LOS ANGELES — Every day Southern California hospitals unleash millions of gallons of raw sewage into municipal sewers. The malodorous muck flows miles to one of the region’s sewage plants, where it is treated with the rest of the area’s waste and then released as clear water into a stream or directly to the Pacific. Scientists at the Environmental Protection Agency recently announced they had discovered a lethal superbug – the same one that caused outbreaks at UCLA and two other Los Angeles-area hospitals – in sewage at one of those plants.