Water & Wastewater Treatment Magazine
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In the know Getting to grips with... ice pigging 32 | MARCH 2017 | WWT | www.wwtonline.co.uk the wet well. This is usually done via an adapted non-return valve or an existing bauer fitting where no enabling works are required. The pig is then pushed along the pipe using the in-situ wet well pumps and travels to the end of the rising main, collecting fat and grit deposits. Once it reaches the outlet the ice and retrieved sediment is collected in a vacuum tanker. What problems could be solved by applying this technique in sewer rising mains? Sewer rising mains suffer from problems that are fairly unique, and o•en associated with the acidic nature of the waste they are carrying. We have seen that ice pigging is very effective at removing waste that has accumulated and that is o•en causing a build-up of Hydrogen Sulphide (H2S) which can cause corrosive conditions, and produce odours. Corrosion of wastewater pipes, both metallic and cement based, is a problem universally seen. Odours, and build-up of noxious gases are at best a nuisance for the public but at worst can be a hazard for water company staff that should be avoided. As there has not previously been a reliable and low-risk means of removing build-up of these problems, it looks like this is the first time there is an easy non-invasive solution for these two key problems. Ice pigging is also very effective at removing sand, gravel, fats and greases, and air locks from sewer rising mains that have been causing hydraulic problems may have built up over years. O•en clearing these types of blockages can bring the pipe back to its original design flow rates in a very short time, and significantly reduce the risk of the pipe failing. Could this technique help water companies to reduce the number of sewer flooding incidents that they have? This remains a key focus for all of the water and sewage companies in UK. In certain circumstances, yes. We have worked with one water company that was contemplating the complete replacement of a sewer pumping main because of its inability to cope with flow rates during rainfall events. Sadly, the wet well serving the pumping main had flooded a number of times and the sewage had overflowed into nearby domestic properties. The pipe was cleaned with ice pigging and returned to its original flow capacity, saving the water company more than £500,000 and of course removing the risk of flooding to the adjacent properties. We don't profess for this technique to help in all sewer flooding situations, but where the capacity of the pipe is in question it should certainly be considered as a fast, low-cost and non-intrusive way of solving the problem. What do you see in the future of ice pigging for rising mains? We believe that it is o•en the state of the pipe rather than the wet well pumps that is responsible for under- performing rising mains. With the apparent increase in the number of fines imposed on water companies for environmental incidents, we think more operators should look to mains cleansing as a cost-effective way to improve performance rather than the more expensive options of pump or mains replacement. The key benefits of Ice Pigging being speed, convenience and no-dig, we really feel that this service is set to be successful going forward. SUEZ are always pushing forward with new innovation and we recently conducted an operation involving crushing solid ice directly into the pipe at the point of use, allowing for the thickest, and therefore highest shear ice possible. During the course of our R&D work we have even seen success in removing Vaseline from 600mm pipes. Whilst a relatively so• substance, it is incredibly difficult to remove – by its very purpose it is employed to smear and slide rather than detach from what it is adhered to. It is developments like this that we feel can have a big impact in the sewer cleaning industry. The ice slurry in inserted directly into the pipe downstream from the wet well The ice leaving a rising main