MSE Systems delivers environmental success for Branston Potatoes
Branston Potatoes’ Lincoln site and the South West site near Ilminster in the UK have installed a radical new method of water treatment which provides both operational savings and delivered enhanced environmental benefits. Both water treatment projects were constructed by Derbyshire based MSE Systems.
The cleaning and packing of potatoes has a high water usage which brings with it significant economic and environmental issues. Branston needed a safe method to recycle the water rather than continuously drawing water from a borehole and contacted the water treatment plant supplier MSE Systems for a solution. MSE Systems supplied a complete water treatment plant, based on an MBR.
MBRs combine activated sludge treatment with a membrane liquid-solid separation process. The membrane component uses low pressure microfiltration and eliminates the need for conventional clarification techniques and tertiary filtration.
The process of recycling the wash water is complex as the water has to be purged not only of the inevitable soil content but also of the nitrogen and phosphorus within it from fertilizers and from organic contamination. Other aspects of repeated water use such as chemical build up were anticipated and these were dealt with through granulated activated carbon absorption. The filtering and treatment process includes solids separation, aeration, carbonaceous oxidation and nitrification, final membrane filtering, granulated activated carbon absorbtion, ultra-violet treatment and chilling to 10oC prior to re-use. Laboratory equipment monitors the system and analyses the water which confirms environmental compliance and provides data to operate the plant.
Up to 90% of water at the South West site is now recycled, with any waste being safe to return to the public sewer system.
The MBR system is in delicate balance because the anoxic tank has zero oxygen, or anoxic conditions, being neither anaerobic nor aerobic. Nitrates within the suspension are converted to gaseous Nitrogen and lost to the atmosphere.
Organic elements are also completely removed by the process. The resulting 'clean' solid sludge is deposited to a trailer for distribution to local farms.
The membrane tank is approximately 2.5m long x 2.5m wide and houses one membrane tower comprising four Mitsubishi Sterapore™ SUR hollow fibre membrane modules. High area ratio gives low hydraulic flux rates thus maximising membrane life. The plant has a current throughput of 160m3/day. The fully oxidised and zero solids permeate allows for clean effluents which can often be reused.
The control and automation of the plant was undertaken on behalf of MSE Systems by InControl Systems using Wonderware technology. Using Wonderware InTouch SCADA and data collection, with PLC control. The InTouch SCADA which visualises the entire system was used in plant tuning as well as continuous monitoring of plant operation. As this system was already applied at the Lincoln site, the South West site was integrated to the country-wide automation architecture.