Description
The basic SBR models in WEST (SBR_PS_R01, …, SBR_PS_R10) progress from one phase to the next based purely on time (phase duration parameters T1 to T5 and TLaunch). The time parameters are specified by the user or can be manipulated using an external controller, however, varying the phase durations based on process conditions requires the implementation of ad-hoc control logic, adding complexity and reducing usability.
In WEST 2026 U1, we have introduced four new SBR models (SBR_A, SBR_B, SBR_C, SBR_D) with variable duration of the reaction phase(s), and options for built-in level-control, without the need for complex control implementation.
The new SBR models support variable nitrification and/or denitrification phase durations driven by actual process conditions rather than predefined time schedules. In addition, effluent flow during the withdrawal phase stops when reactor volume drops to a specified volume, preventing the reactor draining out due to an imbalance between the inflow and outflow rates. These models provide a more realistic representation of the operation of real SBRs and are easier to use, as they reduce the need for user‑implemented controllers.
The different options are:
SBR_A and SBR_C for nitrification only
SBR_B and SBR_D for nitrification and denitrification
SBR_C and SBR_D automatically switch to nitrification or denitrification (no influent) from the Fill or Launch phases once the reactor is full, preventing overflow to the effluent
SBR_C and SBR_D have separate Idle and desludge phases, allowing the phase durations to be controlled separately.
The operation of the new SBR models is summarized in Table 1 below.
Table 1 - Variable phase SBR models
Figure 1 below illustrates the phase alternation, volume variation in the tank and the ammonia and solids concentration in the influent and effluent for an SBR_C model.
Conclusion
Users can now choose four variants of SBR models with variable duration of the reaction phase, and options for built-in level-control, without the need for complex control implementation.
FURTHER INFORMATION AND USEFUL LINKS
Manuals and User Guides
Release Notes