The decanter is a key piece of equipment within a sequencing batch reactor (SBR) system, removing clarified effluent from the basin during the decant phase of the operational cycle.
The ABJ ICEASRegistered process is an advanced SBR technology with continuous inflow. The ICEAS process is operated using defined cycle times adjusted to variable flow conditions. Each cycle typically consists of three main phases; aerate, settle and decant. The basin is aerated continuously during the first half of the cycle. After the aeration phase, the system goes into a settling phase where liquid/solids separation occurs. In the final step, clear water is decanted out of the basin.
The decanter typically is installed on the basin wall supported by an effluent box on one end and by a pedestal on the other. The decanter is lowered and raised using an electro-mechanical actuator. The actuator moves between top and bottom limit switches whenever the decanter is in operation, ensuring that the decanter travels from the "park" position to the bottom water level (BWL). The decanter parks above top water level during the aeration and settling phases of the cycle, thereby eliminating any possibility of solids carryover during these periods.
The decanter speed is controlled through use of a variable frequency drive (VFD). As a result, the decanter discharge rate is relatively constant from the time the decanter enters the water to the time it reaches the BWL.
Operation
During the decant phase, after receiving a signal from the control system, the decanter travels from the "park" position to the design BWL. Upon reaching the BWL, the decanter pauses for a few minutes to ensure completion of the discharge flow over the weir. The decanter then returns to the "park" position, where it remains until the start of the next decant phase. Redundant limit switches on the actuator ensure reliable operation whenever the decanter is in motion. The limit switches fully integrate with process control time overrides and interlocks, thereby eliminating the potential for blower activation during decant.
At "park" position, the decanter provides "fail safe" overflow protection in the event of a power failure. Settled supernatant will flow over the decanter weir and into the effluent collection system. The decanter scum guard float prevents carry over of any floatables during such emergency periods.
The decanter weir always is visible from the basin walkway. This feature provides the operator with a continuous visual check of the effluent quality.
The decanter mechanism can be used to optimize disinfection system operation downstream of an SBR process. A float switch installed on the decanter weir will contact the water surface before the decanter, thereby activating the disinfection system prior to discharge of the treated water.
Decanter features include stainless steel construction for corrosion resistance; an electromechanical actuator with redundant limit switches; and variable frequency drives (VFD) for speed control.
The ABJ decanter decants from the top downward, withdrawing only the uppermost clear water from the basin and preventing disruption of the settling solids. All maintenance can be performed from the walkway without entering the basin. The decanters ship with all of the major components pre-assembled.
