Why are submersible pumps used more often than surface-mounted pumps in sewage applications?

Submersible pumps are considered to be positive suction being installed at the bottom of a wet well and can’t lose prime.

Surface mounted pumps has the advantage of the same pump having different pumping rates by just changing the size of the pulleys. Whereas submersible pumps has to be specified for specific head pressure and gallons per minute. Seem like I read that it takes 104 different submersible pumps to do what just changing pulleys sized can do with one surface mounted pump.

APPLICATIONS:

→ Muddy water transfer.

→ Swimming pool.

→ Dewatering of ponds, the basement of the huge building.

→Power plant.

→ Effluent transfer, ETP, STP, waste water treatment plant.

→ Used in hotels, hospitals, railways, dairy, chemical and, sugar, steel, cement, food beverages, etc