【英语时差8,16】细菌让污水不臭（在线收听）

Certain forms of bacteria feasting on sewage give off hydrogen sulfide, a really malodorous chemical, and one of several that give sewage its “pleasing” smell. In general this problem has been treated with powerful chemicals like bleach–not at all good for the environment. That's what Marc Deshusses, of University of California Riverside, argues and his technique is catching on. There’s already a sewage treatment plant in California that’s using bacteria that degrade hydrogen sulfide, using the oxygen in air, to get rid of the stink. Nor is the payoff only environmental. Using “biofilters,” as this kind of system is called, means plant operators can decrease the amount of dangerous chemicals onsite. Biofiltering is also cheaper than chemically treating the problem with bleach or lye. Some bacteria break down sewage. They give off hydrogen sulfide. Other bacteria break down hydrogen sulfide.Hydrogen sulfate–better known as sulfuric acid– almost odorless at the fairly low concentrations produced.