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First, there was water. The system, known as flushing, consists of pumping water into pipes at high pressure to flush away particles. But this consumes too much water and becomes more inefficient as the diameter to be cleaned becomes wider. Then came air. Too aggressive for the pipe walls and ineffective. It was so badly received that it was never given a proper name.
A PARADIGM SHIFT
Later came swabbing, which involves dragging the sediments away with an object known as a pig, introduced into the pipe from the outside. Effective but expensive, and limited by the possibility of the pig becoming blocked or lost in the network. This system did not fulfil expectations either.
Then it was the turn of ice. Or ice slurry, to be precise. It is known as Ice Pigging and has brought a paradigm shift to the cleaning and maintenance of underground pipes and drains running through cities, which is what we are concerned with.
In the intricate network of water pipes that channel the liquid, sediments are deposited over time that can muddy, spoil or even pollute the water. Assuring acceptable water quality is a real challenge for water companies who must set aside a large proportion of their budgets to deal with this issue.
Taking the example of the United Kingdom, we can get some idea of the problem. Ofwat, the water regulator, has established that the success of the performance of a drinking water supply company depends on quality as perceived by the consumers.
Any firm failing to comply with requirements in terms of colour, turbidity and iron and magnesium content is penalised through the rates they charge their customers.
It is not surprising, therefore, that it was in Britain where Ice Pigging was invented. Scientists and technical experts at Bristol University researched for over a decade until they developed a system, which is in fact quite simple to describe. You inject ice slush into the pipes through a hydrant, pump it by using the natural pressure from the channels in the network and by harnessing its rheological properties (flow and adaptability). This enables a compact mass to be formed which adapts perfectly to the shape of the pipes and scrapes the walls as it moves along the pipe. At the end of the stretch, the ice slurry is
recovered through another outlet hydrant. It is as simple and fast as that: the complete operation takes no longer than two hours - that is how efficient it is.
To make the operation even simpler, Aqualogy has designed a truck to transport all the components required, from the ice factory to the cleanliness tester, including the injection pump, the storage tank and even its own power generator. Any town council wishing to employ the services of Ice Pigging need only grant the required licences, provide a site for the location of ice-generating equipment, a nearby drains network to allow the better quality wastewater to drain away and a small team of workers to operate the valve opening and closing at the injection and evacuation
points. The results obtained are certainly significant from several perspectives. Ice Pigging is kind to the environment because it uses moderate amounts of water (up to ten times less than water pressure methods), it is risk-free and does not require prolonged disruptions to service, it does not produce blockages, it is less costly and it adapts to any topology and size of pipe in the network. In fact, it has been successfully tested on pipes of up to 600 mm in diameter and on drain networks over 3 km long.
A PROMISING FUTURE
But, above all, it guarantees perfectly clean pipes that will remain clean for many years. It is ideal for water channels with problems of turbidity, sedimentation, sludge, sand, dissolved solids, biofilm, legionella and
alterations to odour or taste. The system not only returns the water to its highest quality, but it also improves public health conditions through the elimination of elements that foster the growth of bacteria and other microorganisms.
And its possibilities haven’t yet reached their limit. The possibility of adding other components to the ice to perform disinfection tasks is only one of the variables currently at the research and experimentation stage.
Ice slush still promises new and extraordinary benefits.
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