Method and computer program product for treating liquid containing impurities

A non-transitory computer readable medium storing a computer program product for facilitating a backwash process in a granular media filter including filter media and a water treatment tank, the computer program, when executed by a computer processor, causes the computer processor to perform the following functions:

• a) determining whether movement of the filter media is detected in the water treatment tank during a backwash process, and if not, performing the following functions:
• a1) instructing an upper burst solenoid to provide a burst of airlift flow emerging from a first airlift path at a first position in the filter media at a bottom portion of the water treatment tank, and at a first point in time;
• and
• a2) instructing a lower burst solenoid to provide a burst of airlift flow emerging from a second airlift path at a second position in the filter media at the bottom portion of the water treatment tank, and at a second point in time,
• wherein the second position is below the first position and the second point in time is after the first point in time, and
• wherein the bursts of airlift flow emerging from the first and second airlift paths enable suitable movement of the filter media within the water treatment tank thus facilitating the backwash process.