Place dried scallops in a small bowl and cover with water. Let soak until softened, 30 minutes to 1 hour. Drain and cut into small pieces.
Bring a large pot of water to a boil. Add pork spare ribs; cook for 5 to 8 minutes. Drain and rinse under cold water.
Combine scallops, spare ribs, and lotus roots in a pot. Add three times the volume of water; bring to a boil. Cook at a boil for 30 minutes. Reduce heat to medium and simmer, adding more water if needed, until lotus roots are soft and water is reduced by a third, 2 to 3 hours. Stir and season with salt.