Project Focus: Affinity Water in metaldehyde detection trial
A trial at an Affinity Water treatment works in Hertfordshire has demonstrated the effectiveness of modifying lab equipment for online monitoring for metaldehyde
-Monitoring will support treatment and catchment programmes for water quality
-Abstraction management will allow more efficient use of source water
-Cost of treatment processes will be optimised effectively
- Intelligent software allows GCMS to operate automated sampling and report online
- Inline filtration used to protect instrument
- Remote laboratory short-cuts lengthy lab analysis
by James Brockett
Affinity Water has taken an innovative approach to the detection of metaldehyde in a trial at a karstic groundwater treatment works in Hertfordshire with promising results.
The water-only company has been working with Cambridge-based analytical technology specialists Anatune in a trial involving their gas chromatography mass spectrometry (GCMS) instrument. The instrument, which is more typically used for laboratory testing, has been adapted so that it can conduct automated sampling at the works, providing almost real-time data to the works’ SCADA online monitoring system. Using this process means that metaldehyde results are available to Affinity’s operational team in 36 minutes, instead of relying on lab sampling which takes several days.
The trial is part of Affinity Water’s Pesticide Programme of research and development, and has been described by the water company as a ‘potential game changer’ for the industry in dealing with metaldehyde, an active ingredient found in slug pellets which makes its way into surface water and groundwater.
Currently, Affinity uses other indicators such as UV absorbance in its online monitoring - backed up by lab testing - to establish the presence of metaldehyde, and this imperfect knowledge frequently means it needs to cease abstraction from particular sources, run water to waste, or import water from other regions in order to be sure of meeting drinking water quality standards for individual pesticides (0.1ug/l).
Treatment to be optimised
The water company is set to install activated carbon metaldehyde treatment at the site by 2020, and already has a well-established catchment management programme in one catchment where farmers are voluntarily using alternative products to metaldehyde. If successful, the improved monitoring regime will allow Affinity Water to optimise the new treatment to minimise operational cost, while providing live data which can assist in its dialogue with farmers and other local stakeholders.
Since the trial began in September, the Triple Quadrupole GCMS has been operating 24/7 and is fully connected to telemetry software analysing metaldehyde concentrations from three separate inlets at different stages of the treatment process.
“This trial is very exciting and is generating a lot of interest in the industry,” says Affinity Water Asset Manager, Debbie Loftus-Holden.
“Online water quality monitoring is currently limited to parameters such as turbidity, UV absorbance, pH and nitrates – up until now, we’ve not been able to do organic analysis online. Having live data on metaldehyde available within 36 minutes is going to do two things for us. It will help us with more targeted abstraction management, so we can cease abstraction from one or more of the sources if necessary so we don’t get a metaldehyde exceedance. But it will also be upstream of the new treatment process, so we can make sure the treatment process is optimised for inlet concentrations.
“The instrument has never been installed in a treatment works before, so one of the challenges has been managing the inlet water quality to the instrument: the water at this site is karstic groundwater, which reacts to rainfall quite rapidly, and that will have an impact on the instrument. We’ve had to modify the environment for the instrument quite significantly, making sure it is kept at a steady temperature, and have also had to install an inline filtration system, a turbidity inlet of less than 1 NTU and more sophisticated software to ensure the instrument can read to our online SCADA system.“
Putting what it is effectively a remote laboratory on an operational site has meant a number of specific challenges have needed to be overcome, says Loftus-Holden. Problems associated with leaving the instrument unattended – such as broken needles and the way it copes when it encounters anomalies – needed to be set against the health and safety implications of having a lone worker working full time in the cabin.
“When this piece of kit is used in our laboratory, it doesn’t have automated sampling and there is always that manual interaction with the scientist,” explains Loftus-Holden. “So the software that is currently standard with the instrument simply gives you the results and that’s it. The novel application of what we’ve done here is the intelligent software that we’ve installed on it, and also the inline filtration system.”
Solving these challenges and getting the trial off the ground required intensive collaboration between Affinity Water, contractor JRP Ltd and equipment supplier Anatune.
Ray Perkins, CEO of Anatune, said: “Working with Affinity Water has been a great opportunity to see how our GCMS instrument can be used in other ways and we are excited by the promising results of this trial and the implications for the water industry.”
The trial started in September in order to capture the period of time when metaldehyde is typically used because of wet weather and the prevalence of slugs. The results to date are promising, with several spikes detected which were later correlated with metaldehyde use in the catchment; testing accuracy has been shown to be in line with that of the equipment used in the laboratory. The company is planning to share its detailed results with the wider industry and other water companies are monitoring the outcomes closely.
Affinity Water tested three different metaldehyde treatment technologies last year. While activated carbon is the chosen treatment solution at the treatment works where the online monitoring trial is taking place, Affinity Water is still working with other novel treatment technologies and may implement different solutions at other sites.
Meanwhile, the company’s catchment management programme has run since 2010 and was expanded in 2012/3; it covers the use of a number of pesticides and herbicides in addition to metaldehyde. It is possible that online monitoring could be extended to these other substances in future, further supporting the pesticide programme, added Loftus-Holden.
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