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22 | 24TH - 30TH APRIL 2015 | UTILITY WEEK Game changer /Technology/Innovation Ice pigs can clean up Pushing a slushy slug of ice down a water pipe scrapes away more dirt and potential contaminants than traditional high-pressure flushing. Jane Gray looks at a technology that is gaining ground in the water sector. C ontamination – it's a water company's worst nightmare, and one they strin- gently guard against with exhaustive water treatment processes. However, once water is released into the network, it is difficult for water companies to retain control and knowledge of its qual- ity. This is made worse if their pipes are full of sediment and bacteria-breeding biofilms, which at best discolour water – alarming customers – and at worst lead to potentially harmful disinfection by-products such as trihalomethanes. The truth is that the insides of many of the UK's water pipes look pretty unpalatable. It is well known that parts of the water infra- structure are ageing and that condition mon- itoring of assets needs to be improved. With old pipes, burst mains and leaks happening all the time, with the best will in the world, water companies cannot guarantee that the environment outside their pipes does not get inside at some point between treatment works and tap. Furthermore, due to the natural chemis- try of water, even if a water company is fully confident of the cleanliness and condition Operations & Assets of a pipe at the time it is installed, deposits – most commonly of manganese and iron – can build up over time causing widespread discolouration if agitated. All this makes pipe-cleaning initiatives necessary. Yet there are still many stretches of the water network that have not been cleaned since their installation – sometimes 100 years ago. It is also questionable how effective conventional methods of cleaning – mainly flushing – are at removing grime. Ice pigging could hail a revolution in pipe cleanliness, not just for drinking water pipes but also for pumped sewers and the oil and gas industry, according to advocates. Impor- tantly, it could also help water companies reduce disruption to customers and main- tain their vital service incentive mechanism rankings. What is Ice pigging? Developed at Bristol University to improve the efficiency of pipe cleaning in the food manufacturing industry, ice pigging was first trialled by Bristol Water in 2008. In 2010, Aqualogy (which was set up by former Bris- tol Water shareholder Agbar) introduced its first commercial service for ice pigging in the water industry. Like so many really effective innovations, STEP 1 Isolate the main. This is done by closing valves upstream and downstream of the pipe section to be cleaned. This section can be up to 3km long. STEP 2 Insert the ice. The ice in slurry form has both liquid and solid qualities, enabling it to form an effective pig in a variety of pipe diameters. The slurry is pumped into the pipe via a fire hydrant or similar. The downstream pressure is monitored to allow an ice "pig" to form in the pipe. STEP 3 Open the upstream valve. The ice is pushed along the pipe under the natural pres- sure of the network when the upstream valve is opened. As the ice flows through the pipe, it presses on every surface. It absorbs sediment and wipes away biofilm. STEP 4 Collect the ice pig. Water in front of the pig is discharged normally and the ice containing pipe sediments or biofilm is collected separately. Collected solids can be analysed. STEP 5 Flush and return to service promptly. The process is efficient, rapid and exception- ally low risk. HOW DOES ICE PIGGING WORK?