Secret Weapon Against the Smell of Sludge? Sludge
By ANTHONY DePALMA
very city is saddled with aspects of urban life that are as undesirable as they are unavoidable - things, for instance, like sludge, and the stink that goes with it. Most people do not want to even think about how a city the size of New York gets rid of 1.2 billion gallons of everything that goes down the toilet, drain or gutter every day, and they certainly do not want to smell it.
And on most days, at most times, they do not, because sewage treatment plants are buttoned up tighter than a walk-in cigar humidor and people like Teresa J. Bandosz are there to make sure that what goes on inside stays inside.
Dr. Bandosz, a research scientist and professor of chemistry at City College, is New York's unofficial odor warden. With a small team of student researchers and a technician, she monitors how well carbon filters at the treatment plants keep foul odors from spewing into the air.
Dr. Bandosz has also been trying to figure out how to make the smell-scrubbing process more efficient. Like a modern-day Edison, she has experimented with an odd assortment of materials to make the best filter. She has tried scrap paper and recycled plastic, then moved on to coal before going out on a limb and trying the pits from olives and peaches after she and her assistants ate around them.
Now she thinks she has come up with just about the perfect material for taking the stink out of sludge - sludge itself. She starts with fertilizer pellets that the New York Organic Fertilizer Company in the Bronx makes from the city's treated sludge.
In an oxygen-free container, she heats the tiny pellets to more than 1,700 degrees, which helps them filter out offending compounds, primarily hydrogen sulfide, more efficiently. Each piece of treated sludge becomes like a microscopic sponge, filled with cavities that absorb the stuff that gives sludge its awful smell. "We ran the tests and we've had fantastic results," said Dr. Bandosz, 44, who came to the United States from Poland in 1991. She said she has wanted to be a chemist since a teacher showed her the invisible world of compounds and molecules when she was 12.
"You had to use your imagination to link what you knew with what you couldn't see," she said.
The compounds she is working with now are so complex that there is still some mystery about how they react. She is not certain exactly why, but the filter made from sludge is more effective than carbon filters. She thinks it will be cheaper than the carbon now used in the filters at the treatment plant. The city buys carbonized coconut shells and other materials for its filters.
There is still much work to be done before the city can use sludge as a deodorant. So far, Dr. Bandosz has been able to produce only a few grams of the filter material in her lab on the 13th floor of City College's science building.
New York now has a total of 1,400 tons of carbon in use in the 140 filters in its 14 treatment plants. Even after the treatment plants separate liquids from solids and decontaminate the sludge that is left, there still are plenty of noxious fumes that have to be scrubbed before they can be released into the atmosphere. The final step is to pass them through the carbon filters.
Alfonso R. Lopez, deputy commissioner of wastewater treatment for the city's Department of Environmental Protection, said that he found Dr. Bandosz's ideas interesting, but had some reservations, since he had not seen a full demonstration.
He was not sure that the treated sludge would be effective against compounds other than hydrogen sulfide. And the city does not have the equipment to produce large quantities of the carbonized fertilizer pellets; Mr. Lopez worries that producing them would create odors that would annoy city residents. Neighbors already complain about smells from the Bronx plant where they are made.
Dr. Bandosz said the sludge pellets would probably have to be combined with other material to get at the volatile organic compounds in the sludge that can also cause it to stink. Even so, she said, using sludge pellets would give the city sewage treatment plants that control odors more efficiently, and are both cheaper to run and safer to operate.
