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UTILITY WEEK | 24TH - 30TH APRIL 2015 | 23 • Up to 1,000 times more efficient at removing sediment and biofilm than flushing. Typically 15-20kg of material is removed per km of pipe cleaned • Significantly reduces customer disruption compared with traditional cleaning methods • Takes half the time required by other pipe-cleaning techniques, sometime less – typically the pipe is isolated for 30 to 180 minutes • It is generally a no-dig technique • Low risk to assets, environment and public health • Lowest cost per volume of sediment removed technique available on the market • The saline ice slurry can flow through all pipe diameters, fittings and around bends • Uses at least 50 per cent less water than flushing or standard pigging • For cleaning pumped sewers, energy savings and increased pump efficiency are key benefits "I know every water company in the UK is injecting water into the system at fantastic quality. But what happens to it between there and the tap?" Operations & Assets Key benefits: Tors stage 2, the proof of concept model Mat Stephenson, business unit director, Aqualogy Flushing versus ice pigging Flushing is the most common method for cleaning drinking water pipes. It involves sending high velocity water through pipes to wash out sediment. But an Aqualogy project in Australia revealed just how much dirt gets left behind by flushing. An Australian water company, which had been experiencing problems with water colouration, carried out a test to compare the effectiveness of flushing and ice pigging on a pipe that was known to contain sediment. Flushing the pipe removed approximately 50g of solids. This included 25g of organic solids and 18g of volatile organic solids – both of which could lead to the growth of bacteria. The same pipe was then ice pigged. This process removed an additional 1.7kg of solids, which the flushing had left behind. Of this, almost 600g was organic solids and 88g volatile organic solids. ice pigging is simple. It involves pumping a saline ice slurry into a pipe under sufficient pressure to form a semi-solid block or "pig" that completely fills a section of the pipe. This pig is then pushed down the pipe – in the case of water mains under the natural pressure of the system – and the ices absorbs sediment or wipes biofilms from the inside of the pipe. The ice is then pumped out of the pipe, along with the solids it has picked up. Ice pigging is now an "accepted technol- ogy" for cleaning drinking water pipes in the UK, according to Mat Stephenson, busi- ness unit director for ice pigging at Aqualogy. A key mission for him now is to see its use increase globally – the company has already led ice pigging projects in the US, Australia, Chile, Japan – and to transfer it to other sectors. However, although Stephenson says ice pigging is known by all UK water companies, he admits that it is still oen designated as a "specialist" rather than a mainstream tech- nique, despite its effectiveness. So, with the sector under pressure to increase operational efficiencies and demon- strate better whole-life asset management in the new AMP, is it something they should be using more? "It's an innovation, it's a good idea, it's not expensive and it solves problems," says Stephenson. "So yes." TM In AMP5 Northumbrian Water had a regulatory undertaking to clean 219km of large diameter mains water pipes, a programme with a £66 million price tag. Keen to explore the use of non- conventional cleaning techniques, Northumbrian Water partnered with Aqualogy to undertake the industry's biggest ice pigging project to date. The programme has been deemed a great success by Northumbrian Water, with cost savings of around £4 million and the avoidance of potential repu- tational and SIM score damage caused by traffic disruption and customer inconvenience. The most recent operation within this programme of pipe cleaning was the cleaning of 800 metres of 600mm-diameter pipe spanning the iconic Tyne Bridge in Newcastle. The pipe was installed in 1927 and was cleaned for the first time, using ice pigging, on 31 March this year. The Tyne Bridge is a busy thor- oughfare and the pipe clean was locally anticipated to cause sever disruption. In the event, the pig- ging process, which used 40,000 litres of ice slurry, was completed in 3-4 hours late at night – so disruption was minimal. Stuart Tilley, project manager at Northumbrian Water said: "Our mains cleaning programme is essential to protecting tap water for the future for our customers. "The ice pigging method has been a great addition to the clean- ing techniques we use, it allows us to clean significant lengths of water main with minimum impact to our customers and reduces the cost and time involved." Northumbrian Water case study Before Aer All photos: Peter Byrne A pipe flushed with water