PACT® Sequencing Batch Reactor is a modification of activated sludge process which has been successfully used to treat municipal and industrial wastewater. The difference between a conventional technology and SBR is that the SBR performs equalisation, biological treatment and secondary clarification in a single tank using a times control sequence. It has been very useful in the areas where there is limited amount of space. PACT Sequencing Batch Reactor is a fill and draw activated sludge system. In this system, the waste water is added to a single batch reactor, treated to remove undesirable components and then discharged. There are five stages in the treatment process: fill, react, settle, decant, idle.

The inlet valve opens and the tank is being filled in, while mixing is provided by mechanical means (no air). This stage is also called the anoxic stage. Aeration of the mixed liquor is performed during the second stage by the use of fixed or floating mechanical pumps or by transferring air into fine bubble diffusers fixed to the floor of the tank. No aeration or mixing is provided in the third stage and the settling of suspended solids starts. During the fourth stage the outlet valve opens and the “clean” supernatant liquor exits the tank. The separate treatment of the nitrogen-rich return liquors from sludge treatment represents a special application, which allows increased overall nitrogen removal and a reduction in biological treatment stage loads. Nitrogen removal can be achieved either conventionally with an external substrate for denitrification or using the innovative Anammox process.


  • Equalisation, primary clarification, biological treatment and secondary clarification can be achieved in a single reactor vessel.
  • SBR requires small space.
  • SBR has controllable react time and quiescent settling.
  • Minimal footprint.
  • High nutrient removal capabilities.
  • The BOD removal efficiency is generally between 85- 90%.
  • Filamentous growth elimination.
  • A higher degree of operational flexibility with respect to effluent quality and dissolved oxygen (DO) controlled aeration system
  • Proven treatment process capacity upgrades and phasing do not require modification or interruption of current treatment process
  • Power consumption is typically less than that of a conventional plant with substantial power savings at lower flows


  • Municipal wastewater including Biological Nutrient Removal
  • Water recycle & reuse
  • BOD & COD reduction
  • Industrial Wastewater
  • Food & Beverage
  • Pulp & Paper
  • Petrochemical & Oil refining
  • Chemical/ CPI
  • Landfill/ Leachate applications
  • Textile Industry