Open channels are an effective and efficient method of moving water in large scale treatment applications without the need for costly piping or pumps. The Purgo EnviroTech, (PET), Cloacina™ Open Channel UV Treatment Systems are designed for applications where the fluid being treated is flowing in an open channel under the force of gravity.
The Case for the Vertical UV Rack
The Cloacina™ Open Channel UV Treatment System consists of a stainless steel framework, referred to as a "UV Rack", that supports the UV lamps, vertically, in an open channel. The UV Racks are available in a 12-lamp, 400mm wide (16") configuration or a 24-lamp, 600mm wide (24") configuration.
The vertical UV Rack drastically reduces the installations' footprint and infrastructure requirement when compared to horizontal UV treatment equipment. Our UV racks are a natural fit into typical existing chlorine contact chambers of wastewater treatment facilities. Once installed, the vertical UV Rack seldom requires removal since all the lamps and quartz sleeves are accessible from the top of the rack, above the waterline.
The UV Fluence is enhanced by the superior mixing created by the perpendicular water flow in a vertical UV Rack as compared to the parallel flow in horizontal rack installations. In addition, the UV lamps are arranged in a staggered array to further improve mixing. Consequently, the failure of a lamp in a vertical system is far less detrimental to the average UV Fluence as compared to a horizontal rack where the water will tend to flow in a laminar fashion along the length of the defective lamp.
All the UV lamp electrical connections of the Cloacina™ system are made safely inside quartz sleeves, above the water line, while horizontal systems are problematic due to the submerged connections.
UV Rack Hydraulic Design
The hydraulic design of the UV Rack and UV lamp placement play a significant role in the efficacy of the UV Treatment process. Our designs incorporate a staggered lamp configuration that promote the uniformity of the ultraviolet intensity field. Strategically located flow disrupters enhance the mixing of the fluid to further increase the average UV Fluence (or dosage). Analysis of the hydraulic behavior of water within the UV Rack using Computational Fluid Dynamics, or CFD, assisted our engineers in designing hydraulically efficient systems with minimal pressure drop and optimized flow velocities throughout the UV Rack.
UV Rack Construction
The entire UV Rack is manufactured from highly corrosion resistant Type 316L Stainless Steel. Type 316L is superior to Stainless Steel Type 304 in strength and crevice corrosion and pitting resistance. All of the stainless steel components are welded by the TIG or MIG technique, as appropriate. The completed UV Rack is Electrpolished to provide a superior corrosion resistant finish. All O-rings are FDA compliant Viton®. (Viton is a DuPont Dow Elastomers L.L.C. Trademark).
Open Channel UV Performance
The Cloacina™ Open Channel UV Rack can treat flows ranging from 150 m3/hour to 350m3/hr (660 USGPM to 1,500 USGPM), depending on the water quality and required UV Fluence Rate (or dosage), with minimal head loss. Similarly, UV Fluence Rates range from 30 to 300 millijoules per square centimeter (30,000 to 300,000 µW-s/cm2), depending on the flow rate and water quality. Any residual ozone will also be quenched, thereby protecting the downstream equipment and users or the environment.
Amalgam UV Lamp Technology
The Cloacina™ Open Channel UV Treatment Systems employ amalgam lamp technology exclusively. Our high performance UV-Xtender™ lamps produce over 400% more 254nm UVC output than conventional low pressure UV lamps while maintaining superior lamp efficiency.
Amalgam lamps have several advantages over medium pressure UV lamps. Any interruption of water flow in a medium pressure UV system can lead to drastic overheating because medium pressure lamps operate at up to 900°C while amalgam operate at only 100°C. Quartz sleeve fouling is more prevalent in medium pressure systems due to the higher UV density and lamp temperature. Therefore, more frequent sleeve cleaning is required. A lamp failure in an amalgam, multilamp system is much less significant as compared to a medium pressure system where a single lamp failure can reduce the UV Fluence level by 50% in a two lamp unit. The UVC efficiency of medium pressure lamps is typically only 15% while our UV-Xtender™ amalgam lamps provide an efficiency of at least 35%. The UVC radiation field density of our amalgam lamp Systems is more uniform than medium pressure systems due to the higher number of lamps presented to the water flow. Considering all these factors, the overall system efficacy of PET's amalgam lamp systems is far superior to that of medium pressure.
When comparing standard low-pressure lamp UV equipment performance with our UV-Xtender™ amalgam lamp equipment, one quickly realizes that there is a 400% reduction in the number of lamps, sleeves and associated hardware, both electrical and mechanical. This represents a significant reduction in the amount of equipment required to attain a specific level of treatment. Consequently, shipping costs, installation footprint and labour, infrastructure and head loss are reduced dramatically. This also correlates with a four fold reduction in maintenance time and labour associated with sleeve cleaning, lamp replacement and general servicing.
The operating life of our UV-Xtender™ lamps is up to 16,000 hours, depending on factors such as lamp operating conditions, number of daily on/off cycles and the duration of the off period. Our amalgam lamp life is 3 to 4 times that of typical medium pressure lamps. Our confidence in our UV-Xtender™ amalgam lamps is shown by our willingness to provide a 12,000 hours lamp life Warranty, subject to certain terms and conditions that are presented in the PET Warranty. For complete Warranty details, please e-mail the Purgo EnviroTech head office.
Electrical efficiency of the entire UV Treatment System has become a major concern in these days of high energy costs. Our high efficiency, Hi-E™ electronic ballasts boast a 94% nominal efficiency rating when used in conjunction with our UV-Xtender™ lamps. Our Hi-E™ electronic ballasts provide a constant drive level, despite variations in the AC line voltage. This maintains a stable UVC output from the lamps and maximizes lamp life. In addition, our ballasts are powered up sequentially to dramatically reduce the UV Systems start-up surge current. This virtually eliminates nuisance circuit breaker tripping.
Electrical Control System
|A Programmable Logic Controller or PLC is incorporated into all our UV Treatment systems. It controls and monitors the operating status of the UV System and displays relevant parameters on a local backlit LCD display. In the event of a fault, the location of the fault is also shown on the display and the operator is alerted to the fault condition through visual indicators, an alarm relay operation, or optionally through a remote Operator Terminal via an RS-485 multidrop communications link. The PLC monitors the operating status of each UV lamp and watches for an over-temperature condition associated with the electrical equipment. The temperature monitoring is very useful in preventing damage to the electrical equipment in the event of a high ambient temperature condition.|
|Filtered forced air cooling is provided to maximize the operating life of all the electrical components. Air conditioning is available as an option for when the installation environment is greater than 40°C. Mean time between failure (MTBF) data for MOSFET semiconductor devices show that "every 10°C reduction in junction temperature delivers a twofold increase in MTBF." (Jason Zhang of International Rectifier; "Advanced Packaging Boosts Power Mosfet Performance"; Power Systems Design - Europe, March 2004). The industry standard electrical enclosure that houses the electronic ballasting and all control and interface circuitry is rated at Nema 12 (IP55) with Nema 4X (IP66) as an option. (Ref. Hoffman Enclosures)|
The optional Purgo EnviroTech Model SUVO Sensor measures the relative UVC intensity of the germicidal 254nm wavelength within the UV Rack. The output from the UV sensor is processed by the PLC and the resultant, relative intensity is shown on an LCD display in %. This level is compared to set points established within the PLC to determine if the relative UVC has fallen to the minimum level required for proper treatment or is approaching the minimum level. Appropriate visual alarm indicators are activated by the PLC to inform the operator of the respective condition. This feature enables the operator to note when water quality has degraded or the UV lamps are approaching their end of useful life.
The semiconductor device that is used to detect the 254nm UVC is of a highly advanced composition that exhibits minimal UVC degradation over time. This helps to ensure the long term accuracy of the SUVO Sensor.
A more accurate representation of the average UVC field intensity within the UV Rack can be acquired by incorporating multiple, strategically positioned, SUVO Sensors within the multilamp arrangement of the UV Rack. This increases the effective UVC sensing area and provides a more accurate representation of the average UVC field intensity.
Maintenance of the UV System
Maintenance of the Cloacina™ Open Channel UV System includes periodic cleaning of the quartz sleeves and the electrical enclosure cooling fan filter(s), as well as scheduled lamp replacement. The UV lamps can be accessed in less than two seconds with our proprietary 316 stainless steel Rapid-X™ bayonet style fittings.
The design of the Rapid-X™ fitting is such that the entire assembly is virtually waterproof. An O-ring, integral to the male bayonet fitting, prevents splashed water from entering the quartz sleeve and breaking or shorting out the operating lamp. An additional seal, within the knurled compression nut, prevents splashed water from entering via the lamp cable or threads of the compression nut.
Depending on the application and water quality, periodic quartz sleeve cleaning can be accomplished with an optional manually operated sleeve cleaner, or alternatively, with an optional automated cleaning system that is programmed to clean the quartz sleeves at a frequency set by the operator.