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Real-time TOC strammer spildevand kontrol på Greencore

Total organisk kulstof monitor

A food manufacturing facility in Selby has installed a new continuous TOC (Total Organic Carbon) monitor, ‘the BioTector’ which has dramatically improved the site’s capability to refine and improve the plant’s wastewater treatment process. As a result the plant is better able to quickly respond to changes in the influent.

Greencore Foods er en førende aktør inden for fødevareforarbejdningsindustrien, og koncernens dagligvare division er en af ​​Storbritanniens førende producenter af flaskeopskrifter (herunder madlavningssaus, pickles, dips og sodavand, der producerer 200 millioner krukker om året på tværs af 800-produkter linier). Opererer fra et websted i Selby i nærheden af ​​York, producerer det en bred vifte af både mærkevarer og detailhandelsvarer inden for nøglesektorerne.

Anlægget har modtaget betydelige investeringer i de sidste 10-år og har nu nogle af de mest moderne, hygiejniske og effektive produktionsfaciliteter i Storbritannien, der opnår den prestigefyldte AIB-akkreditering og placeres i kategorien "overlegen".

The Selby site is operated on a continuous improvement basis with its own dedicated wastewater treatment plant to monitor and control effluent quality and minimise costly discharge fees. Effluent from the food manufacturing industry contains an array of inorganic salts and organic components which enter the waste stream in part from the intense wash down of processing tanks and lines during clean in place procedures for product changeover. Overload of organics on the effluent treatment plant adversely affects the efficiency of the treatment process. If the waste is not treated to the required standard, then the site will be unable to achieve the river discharge parameters that have been set by the Environment Agency.

The effluent treatment plant at the Selby facility is managed by a specialist team from Veolia Water Industrial Outsourcing Ltd. Raw feed water entering the facility, is analysed for TOC to control the strength of the feed transferred to the site effluent treatment plant.

As Greencore Environment Manager David Murtagh explains “In the past samples were manually collected from the site drains pit and transported to the laboratory at a second location. Given the geographical distance between sites this led to significant waste, both in terms of time and resources. We had a small team in the laboratory who performed a number of analyses on the delivered samples, which was quite labour intensive and delayed results. Even state of the art laboratory techniques still took too long for pragmatic purposes, preventing prompt feedback on the process. Overall, this was not 21st century and provided no direct information to control the effluent plant or provide an early warning of process issues. An alternative needed to be sought.

"En yderligere nøglefører var den forestående stramning af samtykket til udledning til flod af Miljøstyrelsen. Vi havde brug for mere hyppige, mere detaljerede, hurtige, nøjagtige og pålidelige indflydelsesfulde TOC-data for at hjælpe med at håndtere spildevandsbehandlingsanlægget mere effektivt og give feedback på processen, der er kilden til TOC. Vi var forsigtige med on-line TOC instrumenter på grund af dårlige erfaringer i fortiden; mens de fungerede godt på renere, partikelfrie spildevandsproever, var de høje faste stoffer, fedtstoffer, olier og fedtstoffer og variable TOC-belastninger, der stammer fra rå indflydelse, et stort problem for delikate fine kapillarrør og ventiler, der typisk forårsagede instrumentbeslag.

Historical issues
Traditional methods for analysis of TOC/COD/BOD were developed as laboratory systems based on UV exposure, wet chemistry or more aggressive digestion by catalysed combustion. While these provide an excellent basis for spot sampling within the laboratory where sample pre-treatment (e.g. by filtering) is controllable, the systems do not often translate well in a real process environment.

Raw effluent presents a series of challenges. With UV based systems, high salt loads can cause scaling of the UV light column creating problems or organic recovery. In high temperature combustion systems, salt loads as low as 0.5% can inhibit the persulphate digestion mechanism and deteriorate the lifetime of the catalyst, demanding excessive maintenance by replacement of the column. Sample volume is commonly restricted to less than 10µl and sample pre-filtering is necessary to avoid particulate blockage of tubing and multi-port valves such that particle size is restricted to <200µm. In a process environment, clogging of tubes with crystallised salts and particulates can demand instrument re-calibration every 2-3 days.

New Monitoring Technology
To achieve continuous, function in harsh process environments the BioTector from HACH LANGE uses a patented advanced oxidation process to offer aggressive breakdown of organics without thermal dependence. This is achieved by exposing high pH reagents to ozone. Highly corrosive unstable hydroxyl radicals are generated and by a Two Stage Advanced Oxidation this enables the system to handle very large sample volumes without the need for syringe controlled dilution mechanisms (an additional route for blockage in traditional techniques). A self cleaning facility with micro-bubbles prevents particles becoming trapped and an inbuilt salt trap allows salt loads as high as 30% and calcium loads of up to 12% without dilution. Without the temperature resistant ceramic components of contemporary systems where salt can easily crystallise and cause blockage, the catalyst within the BioTector is attached to the exterior of the furnace, extending lifetime and facilitating easy replacement.

Unaffected by fats (internal tubing is protected by back wash), greases, salts and particulates up to 2mm diameter, a representative sample is achieved without pre-filtering allowing in excess of 80,000 continuous measurements per year. Maintenance requirements are minimal (6 monthly service is recommended with no calibration demands between service). The overall result is a 99+% uptime for the end user.

Resumé
Som Veolia's Continuous Improvement Manager Marcus Hardiker forklarer "Alle tidligere bekymringer vedrørende brugen af ​​en online TOC-meter blev behandlet med praktiske løsninger. Instrumentet tager prøver fra det rensede spildevand, der føres til webstedets rensningsanlæg. Vi havde imidlertid brug for, at prøven var så repræsentativ som muligt, og derfor blev der ikke installeret in-line filtre i prøvelinjen. Prøveudtagningsarrangementet blev meget omhyggeligt konstrueret af specialistteamet for at håndtere webstedets unikke type spildevand, der indeholder højt sand og siltindhold.

“The signals from the BioTector unit have been integrated into both Veolia Water”s effluent plant control system and Greencore’s own data acquisition system. Veolia use the analysis to control the strength of feed transferred to the site effluent treatment plant. Any loads that exceed a pre-determined level are diverted to the site calamity tank. This control has enabled the performance of the effluent treatment plant to be greatly improved.

"Signalerne fra TOC-måleren overføres også til Greencore's produktionsområder, og online-dataene er synlige for procespersonale, der nu kan se, hvilken virkning deres aktiviteter har på udledningsbelastningerne, der udledes til behandlingsanlægget. Greencore har også knyttet de online-resultater, BioTector leverer til et alarmsystem, så produktionsmedarbejderne ved, når TOC-niveauerne er steget - således at de kan reagere meget hurtigere og dermed identificere og løse eventuelle problemer, når de opstår. "

With tailored solutions to match client needs, BioTector is simple to use and can reduce operational costs, avoid downtime and provide greater insight into processes for true real time control.

Author: Dr Patsy Rigby, HACH LANGE, UK

HACH

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