Technical Bulletin 166. Partial Mix Lagoon. Retrievable. Environmental Dynamics Dyna. by:

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1 Technical Bulletin 166 Retrievable Partial Mix Lagoon Diff ser Design Aeration by: Environmental Dynamics Dyna International s Published: 2/2018

2 BULLETIN BRIEF Proper Oxygenation and Mixing for Maximum Performance is achieved using many of the following design guidelines. Reference drawing Partial Mix Lagoon attached. DISCLAIMER Environmental Dynamics International, headquartered in Columbia, Missouri, USA, presents these Technical Bulletins as a service to our customers. For more information regarding this bulletin or your specific aeration application, contact Environmental Dynamics International at +1 (573) Technical Bulletin 123 Retrievable Diffuser Aeration Systems Copyright Environmental Dynamics International 2017 All Rights Reserved

3 TECHNICAL BULLETIN 166 PARTIAL MIX LAGOON DESIGN 12 I. Inlet Zone Plan for extra energy for aeration and mixing near lagoon inlet: A. Accommodate immediate O2 demand from inlet waste. B. Distribute waste and inlet solids over a significant zone of the lagoon to minimize buildup of islands of sludge and inorganic solids at inlet. II. Use high efficiency aeration units such as EDI FlexAir diffusers: A. Tube assemblies. B. Panel assemblies. C. Disc assemblies. III. Recognize unit pumpage is significant with zones of influence of considerable size, but somewhat dependent on size of units or energy at each unit. Typical units show measurable water pumpage velocities in excess of 200 ft Ø. Circulation covers greater area, but not easily measured except for uniform DO. IV. Mixing to emphasize zones of aeration and mixing. Lagoons are typically plug flow designs and require means to distribute aeration and mixing side to side. Best results with zones or bands of aeration across the lagoon with diffuser units in rows. Units typically spaced 20 to 50 ft in the rows to assure full side to side mixing and prevent short circuiting. Aeration mixing zones or rows can then be widely separated for proper performance. A. Boost DO at each row of diffusers. B. Circulate with back mix toward front of lagoon as well as downstream. C. Create hydraulic barrier to minimize short circuiting. D. Zones spaced to assure bio solids settling in controlled areas between rows of diffusers. E. Settled solids digested by the circulation of lagoon contents with DO concentration of 1.0 to 3.0 mg/l design. Note: Best performance with rows of diffusers rather than uniform grid of diffusers as can manage O2 concentration and settling locations most effectively. V. Typical to place 1 row of diffusers near outlet end of lagoon: A. Boost DO prior to discharge. B. Minimize algae and floating debris near outlet, i.e. minimize loss of solids. C. Minimize short circuiting with emphasis to include units near corners of lagoon to maximize full lagoon volume utilization. 2

4 VI. Spacing of rows of diffusers along lagoon increases with distance from inlet and spacing of diffusers may also increase along the laterals. Spacing of rows and/or fewer units per row recognizes tapered demand for O2 along lagoon length. VII. O2 demand distributed and calculated using EPA lagoon manual for most systems. Reference: Design Manual - Municipal Wastewater Stabilization Ponds VIII. Multiple lagoons may require distribution of diffusers for O2 by supplying more than theoretical 100% of units. The greater the temperature variation with cold winters and warm summers the more likely to suggest increased number of units for superior flexibility & lagoon performance. Example: Lagoon #1 Summer needs 85% O2 Winter only 50% O2 Lagoon #2 Summer only 15% O2 Winter about 40% O2 This suggests maximum operational flexibility with 75% to 85 % units cell #1, then 30% to 40% into cell #2. This distribution of diffusers requires 105% to 125% of theoretical units to allow maximum operational flexibility. Shifting air between lagoon #1 and lagoon #2 delivers maximum operational efficiency as sufficient units are available for any operational condition. IX. For details on diffuser mounting/installation configuration refer to EDI technical bulletin 165. This bulletin describes the features of the basic mounting methods. A. Individual hoses to floor mounted diffuser units. B. Floor mounted diffusers fed from submerged laterals and fed by floor mounted hoses. C. Floating laterals with suspended diffusers. D. Partial submerged laterals with suspended diffusers. E. Special configurations on diffuser assemblies. X. For process design information contact EDI for process air calculations, blower sizing, type and number of diffusers, recommended diffuser layouts and system hardware cost. EDI Aeration Works also offers installation services and contract maintenance for lagoons or other aeration systems. 3

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