Phased Activated Sludge System

The AquaPASS® system is a time-managed activated sludge technology that integrates select unit processes into a single biological treatment system. The system utilizes the Aqua MixAir® system by providing separate mixing with AquaDDM® direct-drive mixers and Aqua-Aerobic diffused aeration. This system has the capability to cyclically operate the aeration and mixing to promote anoxic/aerobic and anaerobic environments with low energy consumption.

How It Works

Features & Specifications

  • Aqua MixAir® system provides flexible control of aeration and mixing
  • Time-based anoxic intervals promoting exceptional nitrate reduction
  • Superior process environment suitable for cold weather climates
  • Ideal for a wide range of design flows
  • Flexible tank design and equipment options


  • Designed and engineered as a Time Based Activated SludgeSM System
  • Enhanced biological nutrient removal (EBiological Nutrient Removal)
    • Total nitrogen < 3 mg/l
    • Total phosphorus < 0.6 mg/l
  • Flow-through operation with multi-stage performance
  • Concentrated return activated sludge (RAS) provides optimized process environments
  • Membrane ready for future expansions
  • Load proportioned power savings mode
  • Simple and flexible system operation

Plant Photos


Related Resources

Resource CategoriesTitleSummaryDownload Link
BrochureAquaPASS® Brochure


Success StorySalisbury, PASalisbury retrofits existing process with an AquaPASS® system to comply with the Chesapeake Bay Initiative


VideoAquaPASS Phased Activated Sludge System Video


VideoAqua-Aerobic Systems, Inc. Overview Video


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