Technical Bulletin 148 Comparison of Flat Panel to MiniPanel by: Environmental Dynamics International Published: 6/2005
BULLETIN BRIEF Environmental Dynamics International offers a full spectrum of fine bubble aeration mixing platforms including the tube diffuser, the disc diffuser, and a MiniPanel type of diffuser unit. This EDI spectrum of diffuser types is valuable in allowing selection of optimum design and optimum performance characteristics for each project. In the industry flat panel type diffuserss have been generally recognized to offer a highh level of SOTE clean water performance and many times the systems are selected on the basis of that high SOTE alone. DISCLAIMER Technical Bulletins are presented as a service by Environmental Dynamics International headquartered in Columbia, Missouri USA. For additional more information regarding this particular bulletin or your specific aeration application contact Environmental Dynamics International by calling +1.573.474.9456, toll free at +1.877.EDI.AIR8 (877.334-2478), or via email at techbulletins@wastewater.com. 1 Technical Bulletin 148 Comparison of Flat Panel to MiniPanel
TECHNICAL BULLETIN 148 COMPARISON OF FLAT PANEL TO MINIPANEL Environmental Dynamics International is pleased to recognize the high efficiency of panel type diffuser systems. EDI also recognizes the full spectrum of characteristics associated with flat Panel type diffusers and has created the NanoPore TM and MicroPore TM Mini-Panel device as alternatives to the flat panel diffuser types. Use of the EDI MiniPanel device was developed to provide oxygen transfer efficiencies of flat panel configurations while producing actual energy savingss on a power evaluation basis because of significant reductions in operating pressure requirements. On any performance based evaluation of diffusers it is necessary to have a close evaluation of the total system cost of ownership. The initial phases of that evaluation includes an evaluation of the SOTE which is a prime driver in energy savings, and the diffuser operating pressure which is the second most important factor in long term energy savings. A comparison of the flat panel type of diffuser shows that their benefits are created as follows: Very high floor coverage by the diffusers to prevent directional hydraulic pumpages in the aeration basin and allow a freee rise of small gas bubbles in the mixed liquor contents. These floor coverages typically run between 20 and 60% floor coverage by membranes in order to generate high SOTE values. With high membrane floor coverage it means that there is a substantial active area of membrane in the basin. Air flux rates across this membrane are controlled to approximately 0.5 scfm/ft 2 or (8.5 Nm 3 /m 2 ) in order to avoid any coalescence of gas bubbles and in order to avoid the hydraulic pumpages taking the gas bubble to the surface at a velocity greater than the natural rise rate of the bubble. These operating characteristicscs are critical in order to assure maximum performance of the flat panel type product or competitive projects. Environmental Dynamics International recognizes the benefits outlined above for the flat panel devices. By developing the advanced technology MiniPanel device EDI has generated many benefits and advantages versus the flat panel type devices as outlined and described below: 2 Technical Bulletin 148 Comparison of Flat Panel to MiniPanel
1. Total energy value The EDI MiniPanel is able to deliver significant total energy benefits because it is able to deliver similar oxygen transfer efficiencies of flat panels with an operating pressure that is approximately 0.7 to 1.5 psi (4.85 to 10.4 kpa) less than the operating pressure of flat panel devices! The EDI Advanced Technology design recognizes discrete MiniPanel configurations minimize the pressure losses required to distribute air in the piping network and across the surface of the diffuser membrane. EDI MiniPanel units are approximately 0.236 m 2 of active surface area in a configuration of approximately 120 millimeters in diameter x 1400 millimeters long perforated top surface only, i.e. panel configuration. Having discrete MiniPanel modules allow air distribution in the system without high pressure losses. With an operating pressure savings versus flat panels that amounts to as much as 15 to 20% of the total operating pressure in the system. MiniPanel Systems deliver lower total energy cost in all applications. 2. EDI MiniPanel units are mounted on standard air piping/ air distribution systems which help control the operating pressure in the system. Air pipe sizes are chosen to deliver minimum pressure loss for the operation of the system and are not fixed to a size limitation of the flat panel type of devices. 3. Operational stress is a critical item in any aeration membrane. Flat panel type devices have a major problem with operational stress that has to be overcome and managed. The flat panel is vulnerable to high internal stress, high stress at any retainers or edges, and is limited in its application procedure accordingly. By comparison the EDI MiniPanel is designed as a tubular device in order to take full advantage of low internal hoop stress. These reduced operating stresses on the EDI systems are particularly significant in assuring long life and allowing operational benefits. See EDI Technical Bulletin 138. 4. Flat Panels claim beneficial geometry because membrane surface is supposedly flat during operation with uniform pressure across the entire surface. From Technical Bulletin 138, Figures 3,7, and 8 show flat panels when air is on. This is a comparison of the flat panels versus the MiniPanel devices shown in Figures 1a and 1b: a. Flat panels are flat when not in operation. b. Flat panels under air loading, i.e., in operation deflect upwards. 3 Technical Bulletin 148 Comparison of Flat Panel to MiniPanel
c. Flat panels deflection creates a similar shape segment in the total diffuser as an EDI MiniPanel. d. Discrete MiniPanel segments can be controlled for air distribution. e. Deflection of Flat Panels demonstrates effects of stress while the MiniPanels maintain their original shape with little deflection because of low Hoop Stress. 5. The active surface area of a membrane diffuser system is critical in the overall system performance. Drawing 42080, enclosed, shows how the MiniPanel can create very high floor coverage and distribution of energy in a basin while operating with discrete MiniPanels that can be installed, operated, and maintained very effectively. 6. With flat panels, routine flexing and increased flux rates rates are generated in order to try and prevent excess solids from accumulating and settling on the surface of the membrane. On/off operations create a particularly vulnerable situation for large panels resting against the floor. By comparison, the EDI MiniPanel is mounted 0.2 to 0.5 meters above the floor. The MiniPanel has a curved surface that is easily capable of shedding solids and the MiniPanels have discrete spacing between the individual units in order to allow the solids to pass by the diffusers when air is turned off. This prevents the accumulation of heavy solids and/or operational issues of fouling and clogging of the MiniPanel; no flexing required. 7. For mixing activities, the MiniPanels geometry allows localized MLSS pumpage and sweeps solids from the floor below and between units maintaining solids in suspension. The solids do not accumulate under or around or between the MiniPanel devices. 8. Heat resistance Flat panel membranes are typically constructed as materials that offer specific warnings against use in high heat applications. This high heat can be from deep tank operation requiring cooling of the air ahead of the diffuser system or in hot process applications. Limitations of these devices are documented in the manufacturer s literature and become a limiting factor in many applications; particularly because of the high stress effects on warm membrane materials. By comparison the EDI MiniPanel device offers a wide selection of membrane types with heat resistance, special chemical resistant polymers, coated membranes all with low Hoop Stress service conditions. A full list of membrane material is available for the MiniPanel device and allows its application in more difficult or severe operating conditions. 4 Technical Bulletin 148 Comparison of Flat Panel to MiniPanel
9. Air flow ranges The flat panel type devices are limited to low air flow rates in order to get proper distribution and utilization of the surface of the membrane. Typically the air flow rate for panels is 0.50 scfm/ft 2 (8.5 Nm 3 /m 2 ) to maintain efficiency and control pressure losses. By comparison the use of discrete MiniPanel type devices can be controlled with individual orifices for total piping air distribution and the air distributed over the surface of the membrane with an engineered opening in the membrane itself. Openings can be engineered for 0.5 to 2 mm in length in order to provide an engineered range of operating air flows at reasonable pressure loss. Air flow rates can be engineered per MiniPanel to operate effectively at 0 to 10 scfm/ft 2 (0 to 170 Nm 3 /m 2 ) flux rates. This can be extremely important and critical in high rate or high oxygen uptake systems where space may be limited and very high energy levels are required in the reactor. 10. EDI membranes are modest in size and are designed to allow changing in less than two minutes per membrane. By comparison the flat panel type of devices are generally quite large and have a tremendous number of bolts and connections necessary, trying to hold the membrane in its proper location because of the high stresses as outline above. Time to replace the units or membranes is low for an EDI system compared to the flat panel devices. 11. The cost of EDI replacement membranes is dramatically less than the cost for the flat panel type of device. This can be particularly beneficial if there is damage to a membrane. It is easy to change one small EDI MiniPanel membrane in a couple of minutes compared to replacing a large membrane that can require as much as 8 to 10 hours by multiple personnel for proper replacement of flat panel units. The capital cost of the EDI membrane is also modest by comparison. It should be noted that some flat panel type of devices have determined that it is so hard to protect them from high stress or is so difficult to change membranes that they have made membranes permanent as a throw away type of units; again creating major economic loss for maintenance of these systems. 12. EDI MiniPanel units are designed to allow easy application of retrievable diffuser systems. Retrievable diffuser systems can be advantageous in difficult applications and the MiniPanel is well suited to an engineered retrievable solution. By comparison the flat panel types of devices are typically fixed to the floor and are almost impossible to create a retrievable diffuser system arrangement. 5 Technical Bulletin 148 Comparison of Flat Panel to MiniPanel
13. Using the EDI MiniPanel device allows access to the basin for cleaning and/or maintenance by walking between rows of diffuser units and working between those diffuser assemblies. By comparison a high floor coverage of flat panels prevents access for inspection, maintenance and/or any mechanical activity in the basin. 14. EDI MiniPanel units can be mounted on any type of a pipe, plastic or metal. These choices of materials are an engineering benefit for use by the engineer or owner. By comparison, flat panel type of devices are limited to feeding with flexible hose connections in most applications or are limited to one type of piping for the installation. 15. Conversions of existing aeration systems to high density MicroPore or NanoPore MiniPanel units for energy savings can be done and generally maintain the existing blowers. Flat Panels operating pressures because units are on the floor and because of excessive pressure loss across the membrane require new high pressure blowers. In summary, the EDI MiniPanel Advanced Technology diffuser system offer substantial benefits in a total cost of ownership versus flat panel devices. The MiniPanel can deliver similar oxygen transfer efficiencies, dramatically lower operating pressures and deliver a net savings in operating energy cost! In any evaluation it is necessary to balance the operating pressures and the the oxygen transfer capabilities and EDI allows the design engineer full flexibility in the application of those basic engineering principles. For operation maintenance and overall system flexibility, the MiniPanel system has a dramatic number of benefits that should be incorporated in those systems where high operating efficiency is desired for low total cost of ownership from a consideration of capital cost, operating cost for energy, plus operation and maintenance costs as a net present value (NPV) or net present worth (NPW) evaluation. Reference Figure 1 on Next Page. 6 Technical Bulletin 148 Comparison of Flat Panel to MiniPanel
Figure 1 7 Technical Bulletin 148 Comparison of Flat Panel to MiniPanel