SWIG w&wt s&a q&a

More than 60 people attended a recent Sensors for Water Interest Group (SWIG) workshop to review the various UK and European initiatives on standards and accreditation for on-line monitoring in water and waste treatment. There is, reports Michael Scott, secretary and director of the Cambridge-based Group, a clear need for standards at a national level, and it appears difficult to escape the need for European consensus.

Paul Carter, North West Water, kicked off the occasion by explaining why a user such as his company requires standards to control the lifetime costs of on-line instrumentation. His suggestion that each water company generate its own standards sparked an "active discussion", but, with the WIS (Water Industry Specification) 7000 specifications having been unsupported for some years, and in the absence of any other useable widely supported standard, the water companies have little option but to take action of their own.

An early realisation of the BTWG committee was that there had to be some field testing if conformance to the standards was to be demonstrable, and this realisation significantly increased the complexity of the task. Progress has been extremely slow and, despite vocal requests from a few "industry champions", BSi is about to formally request that CEN terminate BTWG 70.3. The interesting question now arises as to which standards body should pick up the work. There is a clear need for standards at a national level and it is hard to escape the need for a European consensus - there was a suggestion that these standards should be at an international level. Users such as Robin Lennox, South West Water, and Laurie Reynolds, Thames Water, voiced support for the writing of standards because they were so important for the setting of their own framework agreements. However, any such standards would have to be application oriented with targets for suppliers to achieve.

Richard Whiteman, Hyder Consulting, described the European Union's ETACS (European Testing and Assessment of Compatibility of on-line Sensors/Analysers) project, the key objectives of which are:

  • The development of a test protocol for validation and comparison of the performance of on-line analysers. The test protocol will be independent of specific sensors/ analysers and specific measurands;
  • Practical testing of the test protocol to assess its applicability in order to produce a final test protocol, revised in accordance with the experience obtained; and
  • Widespread acceptance of the test protocol by producers/suppliers, users and the relevant authorities to assist its early adoption as an agreed European standard.
Good progress is being made but interesting questions have arisen: how is a test house going to recognise that a sensor is not performing correctly, since many instrument responses will be application specific? For example, it might be the first time that the test house has seen the particular sensor or has dealt with a particular application. Some performance characteristics, such as response time, may be affected by fouling, filter blocking or component ageing and this must be taken into account in evaluation and reporting; particularly challenging since the responses may also be application specific.

Evaluations depend on CRMs (Certified Reference Materials) being available while the VAM (Valid Analytical Measurement) project is making good progress, but there was discussion on how to obtain the requisite volumes for every measurand met in the W&WT industry. Several people thought that there existed a need for more concerted action on CRMs.

Instruments to measure ammonia, nitrate and phosphate are being used to develop the protocol and the ETACS team is aware of the importance of the time and cost of testing. Progress has been encouraging but the point was made that the funding is for pre-normative work and the question arises as to who will own the work and carry it forward. Hans Jacobsen, VKI Denmark, introduced ISO/TC 147 WG2, which was formed in Capetown in October 1997, with the following objectives:

  • Define on-line in situ sensors/ analysers and their classes;
  • Define the terminology describing performance characteristics of on-line sensors/analysers;
  • Define the test procedures (lab and field) to be used to evaluate the performance characteristics of on-line sensors/analysers;
  • Define the procedures for qualifications of on-line sensors/analysers in specific applications.
Broad enough scope
ETACS will be used as a starting point since its project proposal stated the content of a test protocol, "which can be the basis for further working the standard organisations". In discussion, Laurie Reynolds, Thames Water, questioned whether the current classes being considered had broad enough scope. The next meeting of the ISO Working Group will be in the Netherlands in May 1999.

There is an urgent need to establish confidence in on-line monitors and John Tipping, Environment Agency, after reviewing the successful development of MCERTS for air monitoring, discussed the EA's objectives in extending MCERTS to cover water monitoring. MCERTS is being developed under EN45011 so as to be compatible with any European scheme. The point was made that the total chain from data source to use is important in establishing confidence, but no independent standard currently exists by which a manufacturer can demonstrate an audit trail. There is a great deal of work to do and the EA is trying to develop a partnership approach. Tipping enquired whether there was a W&WT trade association which might support the estimated 12 to 18 month programme.

It is planned to hold a consultative meeting early in 1999 at which a priority list of measurands might be developed. As always there was extended discussion on how the project was to be funded, but no general conclusions were reached.

Reduced site testing
Dr Huvin Thompson, ABB Instrumentation, was clear that widely accepted independent standards and accreditation procedures should be welcomed by manufacturers because not only did it promote level playing fields, but it should also reduce the proliferation of site testing; often by the same company on different process sites. However, some disquiet was expressed by the smaller companies that the projected costs of between £15,000 and £25,000 per test would be prohibitive when only a small number of low value instruments might be sold.

This SWIG workshop was intended as a forum for review and debate and was not intended to reach firm conclusions, but a lively debate after the presentations produced the following observations:

  • Standards and accreditation should be developed with global objectives;
  • Where will the funding come from and how can the water companies be motivated to work together?
  • Accreditation would increase confidence in the data from on-line analysers and the EA says that its monitoring charges might be reduced, but will the cost of accreditation squeeze out smaller companies?
  • The WIS 7000 series is still a good starting point.
The Environment Agency might be able to fund a co-ordinating group but who would "own" the resulting standards? Various suggestions, such as CIWEM and SWIG, were made but none of them has yet established themselves in such a role.



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