Air Based ATAD
m²t is in the final stages of process development of a continuous flow ATAD system that uses air as the aerating gas. It will be a staged, continuous flow process that operates at relatively low total retention time. No outside heat sources are required to attain and maintain thermophilic operating temperatures. The system will feature:

• Conventional concrete or steel tanks that are covered
  
  
• Simple, dependable surface aeration equipment for aeration and mixing
  
  
• Low total retention time (~4 to 6 days)
  
  
• Continuous flow (not batch) operation

Air based ATAD is intended for use at facilities that do not currently have a source of high purity oxygen gas on site and have a requirement to upgrade to technology that produces a Class A biosolids product.

High Purity Oxygen ATAD
m²t personnel have been on the forefront of the development of high purity oxygen ATAD technology since its advent in the early 1970s. The power of high purity oxygen to conserve the heat of digestion means oxygen ATAD reaches operating temperature faster, which lowers retention times and tank volumes. m²t’s oxygen ATAD systems feature:

• Short retention times (2 to 4 days) and minimum tank volumes
  
  
• Simple, dependable surface aeration equipment for aeration and mixing
  
  
• Continuous flow operation
  
  
• A pasteurized biosolids process when operated thermophilically
  
  
• Simple process control, which minimizes operating manpower requirements
  
  
• Can easily be retrofit into existing tanks

High purity oxygen ATAD is intended for use at facilities that currently have a source of high purity oxygen gas on site (or have access to reasonably priced high purity oxygen gas) and have a requirement to upgrade to technology that produces a Class A biosolids product.

Dual Digestion
Dual Digestion is a proven, two step sludge digestion process that combines the best features of both aerobic and anaerobic sludge digestion. Dual Digestion combines a short retention time aerobic digestion step followed in series by a high rate anaerobic digestion step. The Dual Digestion system features:

• An autothermal (i.e., with no external heat source), one to two day retention time aerobic digestion step capable of operating either thermophilically or mesophilically
  
  
• A high rate, eight to ten day retention time anaerobic digestion step that completes the sludge digestion process, producing usable digester gas containing 60%-65% methane as a byproduct
  
  
• Significantly improved process stability compared to conventional anaerobic digestion
  
  
• Continuous flow operation
  
  
• Simple process control, which minimizes operating manpower requirements
  
  
• Very low total mechanical energy requirements
  
  
• Significantly greater usable digester gas than from conventional anaerobic digestion because the process requires no gas for digester heating purposes
  
  
• When operated thermophilically, the process produces a digested sludge product meeting 503 “Class A” biosolids requirements
  
  
• Offers a cost effective sludge digestion solution for either new plants or old plants with anaerobic digesters that are undersized

Dual Digestion is intended for use at facilities that currently have overloaded anaerobic digesters and/or a need to upgrade to technology that produces a Class A biosolids product.

More Information

The ATAD/Dual Digestion System Schematic

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Tacoma, Washington's Central Wastewater Treatment Plant

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