Total Organics tighten effluent for Greencore05 April 2012

Greencore Foods' plant in Selby,Yorkshire, has dramatically improved its wastewater treatment process, managed by Veolia Water Industrial Outsourcing, since installing a continuous TOC (total organic carbon) monitor.

David Murtagh, Greencore environment manager, says its BioTector, from Hach Lange, now enables the plant to respond faster to changes in influent, and so control effluent quality and minimise discharge fees.

He makes the point that effluent from the food manufacturing industry contains inorganic salts and organic components that enter the waste stream in part from the wash-down of process tanks and lines during CIP (clean in place) procedures for product changeover.

However, overload of organics on the effluent plant adversely affects efficiency of the process – so wastewater entering the facility is analysed for TOC to control its strength, prior to treatment.

"In the past, samples were manually collected from the site drains pit and transported to the laboratory at a second location," explains Murtagh. That led to significant waste, both in terms of time and resources – with the analyses being labour intensive and delaying feedback.

Murtagh also states that tightening of the Environment Agency's consent to discharge was an issue. "We needed more frequent, accurate and reliable influent TOC data to help manage the effluent plant – and provide feedback on the process ," he says.

His concern, however, was that, while on-line TOC instruments work well on cleaner, particulate-free effluent samples, it's typically a different story with high solids, fats, oils and greases, and variable TOC loads, which can be "a major issue" for fine capillary tubing and valves.

However, Hach Lange's BioTector is different. IDr Patsy Rigby, of Hach Lange UK, explains that it can handle very large sample volumes, without the need for syringe-controlled dilution mechanisms. Indeed, a self-cleaning facility, with microbubbles, prevents particles from becoming trapped, while an in-built salt trap allows loads as high as 30%.

And it's working: as Veolia's continuous improvement manager Marcus Hardiker puts it: "All previous concerns regarding the use of an on-linen TOC meter were addressed... Signals from the BioTector have been intergrated into both Veolia Water's effluent plant control system and Greencore's data acquisition system. Veolia uses the analysis to control the strength of feed to the site effluent treatment plant.

"Any loads that exceed a predetermined level are diverted to the site 'calamity tank'. This control has enabled the performance of the effluent treatment plant to be greatly improved."

Brian Tinham

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