Managing the Flow – The Maintenance Challenge
From biological treatments to combining new technologies, the water industry is always trying to evolve. Dr Gareth Evans looks at how the sector is adapting to meet demand and what these developments mean for the future.
The water sector faces ever-increasing challenges in the 21st century, not least in terms of upgrading infrastructure to adequately meet demand, ensuring security of supply and safeguarding continuity of service. Against a combined background of ageing plants, a growing population, increasingly stringent regulations and a tighter fiscal environment, meeting these challenges was never going to be easy.
A recent report by the UK's Council for Science and Technology concluded the industry needs to invest more in technology and that "the regulatory regime militates against research and development and provides insufficient rewards for innovative solutions". It's a Catch-22 situation, and not one that applies solely to Britain.
Throughout much of its history, the industry has been caught in a cycle of renovation and expansion projects and today is no different - retro-fits, upgrades, renewed construction and technological improvements are scarcely novelties.
Moreover, as the likes of California's Alvarado water treatment plant illustrates, 'future-proofing' is a relative – and temporary – concept. Commissioned in 1951, the plant forms what the San Diego County Water Authority describes as the "heart" of the city's drinking water provision. The original design supplied water for more than 40 years before its first modernisation began in 1993. The double award-winning work ended in 1997, the same year an issue of compliance order from the California Department of Health Services mandated further modification.
Phase IV of the plant's ongoing capital improvement programme, which will see the addition of a new ozone disinfection system, is scheduled for completion by the end of 2010, with Phase V set to extend the project beyond 2013.
After 15 years and more than $300m, the finished result will be a state-of-the-art facility with a useful life of 75 years, but with a growing population and tightening quality standards, that may only buy 15 or 20 years of 'future proofing'.
The industry seems, then, to be destined to keep looking over its shoulder to stay ahead of whatever is coming next. Done well, it is an effective strategy, but as Water UK's CEO Pamela Taylor said at a recent Institute of Water conference in Belfast: "Success has been down to two things: good management and high investment."
Quality and environmental standards inevitably drive many plant renovations, and some water companies have used green technologies to achieve these goals.
"It's one of the biggest changes I've seen over my time," says retired water engineer Alan Boulanger. "When I started out, things were pretty established and mostly mechanical, but the last few years we've seen all sorts of different approaches being mooted. They're not new as such – I mean, some of this stuff is as old as the hills – but the way it's being thought of is different. Take reed beds, for instance, who'd have thought you'd see water companies using them as much as they are now?"
The move towards such low-intensity biological solutions has an obvious appeal and there is little surprise to see increasing numbers of water companies adopting the technology to help upgrade and improve sewage treatment.
Dŵr Cymru/Welsh Water's Crynant wastewater treatment plant, for instance, recently underwent a redesign to accommodate tighter discharge consents with a 2,400m², 90l/second vertical-flow reed bed. It is a pattern that has been repeated by a number of British water companies, including Severn Trent and Anglian Water.
Having used conventional reed beds to provide tertiary treatment for years, the company recently installed an innovative floating bed at its Narborough plant in Leicester.
The scope of applications is also changing. In March, Essex and Suffolk Water, part of Northumbrian Water, announced that its Hanningfield plant would extend the use of its reed beds to include drinking water treatment. This approach is also being trialled for the treatment of ferric and alum sludge. There are plans to extend it to a full-scale, 4ha installation to supersede the plant's existing system of sludge lagoons.
More heavily engineered biological systems have also found favour in the drive to renew infrastructure, not least with the rise of membrane bioreactors (MBRs) and moving bed bioreactors. Despite a rather hesitant initial uptake, recent developments in the technology, particularly in terms of the latest submerged systems, have enabled MBR solutions to find their place in the industry.
With the arrival of systems such as the recently launched FlooBed – a suspended carrier biofilm process from Eimco – the capacity of existing activated sludge systems can be increased. FlooBed achieves up to five times the nitrogen and phosphorus removal or BOD/COD capability in some cases. Where plant footprint is at a premium and conventional expansion difficult to achieve, the growing popularity of bioreactor-based upgrades is easy to understand.
Some in the industry believe that meeting future demand will eventually see a greater use of combined technologies, united into treatment trains to enable water works to do more within their existing infrastructure framework. "We've seen a period of strong biological innovation," says industry consultant Bevan Rees, "and that's carried things on a long way, but I think the next wave will see physical treatments increasingly used to augment them."
He could be proved right. The S. Rocco wastewater treatment plant in Monza, Italy, for instance, is poised to begin using Veolia's Biothelys thermal hydrolysis process to help the plant deal with a predicted population increase of nearly 10% by enhancing its digester performance. In addition to improving biodegradability and reducing hydraulic retention time downstream, this approach will also slash final sludge volumes by around a third, enhance biogas production and reduce odour nuisance.
Elsewhere, other broadly similar initiatives, uniting disparate technologies to provide a single comprehensive solution, are also developing and it seems likely that they will become increasingly common in future.
As the global water industry gets to grips with the precarious balancing act of reducing energy use and improving quality and supplying, the need to upgrade and renovate will remain unavoidable. There will be further calls for good management and high investment, but in the end it all comes down to buying a little extra time.