Water & Wastewater Treatment

WWT March 2017

Water & Wastewater Treatment Magazine

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www.wwtonline.co.uk | WWT | MARCH 2017 | 31 Phil Pettit InTeRnATIonAl ACCounT MAnAgeR, SueZ AdvAnCed SoluTIonS uK ice and easy for wastewater networks An innovative method of cleaning pipes, ice pigging is now being seen as a viable option for wastewater as well as clean water networks In the know Getting to grips with... ice pigging Ice pigging uses an ice slurry which is pushed into water or wastewater networks What is ice pigging? Ice pigging is a pipe cleaning process for pressurized water and wastewater rising mains that uses a slurry comprising of solid ice crystals in a liquid matrix. This is injected into the pipe to be cleaned via existing fittings such as tappings, branches or access points to form a semi-solid 'pig', which is then pushed along the pipe using the normal pressure in the system. The primary benefits of ice pigging are that it carries virtually no risk, is fast - meaning outages are kept to an absolute minimum – and can be performed over long pipe lengths where other techniques such as jetting can't be used. How was ice pigging invented? Ice pigging was first developed in 2001 by Professor Joe Quarini of Bristol University whilst looking at alternative pipe cleaning methods for the food industry. He found that a slug of ice could generate a wall shear "cleaning force" similar to that of a conventional foam pig, whilst the two- phase properties of ice slurry meant the pig could deform and flow around obstructions such as severe changes in diameter and partially closed valves. How did it cross over from the food industry to the water sector? Despite the food sector being the first target, it was soon discovered that potable water networks were very well suited to the technique. The high average age of networks means there are significant opportunities for fine sediments such as iron and manganese oxides to accumulate. These sediments represent a serious problem for water companies as they can be entrained by changes in the flow regime, potentially resulting in large fines or enforcement action by the regulator. The other key factor is that the fluidity of the ice pig can easily navigate unforeseen changes in the pipe geometry or features that are not shown on GIS. Early trials were carried out in 2008 by Bristol University and Bristol Water and since then it has gone from strength to strength in the UK water industry and in many other countries around the world. Is the process the same for wastewater pipes as it is for drinking water pipes? Although ice pigging has been heavily used for drinking water pipes (over 4500km cleaned around the world), we see similar potential for wastewater rising mains. When applied on wastewater rising mains, the process has some key differences. The first is that we never connect equipment used for wastewater pipe cleaning to drinking water pipes, to completely remove any chance of cross contamination. Although the ingredients in the ice are the same, the ice used in wastewater pipe cleaning tends to have a higher ice content and is thicker in nature. In wastewater pipes, we are looking to remove contaminants that are adhered more strongly to the pipe wall and so the ice we use is able to apply a stronger shear force than that needed for drinking water pipes where loose sediments are the predominant contaminant. In wastewater pipes, the ice slurry is inserted directly into the pipe immediately downstream from

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