UV solutions have long been delivering improved water quality for treatment plants but for sites with footprint constraints or hydraulic limitations, disinfection technology options can be limited. James Leigh, UV Lead, Evoqua Water Technologies, shares his insight into how innovative new technologies are opening up disinfection solutions for plants of all shapes and sizes, as well as meeting tight TOTEX costs and operating requirements.
We know space is a common project constraint faced by many water treatment plants and expanding the site is often not viable for cost, planning permission or sustainability reasons. When space is an issue, there is only one thing for it and that’s innovation. You have to think smarter, think outside the box and not be afraid to explore alternative options.
For plants wanting to improve water quality through adding a multi disinfection barrier, UV is a key solution, but the technology has been too large for some sites to date. We’ve therefore been thinking about UV in a different way. Whereas conventional UV is installed in a duty standby system, on the combined filter outlet of the disinfection process, we’ve developed an industry-first Individual post-filter solution. For this, we install a UV - our unique Wafer® UV system – on each individual filter outlet before the combined filter channel.
This enables a wider range of water treatment plants to adopt UV disinfection technology, but it also delivers key cost, environmental and operational benefits. These smaller UV systems can save between 40-50% of the costs of a usual system, when you take into account the installation expense and whole life costs. In addition, due to optimising the head loss with the Wafer system at the point of installation, this often mitigates the need for further pumping stations, which can reduce operational power costs by more than 20%. Furthermore, by utilising a UV at each filter, you increase system resilience. Each filter and UV works in tandem, so you don’t have to shut down the full filter system of a site to service or maintain the UV systems.
Innovation in action – Wafer® UV system*
This innovative approach has already delivered benefits for Northumbrian Water. It needed to improve reliability and resilience at its Mosswood works in County Durham by installing UV disinfection, Naturally, the outlet of the plant’s twelve rapid gravity filters was quite congested. Evoqua solved the challenge with the plan to install its Wafer UV system into the outlet of each of the twelve rapid gravity filters within the filter gallery. Each with its own independent monitoring of UVI intensity and UVT, this arrangement gives much more resilience than the more usual duty/assist/standby configuration.
Market research conducted by Northumbrian Water identified that the Wafer system was the only product on the market able to meet the project requirements from an installation and operations perspective. In addition, the Wafer system boasts a superior head loss which is critical for the individual post-filter approach.
Importantly, installing the UV systems in the existing filter gallery meant that there would be no need to break ground and build a new disinfection building. Northumbrian Water trialled the system at one of the filter outlets. The trial was so successful that it is now making significant investments to install similar units on the other eleven filters by the end of 2022.
Sitting at the heart of the success of any innovation in water treatment is collaboration. It’s through close collaboration between engineers and technology providers that innovative solutions can be identified and seemingly impossible challenges overcome. Our unique post-filter Wafer UV system is an excellent example of this. If there’s a challenge you need to overcome, there may be space, cost or time restrictions you face, then speak to the experts and work closely with your partners – I’m sure there will be a way round it.
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*Evoqua UV disinfection generator systems undergo third-party validation testing in accordance with the UVDGM (USEPA, 2006). Validated products are tested to confirm a minimum inactivation equivalent of 3 log (99.9%) for microorganisms in accordance with NSF/ANSI 50 and the UVDGM. Performance is not claimed nor implied for any product not yet validated; unvalidated products use single point summation calculations to provide delivered dose recommendations. Performance limitations depend on feed conditions, overall installed system design, and operation and maintenance processes; please refer to Operations Manuals. For more information: Contactus@evoqua.com