Coca-Cola Bottling Plant, Wakefield, United Kingdom
Coca-Cola’s Wakefield facility is the largest of six major bottling plants the company operates in the UK. The plant recently completed an upgrade of its water treatment facility – with Severn Trent and Norit working to provide a comprehensive purification and recovery system – which increased influent quality and upped supply capacity by over 30%. In addition, the solution selected – membrane ultra-filtration (UF) – represents a significant departure from the company’s traditionally established multi-barrier approach to water purification.
The project increased water treatment peak capacity from an hourly 300 m³/hr to 400m³/hr, improved efficiency to approaching 99% and achieved a tenfold reduction in wastewater generation – down to an average 60m³/day.
The total project cost was £1.6m to design, manufacture and install the new filtration and wash-water recovery system.
Housing nine production lines, with the capacity to produce 4,000 330ml cans and 3,200 PET bottles per minute – ranging from 500ml to 3l – and home to one of the fastest two-litre filling lines in the world, the Wakefield plant is also a regional distribution depot for the UK. 25,000 pallets are stored at the facility and as many as 250 lorries leave daily.
The pre-existing water treatment system was built in 1989, in accordance with the then standard Coca-Cola multi-barrier policy, using polyamide coagulation and sand filtration, with de-chlorination achieved through carbon filtration.
When the decision was made to upgrade the facility, in addition to providing the improved capacity, the new system was required to meet the standards laid down in the Coca-Cola ‘red book’ which applies to the raw water input at all of the company’s factories worldwide. This sets exacting quality requirements – including a total chlorine content of less than 0.05 mg/litre and turbidity below 0.2 NTUs.
The Wakefield plant is mains-fed from a Yorkshire Water surface WTP. The influent is stored in two 850m³ storage tanks before being pumped to four activated carbon tanks and then passing through an ion exchange unit which forms the facility’s organics scavenging system – organic content being a key parameter in product make-up water.
From here, the water flows to the ultra filtration system, consisting of four skids with the capacity to process 9,600m³/day – with a combined normal throughput capacity of 400m³/hour.
Each skid comprises six tubular modules, holding 24 of the 1.5m × 250mm membrane cartridges, the 0.8mm diameter hollow fibres contained within having a filtration pore size of 0.03 microns. With over 10,000 fibres per cartridge, the effective filtration surface area of each is 40m². Every three hours each of the skids – in turn – is automatically taken out of service and back-washed, with the flow rate through the other skids increased to 133m³/hour to maintain the required supply to the plant.
The backwash is based on double forward flow over a 30-second cycle, regularly putting around 250m³/hour through the skid; the backwash water is then itself cleaned for reuse via a recovery UF system.
Once every six days each of the skids also receives a chemically-enhanced back-wash, with a ten-minute period of soaking.
The UF permeate subsequently passes to semi-treated water tanks and then undergoes a final treatment process of de-aeration, cartridge filtration and UV sterilisation prior to supplying the bottling lines.
Control is SCADA-based, a single-screen system displaying all the relevant operational information, including flow, temperature, pressure, pH, turbidity and chlorine levels across all stages of the process. Operational efficiency and maintenance considerations have also been taken into account during the plant design with all the pipe-work and valves being located at low level. In addition, each membrane is automatically tested each day and can be isolated for repair as necessary without compromising the rest of the plant’s operation.
Whereas the previous plant achieved around 90% wastewater recovery – generating some 700m³/day of waste, the new system achieves significantly higher efficiency and has reduced the effluent to routinely less than 60 m³/day. This represents both major operational advantages and considerable cost savings over the year.
The plant owners are Coca-Cola Enterprises. Severn Trent Water Services was the main contractor on the project; Norit Membrane Technology supplied the UF membrane treatment system, with its sister company, Norit Südmo supplying the necessary stainless steel valves.