Since the 1950s, lamp manufacturers have tweaked lamp technology to enable the production of more UV light output. As a result, low pressure high output, medium pressure and amalgam lamps were introduced from the 1950s to the 1990s. In the late 1990s, a revolutionary change in UV lamp technology was released through the commercialisation of microwave UV lamps into water and wastewater UV disinfection systems.

Microwave powered UV lamps represent a significant advancement in UV lamp technology since they are electrodeless and remove the major failure mechanism found in traditional UV lamp technology. Traditional UV lamps fail by one of two means, electrode breakage and fade. By not having an electrode, microwave lamps do not suffer from the first failure method. The second type of failure, lamp fade, is also solved by removing the electrode. When a traditional lamp fades, the electrode wears out producing a grey / brown staining at the ends of the lamp. This can often be seen on florescent lamps, which are very similar to UV lamps. As the electrode wears, the actual brightness of the lamp diminishes over time, requiring traditional UV lamps to be replaced about every year.

Microwave UV lamps are powered by microwaves which excite the mercury-argon gas mix in the lamp to produce UV light. Commercial microwave UV disinfection systems for water and wastewater treatment are available from Severn Trent Services.

Severn Trent Services offers two types of MicroDynamics® microwave UV systems; an open channel for use in waste water plants, and closed vessel for use in drinking water, waste water, and industrial applications. Advantages of MicroDynamics include increased safety; reduced operational costs; consistent disinfection; flow pacing; and lower whole life costs.

The fill inside the MicroDynamics microwave UV lamps is very similar to traditional UV lamps, which means they produce the same 254 nm light generated by traditional low pressure high output lamps. MicroDynamics lamps feature an electrodeless design. Without an electrode to wear out, the lamps produce even, fade-free UV light over their entire life.

Unlike traditional lamps which limit starts and stops to four times a day, MicroDynamics microwave UV lamps have no cycle limit. Traditional lamp electrodes wear out due to successive heating and cooling. Without an electrode, MicroDynamics lamps can be turned on and off as often as needed. Additionally, MicroDynamics lamps start up in about a minute, compared to the five to ten minutes it takes traditional lamps to start up. This means less chance of producing non-treated water after a power failure and restart.

The MicroDynamics microwave UV lamps are enclosed in a wave guide, which keeps the microwaves in, while allowing UV light to emerge. This feature is analogous to the mesh seen in kitchen microwaves, which does the same thing. There is no electrical connection between the power head and the lamps. This makes maintenance much easier and safer with our system when compared to traditional systems that have wiring harnesses that must be individually removed.

The MicroDynamics microwave UV lamps are offered with a three year lamp warranty.

The MicroDynamics systems feature a chemical free wiper. Unlike other UV systems in which lamps run over 200 degrees F (93 degrees C), MicroDynamics sleeves are kept at 115 degrees F (46 degrees C), which means they are less susceptible to baking on foulants. And while some traditional systems introduce an acid cleaner into their wipers, in an attempt to make their wipers clean better, the MicroDynamics system does not need that extra complication, since the sleeves are kept cool.

In wastewater applications, the MicroPace™ flow pace technology is used with MicroDynamics systems to match UV dose to operating conditions in real time, resulting in energy savings and efficient system use. MicroPace enables the lamps to be turned down or off so the system maintains a constant dose and is only using the power needed to disinfect and meet site specific needs, ensuring the most efficient and effective use of the system design.

The secondary benefit of MicroPace is a conservation of energy which reduces costs. MicroDynamics electrodeless lamps can re-strike immediately in the event of a power outage since they do not require a cool down period. One major benefit arising from this aspect is that there is no requirement for standby power or UPS systems, leading to significant capital cost savings.

MicroDynamics wastewater systems can operate in a dry or partially-filled channel. The systems employ an automatic, chemical-free cleaning system. Further, their vertical configuration and increased reliability of the systems reduces stand-by requirements to less than 25 per cent.