'Plug & Play' for mercury-free pulsed UV
LightStream Technologies Inc of the US unveiled its new pulsed UV disinfection machine - the LSi - at October’s Aquatech convention in Amsterdam.
Chlorine has been the most common method of disinfecting water since the early 20th century. In 1998, however, the US Environmental Protection Agency (EPA) found that chlorine produces by-products that pose risk for causing several forms of cancer as well as birth defects. Chlorine has been found to be ineffective in killing parasitic species such as cryptosporidium. In addition in the US, storage tanks for chlorine gas used in most treatment plants have also become a significant security concern in the wake of heightened terrorist threats.
Limitations & compromise
Until now, the most common alternative disinfection methods to chlorine have been ozone, membrane filtration, and mercury lamp UV light systems. Each method still requires significant compromises on both safety and performance. Ozone generators and containment equipment are difficult to maintain and susceptible to dangerous gas leaks; in membrane filtration there is risk of the membrane breaking or being damaged; and mercury lamp UV systems require the use of fragile mercury lamps to produce UV light - the United Nations recently concluded that there is sufficient evidence to take required action to reduce or eliminate the global use of mercury in products and industrial processes and cut mercury emissions.
LightStream’s LSi delivers powerful and precise disinfection without the dangers of chemicals, mercury lamps or ozone gas that risk the safety of workers, the public and the environment.
Key features include six Sigma quality control processes, brand name components and ISO 9002 certification. The LSi’s performance-based disinfection method is a departure from existing prediction-based systems, and enables water managers to achieve complete control and accountability for their UV disinfection systems by providing actual real-time measurement, control, and reporting capabilities.
Through its patented Constant Optimum Dose methodology, each unit conducts continuous sub-second analysis of both UV output and the water’s UV transmittance, and then intelligently performs instant adjustments to deliver the exactly specified UV dose. This is done by means of an internal closed loop control system which adjusts the reactor module’s UV power and/or flow rate to accommodate a wide range of varying influent conditions. The use of advanced pulsed UV dramatically enhances the safety of UV disinfection because it produces the UV by means of short, high-current pulses of electricity (up to 30 per second) through a harmless, inert xenon gas. Also, unlike with some mercury lamps that have to operate continuously at high quartz envelope pressures (several bar) and very high temperatures (600°C), the pulsed UV lamp is not pressurized and operates at a very low temperature, eliminating the potential for an explosive and catastrophic release of mercury into water streams.
LightStream’s use of pulsed UV significantly enhances the disinfection performance of ultraviolet light, said Chris Zanardi.
UV output efficiency (and subsequently the UV dose) is consistent, because the output is neither dependent upon the lamp operating temperature nor the associated temperature changes in the ambient cooling (influent) water; the short pulses and resulting low duty cycle of the pulsed UV lamp allows the exterior cooling jacket temperatures to be very close to that of the influent water, producing a UV source that doesn’t require mechanical cleaning attachments or chemical cleaning, scrubbing or maintenance.
The very nature of pulsed UV is ‘instant on’ and ‘instant off’, negating the need for system warm-up and temperature stabilization prior to operation; and the enormous peak power per pulse capability of the pulsed UV lamp (6,000,000 watts peak UV-C per pulse) delivers an order of magnitude greater UV photon flux density upon pathogens.
The LSi is a self-contained ‘plug and play’ machine with a full powered PC touch screen control panel available in 22 languages (including Help screens). A closed-vessel UV reactor that has been optimized through computational fluid dynamics safely houses a single non-fouling lamp that can be replaced as an enclosed cassette in minutes.
Integrity and efficiency
Because the LSi monitors lamp integrity and performance with each pulse, plant managers know in advance when to order and install a replacement. The LSi also provides instant digital reports on the system’s economic efficiency (both accumulated and real time), safety status, service history and service alerts.
The LSi is a complete disinfection solution that compares well with the total ‘turn-on’ capital costs of other less complete systems, and provides good value over its 15-year life cycle.
LightStream only sells its products in markets that are serviced by a LightStream Technology Provider with factory-trained technicians and in-stock spare parts. All LightStream products are fully supported by a comprehensive 24-month warranty and in-market technical service.
The LSi is easily scalable for various water and wastewater applications, whereby units can be easily linked together to accommodate a site’s particular flow-rate conditions, influent quality, and the desired effluent quality.
Each LSi can treat up to 160 m³/hr (1 MGD) and serves a wide range of applications that include industrial process fluids, municipal wastewater, potable water, cooling towers, VOC remediation, and municipal swimming pools.
The LSi is scheduled for shipment to EU countries in January 2003 that include the UK, Ireland, Spain, the Czech Rep, the Slovak Republic, Poland, France and Italy. Lightstream is planning to introduce further LS Series products will be introduced in 2003.