Urban Waste Water Treatment Directive makes new demands on measurement technology

A recent SWIG Workshop attended by almost 70 users, suppliers and regulators, and chaired by Terry Long of the Environment Agency, concluded that there is a great deal of work yet to be done on the design of procedures, standards and instruments before a cost-effective and transparent measurement and audit system is in place to meet the needs of the Urban Waste Water Treatment Directive (UWWTD).

Test-rig for testing the ability of auto-samplers to deal with different abstraction heights.

Test-rig for testing the ability of auto-samplers to deal with different abstraction heights.

In his introduction, Terry Long stated that "self-monitoring is a big difference to what was done before and now the Agency will want to assess the effectiveness of the process generating the discharge. There is a complicated set of rules."

Self-monitoring was chosen based on seven determinands:
  • primary treatment only: BOD and SS
  • secondary treatment: BOD and COD
  • more stringent treatment: BOD, COD, total N, total P (applies to nitrate or eutrophic sensitive zones)
The responsibility is on the discharger but the Agency has a duty to audit self-monitoring to generate confidence, and the whole process must be transparent to ensure high-quality data.

The Agency looks at the total chain of measurement and there are clear advantages, in ease of communication and confidence, if Type Approval and Approved quality procedures are used. The Agency is working hard to ensure that there is a uniformity of approach to all dischargers, and issues proformas and guidelines prior to each audit of a discharger.

Sheila concluded that several issues had already become clear:

  • good communication only comes when key contacts are established;
  • clarity of guidance and policy are essential;
  • work load is high for the Agency and forward planning is essential;
  • partnership with the discharger is key;
  • the right people with the right competence comes only with training;
  • the UWWTD will generate an enormous amount of data so documentation and information handling are vital;
  • learning
Mike Osborne of Metoc reviewed a project conducted in 1996 for the Agency where, in generating E32, four aspects of the self-monitoring requirements were considered:
  • Specification for auto-samplers
  • Reviews of auto-samplers
  • Legal aspects of self-monitoring
  • Strategy for auditing of self-monitoring
Metoc tested auto-samplers at four sites in Wales and concluded that it should draft the specification so that it did not stifle technology. Mike drew attention to the wide discretion the Agency now has which is not detailed in law, including the power of entry to measure; to install and maintain its own measurement; and to obtain records of discharges.

He pointed out that information pursuant to a consent is admissible in law, but that other information is not, and stated that evidence is considered to be accurate unless shown otherwise and failure to provide information carries the same maximum penalty as a discharge offence.

These points raise interesting conundrums. There is no incentive to withhold information, but a discharger may find itself trying to prove that its own information is inadequate in some way. The issue of self incrimination is still to be tested in law.

Certification or accreditation does not affect admissibility of information but could materially add to credibility. But there is not yet an agreed quality control procedure for on-line samplers so it is down to trust between the discharger and the regulator.

Although on-line measurements are not yet accepted as methods for demonstrating consent, they are foreseen in the Directive and the view is that data taken from such monitors, at the intervals specified in the consent, are acceptable.

John Bates of the WRc shared the findings of the group test on auto-samplers carried out by the WRc to the requirements of E32. Unsurprisingly for new products being tested to new requirements there were deficiencies, and most products have been improved as a result.

The most significant problems were in meeting the temperature requirements; many wondered why the temperature range was so high, as 40oC is not often achieved for 24 hours in the UK, and modifying to meet this requirement adds unnecessary costs.

One user wanted to know how the continued performance of the sampler in use was to be checked. No procedure has yet been established but the feeling was that this would be covered by ongoing audit work between the discharger and the regulator.

As an international supplier, Richard Green of Bhler Montec was clear that the supply of auto-samplers is a legislative-driven business. Standards are ambiguous and the requirements vary between member states due to interpretations of ISO5667 and the UWWTD. This is compounded by dischargers working at different rates to achieve compliance. Procurement requirements are rolled up into major tenders and competition is intense.

Richard was concerned that trials so far have been a waste of time as they use different procedures, and there has been little feedback on the results. The tests are being used to determine absolute pass/fail, whereas E32 allows interpretation. He observed that compliance to E32 is voluntary but there is an absolute need to volunteer.

The problem is that E32 does not provide a delivery mechanism for certification and accreditation. The question of what happens to the installed base was raised but no clear answer was available.

Another user questioned the cost of fixed samplers - an estimated £10-15,000 for each site for four samples per year. With hundreds of sites eventually being covered by the Directive, the cost was considered to be excessive. There was a strong plea for the use of portable samplers, not yet covered by E32.

Dr David Westwood of the Agency described the development of MCERTS for stack emissions and outlined the Agency's ideas to extend MCERTS to cover water discharges. Little work has been done so far but the Agency has requested tenders to develop a scheme. The contract is expected to run for up to two years, so MCERTS for water is unlikely to be in place in the very near future. The funding of estimated costs of £20-30,000 for each test was seen as a problem for innovative small companies.

Carole Roberts of North West Water (NWW) described the practical issues of implementing a companywide scheme to meet the Agency's requirements for the UWWTD. A great deal of detailed work is necessary but Carole's most significant problems were in setting up a multidiscipline structure to tackle the logistical problems.

NWW has a large, highly automated, centralised laboratory. The bottle sizes are wrong for the UWWTD needs, and the storage/collection system does not have appropriate timings and routings. This has meant installation of extra fridges on some sites. Considerable effort has gone into training and will continue because of people mobility. Individual manuals containing accredited parts have been set up on each site. Carole does not believe that NWW will use on-line monitors to meet the UWWTD requirements within the next 10 years.

Martin Fenwick, Anglian Water Services, said his laboratory had years of experience meeting the quality standards of regulators such as the DWI, but that it is facing a real challenge in trying to meet the performance requirements of the UWWTD. For example there are no method options for BOD and they could only achieve 7% to 9% uncertainty, whereas the requirement is 5%.

Also the COD approved method is designed for high-level COD and not for low-level COD with high levels of chloride. Martin stated that even the Agency's laboratories cannot meet the uncertainty requirement for total N. He pointed out that the time between sampling and analysis should be ideally less than 24 hours and definitely less than 48 hours, and presents a problem when the sample timing is just before a weekend.

In the final discussion there was a strong feeling that there is a need for standards and accreditation procedures as soon as possible, and concern was expressed at the two years or more before MCERTS for water could be in place. There was a plea that MCERTS for water should encompass E32 since resubmitting instruments for new requirements would be expensive and unfair.

The issue of what would be done with the installed base was left unresolved. Charles Excell, Evaluation International, pleaded for a holistic approach working within a European framework.


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