Coca-Cola opts for ultrafiltration

A Coca-Cola factory in Yorkshire has slashed its water wastage and cut costs by calling in Norit Membrane Technology to install an ultrafiltration membrane system. Natasha Wiseman reports

Coca-Cola Enterprises (CCE) has made a departure from its usual multi-barrier approach to water treatment at its soft-drinks plant in Wakefield in Yorkshire.

Purification specialist Norit Membrane Technology (NMT) has installed an ultrafiltration (UF) membrane system for water purification and a recovery system for backwash water, as part the transition from traditional treatment.

The upgraded water treatment plant (WTP) at CCE's site in Wakefield, manages supply for the producer's biggest production facility in Europe, with ten production lines producing 4 million cases of soft drinks a year and capacity for 12 million.

The manufacture of soft drinks requires large volumes of water, which are treated at the on-site WTP to meet quality requirements before being used in the production process. The incoming water from the mains, which is high quality with low organic levels, is stored in two 800m3 storage tanks.

From there, it is pumped to four 18m3 activated-carbon tanks containing a total of 66m3 of filter medium. The tanks are 2.6m in diameter and 4m high, providing and empty bed contact time (EBCT) of 10 minutes.

A continuous flow of 200m3/h then passes through three organic scavengers before being pumped to the NMT skids. The membrane UF system consists of four skids capable or processing 7,000m3/d, though the combined normal throughput capacity is 400m3/h, which allows for downtime for maintenance for one skid at any time.

Each skid consists of six 316 SS tubular pressure valves, housing a total of 24 SXL 225 Norit X-Flow membrane cartridges. Each cartridge is 1.5m long and 200mm in diameter and contains more than 10,000 polymeric hollow fibre filters.

The filters are 0.8mm in diameter with a filtration pore size of only 0.03µm providing a better quality water than the previous system. This gives an effective filtration surface area of 40m2 for each cartridge and the technology is effective in removing 99.99% of viruses and 99.9999% of bacteria, including waterborne cryptosporidium.

The filters are cleaned regularly by forcing water back through the filter for backwashing. To improve water efficiency and reduce the demand on the mains supply, the new system recycles the backwash water through the treatment plant, allowing it to be reused.

Every 40 minutes, the skids are automatically taken off the line and backwashed with cleaned water for 40 seconds. During this time the throughput of water in the remaining skids is increased to 133m3/h in order to maintain the required 400m3/h supply to the plant.

Each skid is automatically taken off the line every three hours and backwashed with cleaned water for 30-40 seconds. During this time, the throughput of the water in the remaining skids is increased to 133m3/h in order to maintain the required 400m3/h supply to the plant.

Despite their tiny size, the hollow fibres are extremely robust and designed for continual operation and cleaning. However, should damage occur, leaks can be detected through a built-in air pressure testing process and repairs carried out. Tests are carried out daily and, should a leak occur, the skids can be taken out of service with negligible impact on the efficiency of the system.

Minimising water wastage is a key part of the system's strategy and only 3% of the water goes to waste. About 8m3/h of wash water from the carbon filter and the UF modules is pumped to a 60m3 holding tank before going through the water recovery system. This has a 10m3/h capacity and incorporates Norit's Aquaflex membrane system consisting of four vertical modules.

Throughout the project, NMT worked closely with its sister company Norit Südmo, which supplied all the stainless-steel valves for the water treatment plant. A bespoke Scada HMI (human machine interface) system was developed in-house to integrate the WTP into process software controlling the whole plant.

Total investment in the plant was £1.2-1.4M with the membrane filtration and washwater system comprising £300,000 of the total. Decommissioning of the old plant has reduced footprint by 50%, while flow through has increased by 50%.

The new system offers important benefits not only in terms of water quality but also cost savings through the efficient water recovery process. The whole plant operates automatically. CCE now says that UF is the minimum standard for its new facilities and retrofitting of its older plants.

CCE's local water treatment expert Dave Lumb said: "This system is a departure from our traditional water purification methods, and the results are very promising. With our previous system we had an overall throughput yield of only about 90%, sending over 700m3 of water to waste every day.

"Not only is this expensive, but Yorkshire Water's downstream processing costs unnecessary energy. By comparison, the new system has significantly increased efficiency to over 98%, providing a 30-fold reduction in wastewater."

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