Water Journal : Water Journal June 2015
WATER JUNE 2015 58 Case Study: SUEZ environnement GET FLUSHED Ice-pigging solves Port Macquarie’s biofilm build-up L ate last year, after nearly eight years of operation, the pipes servicing a Port Macquarie Reclaimed Water Treatment plant that recycles sewerage for domestic water use needed a thorough clean, along with other parts of the Council’s potable water system. Port Macquarie-Hastings Council engaged SUEZ environnement Australia to undertake the project using a method of cleaning water pipes known as ice-pigging. This is a relatively new way of cleaning waste and water pipes using slush ice. It has been found to be significantly more effective, efficient and environmentally friendly than traditional techniques. Ice-pigging is a combination of the “flushing” and “pigging” methods, adopting the main principles behind these two processes. The ice can be flushed through the pipes from any access point, typically a fire hydrant point, meaning there is no requirement for excavation and the installation of pigging entry and receival stations. The project with Port Macquarie-Hastings Council was part of a three-week cleaning contract in December 2014, to rid part of the Council’s underground system of dirt and grime, known as biofilm. Over the years, biofilm had built up across the inside of the pipe system. In fact, it was so bad in the rising main pipe that transfers water from the tertiary ponds to the reclaimed water treatment plant, that it was detaching and blocking the initial straining filter at the plant. Because of this, Port Macquarie-Hastings Council staff were manually cleaning the strainer up to three times a day in summer. According to Council’s Water and Sewerage Operations Manager, Terry Randall, a total of 33.8km of water main was cleaned with ice- pigging over a 12-day period in the Laurieton and Dunbogan areas, 30km south of Port Macquarie. “This area was chosen as it has historically had a large number of dirty water complaints, due to being at the end of our long network, old pipe work, geography (many mains have low points) – and we have an unfiltered supply,” Mr Randall said, adding that complaints had dropped considerably since the ice-pigging project had been undertaken. About 10 tonnes of ice was flushed through the system each day, through pipelines of various sizes – from 100mm to 300mm – made from materials such as PVC, ductile iron and unlined cast iron fittings. Mr Randall said ice-pigging was a thorough cleaning process: “When you see it in action, the colour of the water is incredible. It is also a systematic approach, cleaning from the source to the customer,” he added. This ensures that once a water main has been cleaned, from that point on only clean water is produced in the pipeline. There is no risk of dragging contaminants into the pipeline just cleaned, which offers a significant advantage over traditional foam-pigging. A big plus for ice-pigging, from the point of the ratepayer, is that it can clean large areas in a short space of time, which means minimal impact for water interruptions and water quality for customers due to the efficiency of the process. And unlike the traditional foam- pigging that Council has historically used to clean the pipes, there was no excavation needed. Another factor that led the Council to opt for ice-pigging is that it is kinder to the environment, as it requires about 50 per cent less water than flushing alone. It is also non-toxic and risk free, good news for the people of Port Macquarie. From a financial perspective, while on the surface it may look more expensive, it proved to be the lowest cost option considering the amount of sediment that needed removing. Using ice-pigging, SUEZ environnement Australia was able to thoroughly clean the main pipe at the Port Macquarie recycled water treatment facility within a day, and then move on to other pipes in the Council’s potable water network. Customer complaints in the area have dropped and the water is running clean. According to Terry Randall, Council is now considering using the ice-pigging technique to clean more – if not all – of its underground water pipes. Ice-pigging is kinder to the environment, as it requires about 50% less water than flushing alone.
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