Applications with standard function:
Variable speed decanter improves WWTP efficiency
Various sites across the world
Water treatment works using SBRs (Sequencing Batch Reactors) draw off treated water from above the settled solids using a decant arm. This structure must be lowered into the water slowly (typically over around one hour at a constant speed) without disturbing the settled solids at the bottom of the tank.
However, to ensure fast refilling, the arm needs to be raised rapidly to a preset parked position above the water prior to the next decant cycle.
Under normal operation when a reduced flow is detected, the actuator which controls the valve is opened over a period of 80 seconds, however, if a reverse flow is detected then the valve needs to be closed in 10 seconds to protect the pump.
Different speeds are therefore required for opening, closing and emergency closure to protect the pump.