WAC testing (Waste Acceptance Criteria)

WAC testing refers to the Environment Agencies Waste Acceptance Criteria for disposal of waste to landfill. 2005 saw changes in the Hazardous Waste and Landfill Regulations resulting in stricter controls being applied to waste disposal. The purpose of the testing is to investigation the potential hazard in a ‘worst case scenario’ and is accepted as being more relevant than considering ‘total’ content particularly in the context of assessing environmental risk and in particular to aqueous environment.

In effect WAC is a pass or fail compliance test against regulatory limits, categorising waste into 3 waste streams:

      Hazardous (formerly “special waste”)                                                Non – Hazardous                                                           Inert

Wastes can only be accepted at a landfill if they meet the relevant Waste Acceptance Criteria (WAC) for that type of landfill

There are two distinct suites of WAC testing, with the parameters and associated limits dependent upon both the class of waste and the type of landfill for which the waste is destined. The two classes are;

1) An Inert waste landfill suite and 2) a procedure to differentiate between Stable non-reactive hazardous waste in non-hazardous landfill and Hazardous waste landfill

Despite the differences between the classes, they all require the waste to undergo a two part leaching procedure for calculation of the cumulative release of a number of inorganic parameters. (this may change to a single stage leaching process in the future) The test involves applying a leaching test to a representative sample of waste and subjecting it to leaching in water under specific test conditions. Further testing can also be required e.g.; Acid Neutralisation Capacity (ANC) to asses the materials stability under varying pH conditions

 

For more information see the following links

EA - Use of higher landfill waste acceptance criteria limit values

EU -  Landfill of waste

DEFRA- Environmental Permitting Guidance; The Landfill Directive -PDF

MCerts

MCerts is the Environment Agency's Monitoring Certification Scheme. The scheme provides for the product certification of instruments, the competency certification of personnel and the accreditation of laboratories based on international standards. It aims to improve the quality of monitoring data delivered by operators of regulated processes, and assures users of certified instruments and services that they meet performance standards set out in current international standards and the growing requirements of EC Directives. In the UK accreditation is undertaken by the United Kingdom Accreditation Service (UKAS). The MCerts performance standard provides an application of ISO/IEC 17025 specifically for the chemical testing of soil and covers:

• performance targets;

• the selection and validation of methods;

• sampling pre-treatment and preparation;

• participation in proficiency testing schemes;

• the reporting of results and information.

 

The Environment Agency will only accept analytical data from laboratories who are accredited under the MCerts Chemical Testing of Soil scheme. There is currently no provision for MCerts accreditation for the on-site sampling of soil or water, thought this is something that QROS and is actively working towards. However they do state that;

“The use of in situ testing to complement MCerts laboratory analysis can significantly improve the quality of site investigation and can reduce the cost of both site investigation and remediation. It can be used for improved targeting of conventional sampling, better spatial delineation of contaminated areas, and the development of conceptual site models. Although only MCerts accredited data can be used to support regulatory decisions the Environment Agency recognises that in-situ testing has an important supporting role to play.”

 

There is however ample data that shows that one MCerts result is not the same as another MCerts result from a different laboratory using a different method. The current rules allow a +/- 30% variance for TPH and PAH from the accepted mean result on certified reference materials in the proficiency testing scheme and still retain MCerts accreditation. This means that for a sample with a nominal 1000 mg/kg TPH (the limit between hazardous and non hazardous) the range of correct results within the MCerts scheme is 700 to 1300 mg/kg. This shows that within this range a result that is around half that of another result could in fact be identical. In several cases different extraction techniques can for real samples show a variance of as much as +/- 300%.  The same problem arises with metals analysis, but the MCerts limits are much tighter at +/- 10% (+/-15% for Hg, As and Se) For further information see he following links

 

Environment Agency - Chemical testing of soil

Environment Agency - Performance Standard for Laboratories Undertaking Chemical Testing of Soil

 

UKAS (United Kingdom Accreditation Service)

The United Kingdom Accreditation Service is the sole national accreditation body recognised by government to assess, against internationally agreed standards, organisations that provide certification, testing, inspection and calibration services. Accreditation by UKAS demonstrates the competence, impartiality and performance capability of these evaluators.

UKAS home page