Sewage stinks. But bacteria can make it smell better.

Oh, yeah?

That's true. 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.

And you are saying we could use other bacteria instead?

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.

Using bacteria to break down the by-products of bacteria. Now that's clever.

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. But what do they give off?

Good question. And the answer is hydrogen sulfate–better known as sulfuric acid– almost odorless at the fairly low concentrations produced.

sewage:(下水道里的)污物

hydrogen sulfide:氢化硫

malodorous:难闻的

stink:臭味

by-product:副产品

payoff:结果,报偿

biofilter:细菌过滤器,生物过滤器

bleach:漂白剂

lye:碱液

sulfuric acid:硫磺酸

odorless:无味的