that there is no detrimental effect on particle removal rate below 100% MTFR and the removal rate will be relatively constant across the operating range. The scour test concentration must still be used for assessment 5 of the BW CoP when deriving the SIA value.

Sizing filtration devices

For Section 6.1 of the ‘How to Guide’ on Unit Selection and Scaling, for filter devices that have been tested for total suspended solids (TSS) removal, the devices should be sized in accordance with Section 6 of the New Jersey Department of Environmental Protection Laboratory Protocol to Assess Total Suspended Solids Removal by a Filtration Manufactured Treatment Device January 14, 2022, which dictates how scaling principles must be applied to the depth and composition of the filter media, and the various ratios of the dimensions of the device. The scaling conditions are also suitable for metals and set out and maintain a constant contact time for any sorption processes.

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