iv MCerts Focus
Personnel Certification – manual stack-emission monitoring
The scheme was launched in 2000 and provides for the competence certification of personnel involved in manual (periodic) stack emission monitoring. The EA requires that manual stack-emission monitoring on processes it regulates is carried out by accredited laboratories and certified personnel. The scheme provides for the examination and assessment of personnel competence at 3 levels (Trainee, Technician and Team Leader). The scheme ensures that monitoring is carried out safely and in accordance with established methods and procedures.
Product Certification of Continuous Water Monitoring Systems
Performance standards for Continuous Water Monitoring Systems were published in 2003 and include automatic wastewater samplers, on-line analysers (covering a wide range of parameters including pH, turbidity, dissolved oxygen and TOC) and flowmeters.
Self Monitoring of Effluent Flow
The effective environmental protection and management of water bodies receiving effluent discharges requires knowledge of the mass release of pollutants. This is achieved by combining flow measurement data (volume/time) with pollutant concentration (mass/volume). The objective of this scheme is to ensure flow data monitored, recorded and presented to the EA is accurate. Total daily volume of the discharge specified in the Environmental Permit shall be measured with a target uncertainty of better than ±8%
Structure of the MCERTS scheme
MCERTS is an accredited certification scheme operating in accordance with the ISO/IEC 17000 series of conformity assessment standards.
The Environment Agency has appointed Sira Certification Service as the certification body to operate MCERTS. Sira is independent of all the interested groups, including the product manufacturers, the process operators and the regulator.
MCERTS Performance Standards for products
MCERTS Performance Standards specify the performance criteria for the specific product category. This includes fixed and portable CEMs, water monitoring equipment, ambient air monitoring systems and software. Performance criteria are evaluated by conducting laboratory tests and a 3 month field trial on a representative process.
Typical performance criteria for an electromagnetic flowmeter are as follows:
• Response time [<30s] • Warm-up time [to be reported] • Mean error [±1.5%] • Repeatability [±1.0%] • Supply voltage [±0.5%] • Output impedance [±0.5%] • Fluid temperature [±0.5%] • Ambient temperature/humidity [±0.5%]
Accredited laboratories carry out laboratory and field tests. In some cases, manufacturers can carry out their own testing, under the supervision of Sira Certification Service.
Laboratory and field test results are reviewed by a group of independent experts known as a “Certification Committee” appointed by Sira for each certification project.
The importance of product certification
MCERTS certification requires a product to meet the EA specified performance criteria both in the laboratory and in the field. Furthermore, instrument manufacturers must demonstrate that their manufacturing process is controlled and capable of producing instruments of consistent performance. Once an instrument is certified, the manufacturer must inform Sira of any design or manufacturing changes which might affect the performance of the instrument. Sira will assess the impact of those changes and, if necessary, carry out tests to ensure the modified instrument continues to meet the specified performance criteria.
Design and manufacturing changes take place quite frequently in monitoring equipment. Product certification is critically important to provide assurance to potential users and regulators that instruments manufactured months or years after certification still meet the MCERTS performance standards. Sira ensures that the effects of such changes are assessed by conducting an annual audit of the manufacturers’ management system and by conducting recertification of all instruments on a 5-yearly basis.
pH Products Now Available with MCERTS Certification
ABB (UK) has achieved MCERTS certification for its AX400 pH measurement system. Tested in a field trial conducted over a period of 9 months on an effluent discharge at Pembroke Power Station, the AX400, coupled with ABB’s 7650, 7651, 7660 pH sensors, successfully demonstrated its suitability for use in treated wastewater, untreated wastewater and receiving water applications. The achievement of MCERTS certification means that ABB’s AX400 pH measurement systems can be used in applications such as the power industry and potable water treatment.
The measurement of pH and Redox (ORP) in high purity water applications in power plants requires a number of essential elements to achieve accurate and stable readings. These include a stainless steel flowcell to minimise static effects and a reservoir-fed reference junction that overcomes KCI depletion and blockage to ensure a stable junction potential and simple reference junction replacement for low-cost maintenance.
The 7660 system has been proven to meet all these requirements by providing accurate measurement in samples below 20 µS/cm. This is especially ideal in boiler chemistry control applications, which require close control of pH levels. For applications up to 100 µS/cm the 7651 with polypropylene flowcell and the 7653 with a reservoir-fed reference electrode option provide an economical option.
For portable water treatment applications, accurate and stable pH measurement is required for optimum control at the coagulation stage of the process to minimise coagulation costs and treated water quality.
Measuring pH in coagulation processes can be particularly difficult, due to the high level of suspended solids and significant precipitation that can block the reference junction.
To overcome this problem, an ideal pH system should include an optional flowing reference junction that overcomes KCI depletion and blockage. Other features should also include simple reference junction replacement to enable low-cost maintenance in samples that contain high levels of particulates, and the availability of a low resistance glass electrode option to provide fast response in low temperature applications.
The 7600 Series meets all these requirements. The 7651 with polypropylene flowcell and the 7653 with a reservoir-fed reference electrode are an ideal low-cost option that can be readily replaced and installed. Both systems are highly-suited throughout the potable water treatment process.
“ABB’s pH measurement systems have long been used throughout a wide range of industries to provide reliable and accurate measurement,” says Mike Sparrey, Analytical Sales Specialist for ABB’s UK Measurement Products business. “We are delighted to have achieved MCERTS certification for our AX400 pH measurement system, which forms part of our commitment to providing users with the best available techniques for their environmental monitoring requirements.”
ABB has extensive experience in the design, development and manufacture of pH measurement equipment for use in even the most challenging environments. Its comprehensive range of pH sensors and transmitters can be used in a wide range of process conditions, including high temperatures and pressures, pure water and contaminated liquids.
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