Water & Wastewater Treatment Magazine
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12 | MARCH 2017 | WWT | www.wwtonline.co.uk G reater stormwater separation by utilities is the key to extending the life of sewers and ensuring the wastewater network remains effective, speakers agreed at WWT's Wastewater 2017 conference. Faced with the twin challenges of climate change and population growth, water and sewerage companies can no longer afford to allow so much surface water to enter the wastewater network, where it overwhelms treatment infrastructure and leads to polluting discharges from combined sewer overflows (CSOs). "The use of our asset base is changing – foul water sewers are transferring more stormwater than they were ever designed to do," Nevil Muncaster, Director of Asset Management at Yorkshire Water, told the conference in Birmingham. "We've got to start thinking about separation, and not just treatment. Removing the stormwater problem is the key to giving us more headroom on capacity." However tackling stormwater requires new models of collaboration. Along with the Environment Agency and local authorities, Yorkshire Water has contributed to Strategic Drainage Management Plans across its region. Better drainage in an area conveys multiple benefits - a better environment as well as flood prevention - and Muncaster said that to convey these benefits it requires a different conversation with stakeholders, where people were treated as 'citizens' rather than 'customers'. The conference heard a case study of stormwater separation in action from Dr Stephen Blockwell, Head of Strategic Investment Planning at Northern Ireland Water. He outlined how Northern Ireland Water was investing £5.2M in resilience measures around Belfast, which is subject to both tidal and pluvial flooding. The pilot programme is using a powerful GIS modelling tool to identify the sources of stormwater flows, potential 'sinks' where the water can flow away and pathways where the water could be taken from one to the other. In total, 55 possible projects had been identified under the pilot with solutions considered including green roofs, swales and bioretention. "The tool gives us a standardized method we can use to identify the best opportunities to invest; it's much better than placing dots on maps or just choosing sites where politicians would like us to spend money," said Blockwell. THE SPEAKERS "Strategic drainage management planning is very much the future for our industry. SDMPs are the way we can have a different conversation where we can talk about those multiple benefits." Nevil Muncaster Director of Asset Management, Yorkshire Water "Innovation only really happens on a project if it is driven by the client – so we take this extremely seriously." Phil Stride Strategic Projects Director, Tideway "By working together you can come up with an integrated plan that will provide more benefit, but you need to get in at the very start." Richard Woodhouse Asset Delivery Programme Manager, Northumbrian Water James Brockett reports from Birmingham "A standardized method, identifying the best opportunities to invest, is much better than placing dots on maps or just choosing sites where politicians would like us to spend money." Dr Stephen Blockwell Head of Strategic Investment Planning, Northern Ireland Water Events Separation of stormwater 'key to maintaining health of sewer networks' WWT Smart Water Networks conference, Birmingham, March 21. NEXT EVENT To take away 1. Amid challenges of climate change and population growth, preventing surface water from entering the sewer network is the key to getting the best performance and asset life from existing sewers. 2. However, better drainage and separation of stormwater requires a collaborative approach. Strategic Drainage Management Plans (SDMPs) are one way of achieving this. 3. Geographic modelling tools can provide the best way of establishing where maximum stormwater diversion can be achieved for the lowest cost. 4. Building environmental objectives into any scheme is important for bringing local stakeholders on board. 5. Sustainable drainage solutions are one tool in the box when it comes to stormwater separation, but are not suitable everywhere. Building a more resilient network should be the priority for the long term.