DEVELOPMENT OF AN INCLINED ORIENTATION UV SYSTEM PERMITS SMALLER FOOTPRINTS. Kevin Flis Wedeco, A Xylem Brand

Transcription

1 DEVELOPMENT OF AN INCLINED ORIENTATION UV SYSTEM PERMITS SMALLER FOOTPRINTS Kevin Flis Wedeco, A Xylem Brand Please address correspondence to: Phone: (704) or kevin.flis@xyleminc.com ABSTRACT The two most popular requests generated from facilities required to disinfect is to have a Ultraviolet (UV) system that produces more power in terms of UV output and to minimize the footprint. By recognizing the need for a compact, efficient, and potent disinfection system and learning from the existing treatment solutions available, the inclined orientation system was developed. Traditional UV systems require long channels to accommodate the entirety of the lamp length and were not efficient with their use of space (having a large space between banks). While UV systems utilizing vertical lamps have a reduced channel length, the depth of the channel significantly increases compromising ease of installation and maintenance. To remedy these issues an inclined UV disinfection system was developed that maximizes all the space used to disinfect. The inclined system uses a 45 angle to maximize the disinfection time in the channel, minimize the depth of the channel, and provide maintenance accessibility. Central to the tight footprint layout is the ability for the inclined UV modules to actually overlap one another in series. The 45 angle design minimizes the distance between modules (~4 feet) and produces a tight disinfection zone with no wasted space. Furthermore, the inclined design reduces the depth of the channel versus vertical systems by as much as 37%. Couple this design with the development of a more potent, yet energy efficient, lamp and you have a UV disinfection system that is capable of treating flows within a very compact footprint. The newly developed low-pressure, high-output (LPHO) lamp operates at a power of 600 W. The new lamp was able to accommodate the 600 W, maintain power economies of the entire system, and maintain the same arc length as the traditional horizontal lamps. The inclined system can treat the same flow with as little as 50% fewer total lamps when compared to traditional UV systems. Since the UV module head is strategically placed at the top of the channel, it provides the operations staff an easy way to access equipment above water. With the inclusion of an automating lifting mechanism that is integral to each UV module, below water equipment can easily be accessed as well. Maximum residence time, a 37% reduction in channel depth, and lamp output that is double its predecessor are all unique features that make UV disinfection economical for large treatment systems with the inclined orientation design. This design method has been implemented and the first treatment systems expected to receive flow in the Carolinas will occur in Fall KEYWORDS Ultraviolet (UV) Light, Open Channel, Closed Vessel, UV Banks, Staggered Array, Computational Fluid Dynamics (CFD), Validation Testing, UV Dose, Ultraviolet Transmittance (UVT), UV Sensitivity, National

2 Water Research Institute (NWRI), International Ultraviolet Association (IUVA), United States Environmental Protection Agency (US EPA) INTRODUCTION Ultraviolet (UV) light has found to be effective in disinfecting bacteria such as E.Coli and Fecal Coliforms. The mechanism for disinfecting the E.Coli and Fecal Coliforms is that the UV light actually irradiates the DNA structure of the bacteria by producing dimers between the thymine bases. The result is the affected enzymes no longer function and the microorganism is no longer able reproduce or die off. To determine how space can be used efficiently, we must first explore the delivery and pathway of the UV light into the wastewater stream. One of the more common practices of delivering this UV light is in an open channel. An open channel is created by using a concrete or stainless steel channel on three (3) sides with an open surface on the top. Open channel configurations are frequently used in gravity flow situations due to their improved accessibility of equipment as compared to closed vessel reactors (in pipe UV systems). Open channel systems deliver their UV light by creating an array of UV lamps that are either parallel with the path of flow, which is generally discussed as a horizontal configuration and seen in Figure 1, or perpendicular to the path of the flow, which is generally discussed as a vertical configuration and seen in Figure 2. Figure 1: TAK 55 Horizontal Lamp Arrangement as manufactured by Wedeco.

3 Figure 2: Aquaray 3X Vertical Lamp Arrangement as manufactured by Ozonia. Facilities seeking to use UV to disinfect flow rates greater than 5 MGD often run into footprint constraints when evaluating the size of horizontal and vertical open channel configurations. This is attributed to the large quantity of lamps required to achieve the disinfection. For this reason, the arrangement of the UV lamp array is critical, because it directly impacts the UV system footprint. Specifically, horizontal lamp arrangements require a large space between UV banks (a cluster of lamp arrays arranged in a set) as seen in Figure 3. Vertical lamp arrangements require very deep channels (up to a 10 depth in certain cases), which can drive up installation cost for excavation and excessive concrete. In an effort to achieve a reduced system size, a different orientation that creates a more efficient use of space will be evaluated. Figure 3: Two (2) Horizontal Lamp UV Banks with Space Between Banks The UV light delivery is not only a function of the arrangement of the lamp array, but also the potency of the UV lamp itself. Another way to reduce the size of the UV systems is to improve the potency of the lamp without compromising the efficiency and size of the UV lamp, which can create difficulty on Owners to operate and maintain. A more potent lamp will also be evaluated.

4 METHODOLOGY The lamp orientation evaluated was the inclined type. The inclined orientation was first introduced in drinking water over 15 years ago. The diamond shaped closed vessel K Reactor as manufactured by Wedeco uses lamps at a 45 degree angle (as can be seen in Figure 4) to the path of the flow. Additionally, the lamps are oriented in a staggered array (as can be seen in Figure 5), which actually places the lamps in subsequent rows in the gaps of the lamps from the previous row. Figure 4: K Reactor Inclined Lamp Orientations as manufactured by Wedeco The closed vessel K reactor has improved hydraulics and superior throughput to any other closed vessel system available. Therefore using this same 45 degree angle concept for wastewater open channel systems was evaluated to see what footprint and throughput advantages could be achieved. The first step in evaluating this lamp orientation for wastewater open channel systems is to perform Computational Fluid Dynamics (CFD). The CFD analysis shows what the hydraulics of the unit would achieve and how the UV light array would penetrate the wastewater to achieve the necessary disinfection. An example of this CFD analysis is shown in Figure 5. Figure 5: Example of CFD Analysis for Inclined Lamp and Staggered Array Configurations. After the CFD proves successful, the second step is to manufacture units in order to perform a validation test. The validation test places the UV system into several different scenarios to see the resulting UV

5 disinfection, UV dose (a measured level of UV light multiplied by the time the UV light was in contact with the wastewater), and throughput. The data from this test is used to determine how all systems will be scales for different flow rates. Traditionally, a small scale or pilot version of the equipment is used in the validation testing, but to ensure the equipment met the highest of standards a full-scale (up to 16 MGD) inclined orientation system was manufactured for the validation test site. The test site consisted of four (4) 12-lamp UV banks placed in series as can be seen in Figure 6. Actual wastewater was run through the validation equipment and a wide range of flows, UV doses (up to 100 mj/cm 2 ), and Ultraviolet Transmittances (UVT) (down to as low as 20% UVT) were tested. The test was performed by Carollo Engineers. Figure 6: Duron as manufactured by Wedeco Validation Test Site with Four (4) Banks in Series The tests use a biological surrogate that react the same way to UV light as the critical bacteria (E.Coli, Fecal Coliform), but do not have the harmful impacts that the critical bacteria have. The way that a biological organism reacts to the UV light is labeled as the UV sensitivity (this is typically represented as mj/cm 2 of UV dose required per log inactivation of the organism in question) and is explained in more detail in Figure 9 of the Results section. In parallel with the new reactor design, a new lamp was being evaluated to determine how the lamp power could be increased while also maintaining a high energy efficiency and short lamp length for easy use and handling. Many different lamp outputs were evaluated as well as different lamp lengths, while constantly considering lamp efficiency to determine the best lamp for this arrangement. Ideally, a high output lamp would be achieved, with a high energy efficiency, and shortest possible lamp length to achieve the former two (2). RESULTS The CFD analysis of the 45 degree inclined orientation design showed superior disinfection results via the pathway developed by this system. This was ultimately measured by how much flow could be processed with as few lamps as possible and within a compact footprint. However, these results will be discussed later in the paper as a combination of both the inclined orientation and the improved lamp contributed to this success.

6 Regarding the CFD analysis, it did show another superior benefit of the inclined design. The analysis showed by inclining the systems at a 45 degree angle, the units could actually overlap one another in series, eliminating the wasted space in between UV banks that is common with traditional UV systems. The way the equipment is arranged actually places the previous module s bottom lamp location at the same cross section as the subsequent module s top lamp location (see Figure 7). This means that the wastewater is being contacted by UV light for its entire path through the UV channel and that there is an efficient use of the space being utilized by the UV banks. Figure 7: Graphic displaying the Duron UV banks in series, which employs an efficient use of space. The original concern was that by using this stacking method, accessibility of the equipment below the water level would be difficult. However, this was compensated for by including an integral lifting device on each UV module to lift up out of the channel on the 45 degree plane that it is arranged. Figure 9: The inclined orientation of the Duron modules in the lifted position, which is inclusive to a single plane per UV module. Secondly, the inclined plane allows the channels to be much shallower than traditional vertical UV systems. Channel depths with the inclined orientation design are only 6-3 deep, which is >37% shallower than the most recent vertical UV designs on the market (10 deep).

7 The next step was to have Carollo perform the validation test. Multiple surrogates were used during the validation test, including MS-2 and T1, to determine the effectiveness of the inclined orientation system for both wastewater and wastewater reuse applications. More importantly, a multiple surrogate approach allows you to test how the UV system handles organisms of different UV sensitivities and allows the designer to use a site specific sensitivity for future projects. This is called the D L approach. For example, Figure 9 below shows that the T1 surrogate closely resembles E.Coli and Fecal Coliform. For this reason it would be wise for the designer to select it as the appropriate surrogate for installations that require those permit limitations. But since the MS-2 and T1 surrogates have vastly different UV sensitivities, by creating an envelope between both surrogates a wide range of sensitivities are covered (not just E.Coli and Fecal Coliform). This D L approach gives the best fit by allowing the system to be designed to any target organism with any water quality. Figure 9: Graph of multiple surrogates and the UV Doses required to get specific log inactivations. By using the D L approach, the inclined orientation system succeeded in completing the validation test for the National Water Research Institute (NWRI), International Ultraviolet Association (IUVA), and United States Environmental Protection Agency (US EPA) protocols. This allows the equipment to be designed for all applications and for all different water qualities. Regarding the lamp itself, many different scenarios were tried, but the best result occurred at a lamp power of 600 W. The 600 W lamp created the right amount of UV intensity to penetrate the wastewater stream and generate the appropriate UV pathway for disinfection. At 600 W the lamp was capable of maintaining a quality individual lamp efficiency and short lamp length. This has been labeled as the sweet spot. The sweet spot is shown in Figure 10 with a lamp power of 600 W and a lamp length of only 4-8 along with a quality lamp efficiency. The 600 W lamp has significantly reduced the number of components required to treat medium to high disinfection flows and coupled with the inclined orientation has decreased the footprint of UV installations.

8 Figure 10: Showing sweet spot of lamp output, efficiency, and arc length for the inclined orientation system. DISCUSSION The overall impact that the inclined orientation system has is by reducing the overall number of components (lamps, cabinets, etc ) required to treat medium to high disinfection flows, reducing the energy requirement to treat these flows, and by reducing the footprint of the equipment that is required to treat these flows. The bar graph in Figure 11 shows that the inclined orientation system using the Duron as manufactured by Wedeco, lamp count and power requirement both were reduced when compared to traditional UV systems. In fact, the inclined system reduced the lamp count by nearly 54% and the power requirement by nearly 5% at the very first inclined orientation Duron system installed at Camden, SC. These values are modest in comparison to other results that are being recognized at other facilities. In fact, a study was performed at a Midwestern installation that resulted in a lamp count reduction of 75% and an energy reduction of nearly 48% with the inclined orientation system.

9 Figure 11: Comparison of horizontal to inclined lamp counts and power consumption. These lamp count reductions also lead to significant reduction in the amount of other components needed to operate the lamps, including the cabinetry that houses the electrical equipment. At the Camden, SC inclined orientation Duron installation, a reduction of six (6) cabinets (9 down to 3) was realized by the its utilization. This compact design has led to a renewed interest in using UV disinfection for medium to high flow facilities, because of its improved footprint and manageability. CONCLUSION The inclined orientation system presents a unique option to facilities evaluating disinfection for medium to high flow scenarios (>5 MGD peak flows). The compact design that utilizes no wasted space between banks makes the most of the space that is used and the inclined design reduces the depth of the channel by >37% compared to the most recent vertical UV systems. The sweet spot lamp technology reduces traditional UV lamp counts by at least 50% making UV disinfection feasible for larger flow facilities that would traditionally rule it out just based on the scale of the lamp count alone. Additionally, the lower lamp counts reduce the other major equipment required for a UV system to provide an overall superior level of manageability. The one major obstacle that was limiting the stacked design of the UV banks for the inclined orientation was accessibility to equipment below the water level. However, with the integral lifting device, this limitation was not only overcome but provides even superior accessibility to the equipment below the water line when compared to traditional UV systems.

10 All of these benefits combine to create a system that is more economical and more manageable for medium to large flow facilities to use UV light disinfection system by harnessing the design of the inclined orientation unit. A total of six (6) inclined orientation installations exist with the first in Camden, SC to begin disinfecting wastewater by Fall ACKNOLWEDGEMENTS Special thanks to Carollo Engineers for their work in the validation of the Duron unit. Our expression of gratitude to the Camden WWTP and URS for their combined efforts in the installation of the first Duron unit at Camden, SC. REFERENCES Andriamriado, Laurent; Asensi, Daniel; Baig, Sylvie; Ballard, Temple; etc Water Treatment Handbook 7 th Edition 2007 Salveson, Andy; Fontaine, Nicola; Xylem Water Solutions Wedeco Duron UV System Validation Report April 2013