Ice Pigging: Award-Winning, Advanced Pipe Cleaning Technology Paul Treloar Ice pigging, a sustainable cleaning method for potable water distribution mains and wastewater force mains, was developed in the United Kingdom and introduced in the United States in 2012. The method involves pumping a slurry of ice into a main through a hydrant, or other existing fitting, and using system pressure to push the ice pig downstream to exit through a similar fitting. The ice slurry, filling 20 to 30 percent of a pipe’s volume, cleans with shear force—between 100 and 1,000 times greater than with water alone—providing more-effective cleaning and using significantly less water than traditional flushing methods.
Introduction An ice pig works like a glacier does. Rather than bulldozing sediment and biofilm, it incorporates them into the ice. Because the ice pig enters and exits through a hydrant, specialized launch and retrieval stations are not required, as with mechanical pigging or swabbing; customer service isolation usually is not necessary either. Sediment; fats, oils, and grease (FOG); and debris accumulation in wastewater collection systems clog force mains and siphons, causing pipeline restrictions. Theses restricted flows can cause increased energy use and sanitary
sewer overflows and can lead to needed capital improvements, including increased pumping capacity and force main replacement. Other technologies, like flushing and water jetting, are inefficient and sometimes ineffective. In addition, these processes use a lot of water, which may not be readily available.
Background Developed by the University of Bristol in England, ice pigging is an innovative, low-risk, advanced pipe cleaning technology to clean drinking water pipes, sewer force mains, and siphons. The ice slurry can be inserted and removed through line taps, air valves, and other existing fittings, so expensive excavations are not required. Ice pigging harnesses the characteristics of a semisolid material that can be pumped like a liquid, but behaves like a solid once the pig is formed in the pipe Because ice pigging relies on the natural glacial effect of ice to pick up unwanted sediment, it uses approximately 50 percent less water than standard water flushing and takes significantly less time. Typically, the section of main being cleaned is out of service for no more than 60 minutes. A central feature of ice pigging is that it cannot get stuck. If for some reason that were to happen, time would be allowed for the ice
Figure 1. Ice production setup showing the delivery rig (left) and ice machines (right).
28 May 2022 • Florida Water Resources Journal
to melt and flush it from the main. Pipe bends, changes in diameter, or butterfly valves can all pose problems for swabbing or pigging, yet ice pigs can easily negotiate these obstacles. To launch and receive traditional pigs, excavations may be required to allow the installation of launch and reception stations. This can mean extensive and costly interruptions to any system and may require the installation of bypass pumping or a temporary water supply. Ice pigging is far less intrusive to any system it’s used on.
The Benefits Ice pigging represents a sustainable best practice and unique approach to pipe cleaning. The advantages include: S I t’s efficient, rapid, and environmentally friendly. S C ombines operational benefits of flushing with the impact of solid pigging. S Ice slurry injects through existing fittings. S System pressure pushes the ice. S Suitable for pipes of all sizes and materials. S E ffectively removes biofilm, iron, manganese, FOG, grit, and sediments. S Produces quantifiable results. S Exceptionally low risk.
Figure 2. A french press measures ice fraction.
