Water and Effluent Treatment Magazine
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SEPTEMBER 2016 WET NEWS 27 SCOTLAND'S FLAGSHIP ANNUAL WATER CONFERENCE The 5 th WWT Water Scotland Conference is the only event that brings together the whole sector to share leading case studies and strategic expertise specific to Scotland. Roseanna Cunningham MSP Cabinet secretary for environment, climate change and land reform Alan Sutherland Chief executive officer Water Industry Commission for Scotland Peter Farrer Chief operating officer Scottish Water Terry A'Hearn Chief executive officer SEPA Lucy Darch Managing director, Northumbrian Water Group Business David Grzybowski Data manager Drinking Water Quality Regulator Keith Aitken Journalist, author and broadcaster EXPERT SPEAKERS INCLUDE CHAIR BOOK NOW www.wwt-scotland.net SCOTLAND WATER CONFERENCE 5 OCTOBER 2016 | GLASGOW SUPPORTED BY SUPPORTED BY • Hear the latest on retail competition both in Scotland and south of the Border • Learn how the sector is tackling floods and SuDS through regulation, collaboration and modelling • Share ideas on how to drive a cutting-edge and efficient sector through innovation FOLLOW US @WWTlive #waterscotland PUMP HIRE & SALES SERVICE & REPAIRS DE- WATERING MONITORING & CONTROL OVER PUMPING PUMP STATIONS Option 1 PUMP HIRE & SALES SERVICE & REPAIRS DE- WATERING MONITORING & CONTROL OVER PUMPING PUMP STATIONS Option 1b The use of concrete pipes reduces risks associated with size tolerance, consistency of cross-sectional shape in straightness along a pipeline's length which can further reduce capacity. Flexible pipelines are more susceptible to this phenomenon because they tend to have a lower resistance to bending and are vulnerable to poor and inconsistent compaction of embedment. This can result in the formation of peaks and troughs along the pipe's length, resulting in additional hydraulic losses and a reduction in flow capacity. The issues of maintaining pipe shape can be eliminated through the use of rigid pipes such as precast concrete which does not deform over its service life, thus maintaining hydraulic performance. Hydraulic roughness The smoother a pipe's walls the greater its hydraulic capac- ity. Over time the build-up of slime and the accumulation of sediment can lead to an increase in hydraulic resistance and a reduction in a pipeline's hydraulic capacity. Waste water pipelines are required to perform over a long period of time, typically a cen- tury or longer. Over this length of time it is worth considering that the pipeline will only behave 'as new' for a tiny frac- tion of its life, even with regular maintenance. Instead it is prob- ably more realistic to base hydraulic designs on a degree of 'sliming', which is the case in the Sewers for Adoption docu- ment. This gives a surface roughness of (Ks) of 1.5mm for foul sewers and 0.6mm for storm sewers for all pipe materials. Even so, the hydraulic roughness of some structured wall flexible pipes can be greater than that of smooth bore pipes. This is because the outer wall of some flexible pipes is ribbed and this ribbing may, to some degree, be mir- rored on the inside wall of the pipe as a result of the manufac- turing process. A corrugated internal surface is recognised by water engineers to be less efficient and has a high hydrau- lic roughness. By contrast, the use of con- crete pipes reduces risks associ- ated with size tolerance, con- sistency of cross-sectional shape, variations in longitudi- nal profile and they do not have a corrugated internal bore. This ensures that designers and installers can more reliably determine the long term hydraulic performance of a pipeline system. n Stuart Crisp is business development director of the Concrete Pipeline Systems Association. For further information refer to the CPSA Factsheet The impact of pipe deflection on structural integrity, hydraulic performance and suitability for adoption at www. concretepipes.co.uk/downloads