Planning for the bigger picture
Paul Cherry, a member of the MCERTS project steering committee, explains how the new system works and looks at the higher legislation the scheme can be designed to serve
In January 2004, the Environment Agency (EA) extended its monitoring certification scheme MCERTS to cover the self-monitoring of effluent flow. Under the new scheme, consent holders (processors who have been granted consent to discharge by the EA) must have their sites certified by a qualified MCERTS inspector whose job it is to check flow structures and instrumentation comply with the relevant legislation.
All qualifying sites must be certified by March 2005, so water companies need to get to grips with the new requirements. However, as admirable as the new MCERTS scheme is, it is only the first step to overall compliance. The Urban Waste Water Treatment Regulations 1994 and Water Resources Act 1991 contain provisions allowing the EA to set specific consent requirements particular for each site, which can go further than requiring data for just the rate of discharge flow and cumulative daily volumes.
Other site process flow diurnals, storm flows and intermittent discharges (storm events) may also need to be monitored and reported on a regular or periodic basis. While these may not be included in MCERTS, they are still a legal requirement. In this article Paul Cherry, a member of the MCERTS Project Steering Committee (PSC) and the first qualified MCERTS inspector, explains how the new system works. The author sounds a note of caution, highlighting industry should not lose sight of the higher legislation that the scheme can be designed to serve. He also notes there could be considerable cost-savings in the long-term for water companies that plan towards the bigger picture, rather than immediate MCERTS requirements.
The EA requires consent holders to install and maintain equipment to measure and record instantaneous and cumulative daily flows at discharges above 250PE or have a dry weather flow (DWF) equal to or greater than 50m3/d. Successful effluent flow monitoring depends on operators embodying correctly applied installations, combined with appropriate equipment, calibration, maintenance, quality assurance and data management.
These should be managed within a quality system that can be routinely audited to ensure performance can be maintained over time. The MCERTS self-monitoring scheme sets minimum
- flow structures and devices, for example, flumes/weirs/ electromagnetic meters,
- monitoring equipment, for example, level sensors,
- data gathering and transmission, for example, analogue to digital,
- associated quality assurance systems, all of which are to be inspected and verified by the appointed (third party) MCERTS inspector.
The scheme operates as follows – an MCERTS inspector is contracted by the consent holder to provide an independent assessment of each site and the quality assurance system. The inspector makes a detailed analysis of the flow measurement installation and prepares a report putting forward his or her expert opinion as to whether or not the site meets the MCERTS standard. Vendor-neutral recommendations for remedial work may also be made.
On the basis of the inspector’s successful report, the MCERTS inspection body issues a certificate for the site in question, valid for five years. At the moment, MCERTS primarily focuses on DWF in and out of the site. It does not embrace measurement of storm overflows (intermittent discharges) or settled storm flow figures. The EA specifies the quality and quantity of requirements for discharges including flow. However, Ofwat has the responsibility to ensure adequate wastewater collection and treatment provision in each area and, with it, the authority to require water companies to increase their treatment capacity according to rainfall and population
figures. This is a legal requirement under the Water Industries Act – something water companies should not lose sight of in the rush to achieve MCERTS certification.
While the EA is taking a one-step-at-a-time approach to enforcing regulations, a few more progressive, leading water companies are saving significant resources by keeping their focus on the wider legislation. Investing in more intelligent solutions now, which provide total flow and compliance data not just the immediate MCERTS requirement, puts them ahead of the game. For example, MCERTS requires: “The location of the flow monitoring installation shall ensure representative measurement of the total volume discharged.” (Minimum requirements for the self-Monitoring of effluent flow, paragraph 3.2.2).
On many sites, the most obvious solution may be flow measurement at the outflow. However, an inlet measurement, downstream of the storm overflow flume, may also meet the requirement and, by including data logging equipment, a single installation could be set up to provide both total daily volume (to MCERTS) and storm overflow event data. Although the initial investment would be marginally greater, there would be significant long-term savings due to combined legal requirements being achieved at once. MCERTS says: “The total daily volume of effluent must be measured with a target uncertainty of better than ± 8% and a confidence level of 95%.” (Minimum requirements for the self-monitoring of effluent flow, paragraph 3.2.1). This can sometimes be somewhat misleading because they apply to the entire flow measurement system, not just to the primary flow structure and secondary instrumentation.
For complete legislative compliance, it is the ultimate data recorded at the data archive, which must achieve the ± 8% criteria. On the majority of sites, data acquisition systems include some sort of telemetry or other data network and acquisition and analysis software, which, by definition, must introduce some error to the final data.
It is therefore essential to check the accuracy of the combined system, including the signalling network and software, to ensure compliance. The EA describes MCERTS as being there to provide assurance about the reliability of flow measurement data to all stakeholders and to establish a level playing field in the competitive flow measurement market.
The scheme will do this, and more, not least in helping to raise professional standards in flow auditing. MCERTS does not replace all previous legislative compliance requirements. The EA’s own pioneering P150 document and ‘Procedure for flow measurement of discharges’ (September 2000) are still the fundamental basis for the interpretation of the Water Resources Act 1991.
The much wider and far-reaching obligations for consent holders described in these documents, along with specific site consent conditions, are still enforceable by the EA.
There is a strong business case for a long-term, balanced approach to planning and compliance. For water companies who make this the basis of their business strategy, MCERTS compliance is one complementary component, of a long-term plan
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