A bumpy ride ahead

The challenge of how to reach the Water Framework Directive’s required ‘good ecological quality’ by 2015 is exercising minds in water utilities and regulators.

Severn Trent’s Changing Course report points out that the industry has borrowed £33B since 1989, mostly to finance legislation-driven improvements and asset replacement, but that borrowing on this scale should not and probably cannot continue.

The search is on for low capital solutions, which must also be low carbon. Real time control of processes and water supplies is now firmly on the agenda as one possible means of getting good value for the environment whilst reducing energy use.

This will require solutions which deliver best ecological outcomes from controlling discharges and abstraction at a whole catchment level. The key is to enable ‘trade’ between different discharges and sources and to vary consents in real time according to prevailing conditions. Initial technical guidance on how this could work is being considered by the UKWIR project WW02 ‘Chemical Source Apportionment under the Water Framework Directive’ due to report in September 2010.

Much of the technology to implement real time control across catchments exists: hydraulic, process and river impact models; rainfall radar; flowmetering and water quality instrumentation. For sewage treatment there are gaps in the instrumentation for organic load, ammonia and phosphorous concentration.

These measurements can now be made reliably on final effluent samples, but are less successful when applied to settled sewage and crude sewage. This is of great importance as the real time control schemes will require the capability to feed forward the influent conditions and plants will be required to treat sewage to a varying effluent standard over a range of influent flows.

The new consenting arrangements will not be simple and must take into account the limited range of controllability of the biological processes in sewage treatment.

Through the WRc Instrument User Group, Portfolio collaborative research projects and the WRc Approved scheme, WRc is already supporting and promoting the use and development of the sensor technology for new and challenging applications in the water sector. For example, WRc plan to develop an optical non-contact sewage load sensor for feed-forward control of activated sludge plants.

The sensor uses laser light to interrogate a flowing sample in an open channel and is therefore immune to fouling, which is the primary cause of poor reliability of wastewater instrumentation. The project, with the support of several water companies, will develop the method in the laboratory, then build and site test a pre-production prototype. By involving the end users throughout the development, issues such as performance requirement and total cost of ownership are taken into consideration at an early stage.

Experience of developing new instruments and equipment at WRc has been that 3 years is an absolute minimum from the proving of a new idea at research level to a new commercial product, more than five years is more typical.

Without doubt there are sensor technologies in use within other sectors that could go some way to meeting the challenges within the water sector.

However, successful technology transfer will require engagement by the water companies and the Environment Agency, who must proactively take the lead and demonstrate to the sensor community that a viable commercial market exists before manufacturers and suppliers invest.

The Sensors & Instrumentation Knowledge Transfer Network, has seen significant success in the transfer of technology within the medical, automotive and energy sectors, however, the water sector has not engaged and capitalised to the same level.

Perhaps the water companies should take a lead from innovative companies in other sectors and adopt a more open approach to innovation by, for example, publishing a ‘wish list’ of sensors needed and use this to stimulate the supply chain.

Beyond the technical challenges, the organisational ones are serious. Having talked dreamily of ‘flying by wire’ and the benefits of automation since the 1980s, as an industry, we are now going to have to do it and this will be a major cultural shift.

However, there are encouraging signs of real commitment to new methods such as the United Utilities control system at Lancaster Wastewater Treatment Works and the Yorkshire Water rtRIVERi pilot on the river Don catchment. Catchment real time control also poses a challenge for regulation.

The England and Wales model of regulated private water monopolies was not designed for close cooperation and working relationships will need to be transformed in the search for solutions.

For people with an interest in real time control, these could be exciting times. It is reminiscent of the ‘great stink’ and the final adoption of Bazalgette’s transforming technical solution. We are highly constrained, seeking simultaneously to: redress industrial damage to the environment; improve drinking water quality; burn less carbon; avoid major capital spend. Real time control across catchments does tick all these boxes, but the technical and organisational challenges should not be underestimated.