Secret Weapon Against the Smell of Sludge? Sludge
By ANTHONY DePALMA
Published: February 21, 2005
Every 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.
Safety is a big consideration, especially since several of the filters in a sewage plant in Sheepshead Bay, Brooklyn, caught fire on a hot summer night in 2003, sending acrid smoke and an unforgettably bad odor – that local residents compared to burnt rotten eggs – through parts of Brooklyn.
Since ocean dumping was banned in 1992, getting rid of sludge has become big business. Developing a new kind of odor filter from sludge is potentially profitable, so Dr. Bandosz politely declined to discuss many of the details of her project, which she is trying to patent.
But she said that the good thing about sludge, especially New York’s, is that it is such a stew of chemicals and minerals. She began her research by determining what materials would have to be added to natural carbon to make it an effective filter. She came up with a list that matched what she had found in sludge.
“We said ‘Hey, we already have everything we need right here,’ ” Dr. Bandosz recalled. ” ‘Let’s try it.’ “
In her laboratory, Dr. Bandosz keeps small sacks of dried sludge from New York and other cities, including Baltimore, Philadelphia and Wilmington, Del., to see which sludge makes the best filter. New York wins hands down. But the presence of all these samples in the lab leads to an obvious question, to which she adds an emphatic answer.
“We do not smell!” she declared. “The office of the dean of science is right down the hall. Nobody on this floor complains of smells.”
And on a recent morning, the aroma in her lab could be described as semi-industrial, but certainly not semi-noxious. Carbon filters from the city’s sewage treatment plants have been tested at City College since 1992, when a professor emeritus, Amos Turk, signed the first testing contract with the Department of Environmental Protection, which runs the sewage treatment plants.
The plastic sample jars that line several shelves in the lab have a slight chemical odor, and the treated sludge pellets that Dr. Bandosz uses to make her own filter material smell like garden manure.
In the world of applied chemistry, working with sludge filters is a respected area of research. There is fierce competition for postdoctoral research positions in Dr. Bandosz’s lab.
Conchi Ania, a postdoctoral chemist from the National Carbon Institute in Spain, has worked in the lab since May. “I already knew about Dr. Bandosz’s research, and after I met her at a conference I knew I wanted to work with her,” she said. There was only one hitch, based on an experience in Spain working alongside someone doing research into sludge.
“That smell was something I will never forget,” she said. She kept a separate set of clothes for working in the lab and never wore them home. She stocked up on Chanel No. 5.
But she has not had to take such precautions in Dr. Bandosz’s lab. Even taking samples in the sewage treatment plants is not so bad because most of the equipment is tightly sealed.
Deodorizing sludge is not everyone’s idea of exciting work, even within the scientific community. Dr. Bandosz recalled receiving a message from a colleague in London a few years ago. “I see you’re working on sludge now,” her friend had said. “What an excellent conversation stopper that must be.”
Truth be told, she said, when people find out what she does, they tend to want to know more.
And to those who might be wondering, Paloma Picasso is just about her favorite perfume.