Complex sentence: The Jones Island Plant was the first sewage treatment plant in the United States to succeed in using the activated sludge treatment process to produce an organic fertilizer, and had the largest capacity of any plant in the world when constructed.
Split into simpler sentences: The Jones Island Plant was among the first sewage treatment plants in the United States to succeed in using the activated sludge treatment process. It had the largest capacity of any plant in the world when constructed.