Water & Wastewater Treatment

In the know Digging deeper: UV disinfection 32 |OCTOBER 2015 | WWT | www.wwtonline.co.uk will usually be greater, however lamp ageing and fouling may have reduced output resulting in an undetermined dose. Using measured intensity allows the UV system to compensate, and any reduction in UV output to be identified and actioned. The issue that end users of UV systems must be aware of is that, although most manufacturers equip their UV systems with an intensity sensor, not all use delivered UV energy as a key parameter when reducing UV system power. Only when flow, UVT and intensity are properly measured, not assumed, can accurate real time dose be calculated and the system safely operated. It is entirely reasonable and proper that any UV system should be designed for worst case conditions. However, this means that for most of the time, the UV system will be oversized with a resulting excess use of power and consumables. The only safe and reliable way to reduce the system power is to utilise a dose equation that uses the real time values of flow, UVT and intensity and then to use the calculated dose to control system power. In this way, it is possible to minimise power consumption and lamp replacement, whilst ensuring that the primary objective of disinfection, namely public health, is still met. Ultimately, users of UV systems need to ask themselves whether their system is capable of calculating real time dose, and if not, whether their processes are really as efficient as they could be. • Three factors that determine accurate UV dosage ● Flow rate: This defines the residence time of the effluent in the system ● UV transmittance (UVT): This is dependent on water quality ● UV intensity: The amount of energy being delivered by the system 1 Bryggen Road, North Lynn Industrial Estate King's Lynn Norfolk PE30 2HZ UK T: +44-(0)1553-776202 • F: +44-(0)1553-776335 E: info@GurneyEnvironmental.com • W: GurneyEnvironmental.com Copyright©2015 Gurney Environmental Ltd. All rights reserved. WEARS Australia and ResMix are registered trademarks of WEARS. RAW WATER SUPPLY SOURCE MANAGEMENT Contact us for more information ResMix ™ Source Management ResMix™ provides significant downstream OPEX savings through top-down circulation in raw water storage reservoirs. Iron, manganese, nutrients, blue-green algae, taste and odour forming compounds have all been eliminated or controlled after installation of ResMix™, resulting in more efficient treatment at the Water Treatment Plant. Cost effective, simple to install and very low energy consumption. ResMix™ offers proactive Source Management for the first time.

• Cover