Mixing Limited Tanks

  • Aerobic Digesters / Aerated Sludge Tanks
  • Anaerobic Digesters
  • Anaerobic Selectors
  • Anoxic Selectors
  • Bioreactors
  • Channels
  • Chlorine Contact Tanks
  • Equalization Tanks
  • Industrial Process Tanks
  • Lift Stations
  • Mixing Limited Tanks
  • PAC Contactors
  • Potable Water Storage Tanks
  • Septage & Grease Tanks
  • Sludge Holding Tanks

    • In aerobic tanks, the aeration equipment is designed to both deliver oxygen and mix the contents of the basin. Under mixing limited conditions, more air is required to mix the basin contents than is needed to satisfy the oxygen demand. Decoupling oxygen demand from mixing requirements provides the operational flexibility to reduce the airflow rate to meet the air required for plant loading.

    A BioMix Compressed Gas Mixing System can be interlaced with diffused aeration grids, allowing simultaneous operation and preventing over-aeration — an outcome no mechanical mixing device can provide. This results in BNR process control benefits and significant energy savings.

    The BioCycle-ENR Activated Sludge Process and FlexZone Adaptive Process Volume System are ideally suited for municipal and industrial secondary treatment processes that experience mixing limited conditions. The technologies are extremely effective for plants that are underloaded compared to design, or plants with wide diurnal variations.

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    “We have reduced our operations and maintenance requirement significantly by going with BioMix.” Greg H. – South Carolina WWTP

    Causes & Solutions

    What causes mixing limited conditions?
    • Underloading compared to design conditions
    • Daily or seasonal load fluctuations
    • Hydraulic limitations that prevent taking trains out of service
    • Oxygen demand that is diminished by upstream aerobic zones
    How does excessive aeration impact a treatment plant?
    • Residual dissolved oxygen in RAS and mixed liquor return that inhibit BNR
    • Poor settling
    • Excess treatment chemicals in post-anoxic zones
    • Wasted energy
    Why is BioMix the right solution?

    The requirement for the aeration system to provide the air necessary to meet the process oxygen demand and the mixing air demand can be eliminated by decoupling oxygen demand from mixing requirements, thus providing the operational flexibility to reduce the airflow rate to meet the air required for just the plant loading. A BioMix Compressed Gas Mixing System can be interlaced with diffused aeration grids to provide mixing, allowing simultaneous operation with the aeration system at low aeration rates or independent operation. This results in:

    • Promotion of anoxic and anaerobic conditions to enable BNR
    • Elimination of high dissolved oxygen in IMLR
    • Conditions that promote good settling in secondary clarifiers
    • Stable dissolved oxygen profile throughout the aeration tank
    • Significant energy savings

    resources

    Application Sheet: Mixing Limited Aeration

    Product Brochure: BioMix Compressed Gas Mixing System

    Product Brochure: BioCycle-ENR Activated Sludge Process

    Product Brochure: FlexZone Adaptive Process Volume System

    Case Study: BioMix Selected for Norfolk, VA

    Case Study: BioMix Selected for Exeter, NH