Cook sausage in oil in wide 6- to 8- quart heavy pot over medium-high heat, stirring occasionally, until golden-brown, about 5 minutes. Transfer to bowl with a slotted spoon.
Cook peppers, celery, onion, scallions, garlic and ½ tsp salt in fat remaining in pot stirring occasionally, until golden-brown, 10 to 12 minutes. Stir in rice, sausage, tomatoes with their juice, water, 1 tsp salt, and ½ tsp pepper and bring to a rolling boil.
Reduce heat and cook at a bare simmer, covered tightly with lid, until rice is tender and water is absorbed, about 25 minutes. Remove from heat and let stand, covered, 10 minutes. Fluff rice with fork.