In a large soup pot, saute the onion, carrot, celery, and garlic until tender. Add lentils, water, and bay leaf. Bring to a boil and simmer, covered, for 30 minutes. Add kielbasa, cover, and simmer for another half hour, until lentils are tender. Season to taste. Remove kielbasa ring, cut into chunks, and return to pot. Serve with crusty bread.