Tales from the
Philadelphia's sewer system
has swallowed one Volkswagen, countless shopping carts and a billion
dollars' worth of improvements. Now the city has to figure out how to sell
a heap of fertilizer.
The Philadelphia Inquirer Sunday Magazine
February 19, 1989
NOT MANY PEOPLE keep count, but
the average Philadelphian flushes a toilet about six times a day. Every
flush sends about five gallons of water down the drain. Including bathing,
laundry and cooking, the gallons add up. Researchers for the Philadelphia
Water Department know that all told, each person uses something like 94
gallons a day. After flushing, most people don't give it any thought.
Norman Lofton does.
Lofton holds one of society's lower-profile jobs. Five days a week, he
puts on a pair of chest-high rubber waders, a yellow raincoat, a hard hat
and a pair of gloves and climbs underground. Lofton is a sewer-maintenance
crew chief for the Water Department - a "sewer crawler," in the slang of
"I wouldn't say anybody likes it," said Lofton. "You'd have to be crazy
to like it."
Lofton holds the record for the department's longest continuous sewer
inspection. In 1987, he and his crew entered a pipe in a railroad yard
near Queen Lane and came up for air around Henry Avenue, 5,745 feet later.
Lofton measured it. "Sixteen hundred and forty feet was examined bent
over," he said. "Some of the sewer was built out of Belgian block, and it
was very slippery with waste water and feces. It was like walking on ice.
It took us two hours and 15 minutes."
As Lofton spoke, he was standing in a chamber 26 feet below Wissahickon
Avenue near Queen Lane. The light from the manhole above was so diffuse
that the pits and ridges in the rough-cast concrete were barely visible.
Though they wore yellow rain slickers, the three members of Lofton's crew,
who were joining him at the bottom, moved about like gray phantoms.
Lofton tested a black box called a Dynamation meter, an electronic
canary that shrieks if various gases in the sewer approach dangerous
levels. The air can be so foul beneath oil refineries, slaughterhouses and
chemical plants that the crawlers use scuba equipment. The hot sewage from
laundries can block a pipe with steam and suds and scald the crawlers. On
this day beneath Wissahickon Avenue, the air was dank but odorless. The
box in Lofton's hand remained silent.
"People have no idea what it's like down here," said Lofton, 38, who
has worked in the city's sewers for 18 years. "It's another city. It's a
private city." Several small pipes entered the chamber from different
directions. Sewage cascaded from each and swirled in a pool around
Lofton's waterproofed ankles. Turbulence had rendered everything in the
sewage beyond recognition. It looked like cafe au lait. The sewage flowed
into a larger pipe that continued downhill.
Lofton aimed a flashlight into the darkness of the big pipe. "That's
where we're going."
AT ONE TIME, THIS SEWER HEADED
straight into the Schuylkill. In 1955, it was tied to the Southwest Sewage
Treatment Plant near Philadelphia International Airport. There, after
minimal treatment, the sewage was dumped into the Delaware.
Nowadays, the sewage at Lofton's feet takes a much more circuitous
route through a tremendously complex treatment system. The stuff is
screened, floated, skimmed, separated, pumped full of air and then fed as
lunch to a quintillion hungry bacteria. After that, it is tested,
disinfected and released into the river.
In the last 15 years, Philadelphia's waste-water-treatment system has
been overhauled at a cost of nearly $1 billion. When the work is completed
this summer, it will rank as the largest public-works project in the
city's modern history. The cost is twice that of the city's proposed
convention center, three times the price of the Center City commuter
tunnel and four times the cost of the Schuylkill Expressway
Now, sewage-treatment plants are called "water pollution control
facilities," but a billion dollars has bought more than a euphemism. The
overhauled system has dramatically improved the water quality of the
Schuylkill and the Delaware. Fish have returned in large numbers. The
cleaner waterways have, in turn, spawned waterfront development that would
not have been possible 40 years ago, when the Delaware stank so badly it
nauseated pedestrians at Broad and Chestnut Streets.
With much of the work buried, the project has escaped pageantry. Water
Department officials are not naive about the capacity of sewage to inspire
civic pride. They would be happy if nobody complained. "Success in sewage
treatment is defined as not being noticed," said William J. Marrazzo, who
was, until November, the city's water commissioner for eight years. But
sometimes sewage can't be ignored.
When the winds are right, it is hard not to notice the city's three
treatment plants. Each day, 466 million gallons of waste water flow into
them from Philadelphia and parts of three surrounding counties, a volume
equal to the daily flow of the Schuylkill in the summer. If One Liberty
Place were an empty shell, the flow would fill all 62 floors in less than
Of that load, only a tenth of one percent is solid matter - sludge. It
is enough, however, to give sewage a bad name. But while New York dumps
its sludge into the ocean, and Boston sends its muck right into its
harbor, the Philadelphia Water Department composts its "sludge products"
and markets them as fertilizer. The cutting edge of environmentalism,
however, can cut both ways: The city has been hard-pressed to find enough
large-scale users in places where people won't raise a stink.
In order to collect that sludge, the city routes its sewage - your
sewage - through 2,933 miles of pipes beneath Philadelphia. In a system as
long as the nation is wide, there are bound to be backups, leaks, clogs
and overflows just about every day.
Norman Lofton knows that well.
IN THE CHAMBER BELOW WISSAhickon
Avenue, Lofton bent over and scurried into the pipe. The
4-foot-3-inch-high sewer was constructed of brick in 1894, when indoor
plumbing was considered modern. Like all sewers, it was built at a slight
slope to keep sewage moving downhill. It originally was circular, but over
the decades, the earth above has compressed it into an oval.
The only noise was the splashing of Lofton's boots and the constant
gurgling of sewage. Now and then, reminders of life on the surface
penetrated the eerie world - the clang of an automobile running over a
manhole cover, the sight of a steel I-beam piercing the pipe, the
foundation of some structure overhead. Occasionally, small sewers
protruded at head level from the sewer wall - the drains from nearby
buildings. You may not think about your six flushes a day, but they are a
matter of great concern to a sewer crawler. Fortunately, the unmistakable
rumble of a flush is amplified in the pipes. Most of the time, the
crawlers can move out of the way.
Lofton pointed to cracks in the sewer wall where clear water dribbled
into the pipe. About 5 percent of the waste water enters the system
through leaks. Some of it is groundwater; some of it is treated city water
- pure, drinkable water - leaking from damaged mains. Sometimes, a leak in
a main washes out so much soil that it forms an underground river between
the water main and the sewer. Almost every year, one of the washouts
collapses, sometimes swallowing a car in a sinkhole. Lofton and his crew
make recommendations on major repairs and make smaller patches themselves.
In a system as old as Philadelphia's, where many of the sewers were built
in the 19th century, there's plenty of work to do.
As Lofton forged ahead in the slowly descending sewer, the sewage at
his feet began to grow deeper and slow down. He aimed his flashlight
ahead. Beyond the reach of the beam, the stream roared over an unseen
obstruction that was damming the pipe. The blockage might be anything - a
branch, a milk crate, a collapsed wall.
"It can be very dangerous down here," he said. An obstruction like the
one ahead could dislodge without warning, unleashing the dammed sewage and
sweeping away anyone standing in it. Lofton sloshed ahead a few feet, but
when his flashlight showed the level of sewage reaching above the middle
of the pipe ahead, he called it quits.
"You can't underestimate a sewer," he said. "There's always surprises."
Since 1985, two people have died in sewers - a child who fell into a
damaged manhole and a college student who clambered into an open sewer
drain. Both were washed away. Crawlers fear cave-ins and flash floods. In
May, Lofton was examining a 10-foot sewer under Third and Thompson Streets
when the sewage surged from about a foot deep to more than three feet.
Lofton fell down face first. The sewage carried him about 45 feet down the
pipe before he could get a foothold. When he stood up, his rubber suit was
filled with sewage. "That was the first time I was ever knocked off my
feet," he said.
Inspecting sewers has few rewards - crawlers make about $21,000 a year.
In 1971, however, two crawlers came upon some muddy bundles under
Torresdale Avenue that turned out to be $92,400 in cash. Nobody claimed
the dirty money, and the crawlers were allowed to keep it.
Besides cash, strange and awful things often show up in the sewers.
Shopping carts and body parts have washed up at the treatment plants.
Since the 1973 Supreme Court decision legalizing abortion, treatment-plant
operators have noted with relief a dramatic decline in the number of
fetuses. Some of the sewers are so large they could accommodate a two-lane
highway. In fact, a Volkswagen body once was found lodged in one of the
pipes. No one could account for it.
Even to the experienced, sewers can be unsettling. "If you turn out
your light, it's dark," said Lofton. "I mean pitch dark. You can't see
your hand in front of your face."
The conditions can twist even a sensible person's brain. When sewer
crawlers apply for the job, they must be able to crawl through a pipe 18
inches in diameter. Some applicants have the physical dimensions but,
during underground tests, freeze in claustrophobic panic. Doctors say it
isn't true, but crawlers believe that panic leads a human to swell up.
They said a crawler once became so frightened that he expanded like a cork
and cut off the air to the man behind him. The trailing crawler passed
out. Both had to be pulled out of the pipe by the safety ropes crawlers
wear on the job.
Lofton is a stout man - he has a 36-inch waist - so he confines his
inspections to larger sewers. Still, he occasionally finds himself in a
tight squeeze. "A lot of times, I've gotten scared, I mean really scared.
I started swelling up. And then I talk to the Creator. I talk myself
through those sewers." The sewers have brought Norman Lofton closer to
There is considerable lore about the subterranean world. Some of it is
true. In Paris, burglars once bored a hole from a sewer into a bank. In
New York, the homeless have been found living in sewers.
Most of the stories, however, are greatly embellished. Contrary to
common belief, Philadelphia's sewers do not surge during half time of the
Super Bowl. The sewer system is so large that a citywide flush would be no
different from a short-lived downpour. Half time at the Army-Navy game is
another matter. The effect of 100,000 spectators' rushing for relief
during intermission has overflowed the trunk lines leading away from JFK
Many of the stories about underground creatures are also larger than
life. Crawlers say they have seen cockroaches the size of mice and rats
the size of cats, but reptilian life is no match for sewage. Somebody once
dumped a 12 foot pet python into Philadelphia's sewers, but when it washed
up at the Northeast treatment plant, not even biologists from the
Philadelphia Zoo could revive it. Everybody has heard stories about
alligators in the sewers, but nobody has ever seen one.
"I'm not saying my mind hasn't seen alligators," said Lofton. "There
are a lot of strange noises here, and you spend a lot of time looking over
PICTURE PHILADELPHIA AS A human
body. Its water system is the arteries, carrying pure water to each
household, each cell in the body Philadelphia. Its sewer system is the
veins, returning soiled water to be cleansed at the three sewage-treatment
plants, the kidneys of the system.
For most of its history, Philadelphia had no kidneys. The sewers of Ben
Franklin's time were constructed of wood - they were open ditches designed
primarily to carry away garbage, wash water and rain - and flowed toward
the nearest creek. (Outhouses were built over pits, and human wastes
remained in them.) As the city grew, the creeks that crossed Center City
became choked with sewage. The city turned them into sewers, one by one.
Dock Street was once such a stream.
In 1867, the city had only 67 miles of sewers. But then indoor plumbing
replaced outhouses during the industrial age, introducing human waste to
the system. By 1900, the city had 848 miles of sewers, many of which are
still in service today. Most of the pipes are brick and shaped like the
cross-section of an egg, with the narrow end pointing down. The shape
forces even low volumes of sewage to flow fast.
Since the Mesopotamian Empire, when the first drainage systems were
constructed, engineers designed sewers for one purpose: to transport
sewage downhill as quickly as possible. Following the contour of the land,
relying only on gravity for propulsion, sewers emptied in whatever stream
Unfortunately, Philadelphia's sewage went into the same rivers from
which it drew its drinking water - the Schuylkill and the Delaware.
Thousands of people died each year from waterborne diseases, such as
typhoid and yellow fever.
In the 1880s, a few years after the discovery of typhoid bacteria, the
city built a giant sewer along the east bank of the Schuylkill to
intercept the pipes that emptied into the river from industrial Manayunk.
The interceptor channeled the sewage downstream and emptied into the river
just below the Fairmount Water Works intakes, protecting Center City's
drinking-water supply after a fashion. A few years later, a second
interceptor was built along Wissahickon Creek.
Still, sewage discharges into the Delaware threatened the city's
largest water intakes in Torresdale. "What was crazy was that raw sewage
was being discharged into Pennypack Creek, and when it came out to the
Delaware, it went right into the Torresdale water intakes," said William
Wankoff, the city's chief of sewage treatment. "Talk about recycling."
In 1907, the state directed Philadelphia to treat its sewage. Seven
years later, the city developed a plan to channel all of the sewage to
three treatment plants. A network of interceptors would tie the old sewers
to the new plants. Where gravity would no longer work, huge pumps would
propel the sewage over hills.
The Northeast plant, at the junction of Frankford Creek and the
Delaware River in Bridesburg, opened in 1923. It processed only about 15
percent of the city's sewage. The Depression, Philadelphia politics and
World War II delayed construction of the other two plants for 30 years.
During the delay, it became plainly evident that Philadelphia's sewage
was a serious environmental problem. In the 1940s, the Delaware River
turned black. Hydrogen sulfide gas corroded metal on houses near the
river, longshoremen fell sick, and ships' engines clogged from floating
debris. Water quality is measured by the amount of dissolved oxygen it
contains. A clean river has about 8 parts per million of oxygen. Fish
labor to breath in a river with fewer than 4 parts per million. In the
late 1940s, a 20-mile stretch of the Delaware River along Philadelphia
contained no measurable oxygen. It was anoxic, like a septic tank.
After the war, Philadelphia finally built the two other treatment
plants, the Southwest plant on Enterprise Avenue by the airport and the
Southeast plant on Pattison Avenue, south of the Walt Whitman Bridge. They
opened in the mid-1950s.
Finally, the city was treating its sewage. But the transition posed a
new problem that has plagued the city to this day.
Until the advent of sewage treatment, sewers were designed to empty
both sewage and rainwater directly into a stream. With the new design,
everything would go to the treatment plants. During dry weather, when the
only sewage in the pipes comes from houses, the flow is fairly
But even a one-inch rainfall in one day can send half a billion gallons
down the sewers - as much as the city's treatment plants are designed to
treat properly. Without some means of relief, a huge storm would fill the
new sewers to the brim, overflowing into streets and houses and flooding
the sewage treatment plants.
"I guess Noah saw something like that," said Jim Downs, a maintenance
supervisor at the Southwest plant. "I don't want to."
The city's solution was to install 176 regulator gates where the old
sewers had flowed into the rivers. Regulators are valves designed to
remain closed during the first minutes of rain, forcing sewage that is
already in the pipeline to be flushed to the treatment plant. The initial
slug of sewage from a rain is called the "shock load" because it is
heavily polluted with oil, dirt and trash rinsed from the streets. After
the shock load passes to the treatment plant, the regulators open and
discharge directly into the river. Theoretically, regulators allow only
rainwater (and, inevitably, a small amount of sewage) to escape into the
In practice, however, regulators are finicky devices - some of them are
60 years old - and they sometimes open too soon. The shock load goes right
into the river, where it lives up to its name. What's worse, the regulator
gates often become jammed open with debris and do not close after the rain
stops. Then they are like open wounds, bleeding sewage into the river
until somebody notices, which may take days.
Last year, the Delaware River Basin Commission estimated that 30
percent of the oxygen-devouring pollution that Philadelphia discharges
into the rivers is raw waste from sewer overflows and that more than half
the leakage occurs during dry weather.
The most obvious solution is to build a separate sewer system for storm
water. Almost all suburban areas and much of Northeast Philadelphia have
separate sewer systems, but nearly half of Philadelphia's sewers are
combined sewers. To build a separate storm water system would cost more
than $4 billion.
Instead, the Water Department is spending about $2.5 million to
overhaul some of the oldest regulators. The program includes installing
computerized sensors to detect if waste water is leaking into the river so
the city can dispatch a repair crew immediately, rather than discovering
the leak days later. The project, however, is moving slowly.
The U.S. Environmental Protection Agency recently drafted new
regulations that address storm-water pollution, but the improvements do
not necessarily involve high-tech hardware. Some solutions are as basic as
educating the public not to throw waste like old crankcase oil down the
street inlets. The oil simply remains in the sewer inlet until the next
storm, when it is washed into the river through a regulator.
"People may think that oil goes to the treatment plant," said Deputy
Water Commissioner Patrick Cairo. "But it doesn't. It goes into the
SOME PEOPLE GROW UP longing to be
lawyers, or dancers, or firefighters. Nobody in the Philadelphia Water
Department - nobody who will admit it - grew up burning with a desire to
work with waste water.
"I thought I would go into construction," said William Wankoff, 43, who
graduated from Drexel University in 1968 as a civil engineer. "I was
enamored with the idea of sitting on top of a bulldozer." But in the late
1960s, with the federal government pressuring local governments to clean
up polluted streams, water-pollution control was the emerging growth
industry for engineers. Wankoff found work with the Water Department. He
returned to Drexel for a master's degree in environmental engineering in
the early 1970s. Today, he is responsible for operating the city's
treatment plants, where he bulldozes through paperwork.
Jim Downs was a 25-year-old Culligan Man when he saw a city want ad for
somebody with experience in "water treatment." That's me, he said. Soon he
learned the water he would be treating required more than softening. "You
go home and your friends find out you work at the other end of the
tunnel," he said. "They all kind of moved away from me." After nine years,
he is now the head of preventive maintenance at the Southwest plant.
"We're not in it for the glamour," joked D. Robert Thompson, the head
engineer of what is called the collector system - all the pipes between
your house and the treatment plants. Thompson grew up in Doylestown
tinkering with anything he could dismantle. At Lehigh University,
preparing for a career as a structural engineer, he was introduced to
hydraulics and sanitary engineering.
Thompson joined the department in 1978, when the water commissioner was
Carmen F. Guarino. Guarino was considered a capable leader among
waste-water treatment experts, but his relationship with federal
regulators and environmentalists was antagonistic. Guarino left in 1980,
and the next year, Mayor William H. Green appointed William Marrazzo, a
31-year-old boy wonder who had received his chemical engineering degree
during the age of environmental awareness.
Marrazzo changed the Water Department's outlook. "What we don't want as
managers in this department are people who can only understand what's
going on underground," he said in 1981. "We want managers who understand
the impact their work will have on the environment and the community."
Thompson fit the bill. Now, at the age of 33, he oversees 25 people - a
position that would be difficult for someone his age to match at a private
engineering firm. His car has one of those yellow road signs stuck to the
window, only his says, "Sewer Expert on Board."
He joined Marrazzo's team of young engineers as it went about
overhauling the system. Philadelphia's treatment plants had been
considered state-of-the art in the 1950s, but over the ensuing years, the
art changed radically.
In the old days, sewage received what is now called "primary treatment"
- a settling out of the solids that removes less than half the oxygen
depleting pollutants. Meanwhile, sewage was getting progressively more
noxious. Industries poured all sorts of chemicals and organic waste down
the drain. Water users paid the same rate whether they emptied the baby's
bath or the rinse bath from an electroplater, loaded with heavy metals.
In the late 1960s, the Delaware still averaged less than 1 part per
million of dissolved oxygen during the summer, when oxygen depletion is
worst. To shad migrating upstream, the water off Penn's Landing could just
as well have been a brick wall.
The Delaware River Basin Commission ordered the city to upgrade its
treatment plants in 1968. The improvements would involve "secondary
treatment" - biologically decomposing the sewage to remove 90 percent of
the pollution. In 1970, the city agreed to make the improvements by 1977.
Congress put more pressure on the city in 1972 when it passed the
Federal Water Pollution Control Act, the landmark legislation that has
provided more than $40 billion to local agencies to finance
sewage-treatment improvements. Enforcement fell to the EPA.
The EPA and the city have had a titanic struggle since. The EPA sued
the city when it did not meet the 1977 deadlines, accusing it of dawdling.
The city countersued, accusing the federal government of singling out
Philadelphia, and contending that the EPA was "hindering and delaying" the
project. After a decade of lawsuits and extended deadlines, the two sides
were still using the same arguments last summer.
That may change under John Plonski, the former head of the Licenses and
Inspections Department whom Mayor Goode has appointed to replace Marrazzo.
Plonski, 41, the former city manager of Norristown, is the first
non-engineer to lead the Water Department, and he said his priority is to
clear its legal docket. "My coming in here offers these agencies and the
city an opportunity to settle up and put the past behind them," he said.
One thing can be said about the lawsuits, however. They got results.
The city is scheduled to finish the improvement project this summer, with
the completion of sludge-handling facilities at the Southwest plant. The
city says the troublesome plant, the target of the EPA's most recent suit,
will then be able to meet its discharge standards.
And while the water quality in the Delaware has yet to reach its
targets, it is getting close. Nowadays, dissolved oxygen rarely dips lower
than 3 parts per million. The levels of fecal coliform have dropped enough
so that most stretches of the river are considered "swimmable." The
Delaware River Basin Commission found 36 species of fish in the
Philadelphia stretch of the river in 1985, twice as many as were found at
any time during the two previous decades. The change in the fish
population was so dramatic, said David P. Pollison, the commission's head
of planning, that officials resurveyed the river in 1986 to confirm the
"In the grand scheme of things, in the big picture," said Peter Ludzia,
a compliance officer in EPA's Philadelphia office, "Philadelphia's
improvements have had a pretty significant impact on the water quality in
Whether the investment has been sufficient, however, remains up to the
federal government. The EPA is now considering whether to require sewage
to receive a third level of treatment that would introduce chemicals to
reduce levels of phosphorus, nitrogen and some of the pollutants that slip
past secondary treatment. It could add hundreds of millions of dollars
more to the project.
IN THIS LINE OF WORK one develops
various mechanisms to deal with the public's impressions about the raw
material. The Water Department's policy is to treat matters clinically.
Another approach is to join the crowd and make fun of sewage.
At the beginning of a course he teaches on waste-water treatment, James
S. Nicolo, who was the manager of the Southeast plant last year, promises
his students: "When you're done with this class, you'll really know your
Nicolo is a clever teacher who enjoys describing the science and the
nuances of waste water. Relaxed, cheerful and not one to take things too
seriously, Nicolo discovered sewage as a second career. A graduate of
Villanova's engineering school, he worked for the Navy until 1978,
designing parts for F-14s and F-16s. But he was bored. When he was 30
years old, he took a $2,000 pay cut to work for the Water Department. He
now says, "It was probably the best thing I ever did."
Rather than designing airplane parts, Nicolo helped redesign the
Southeast plant, the city's smallest and newest. A few months ago, he was
transferred to manage the Northeast plant, the city's largest plant and,
because of its proximity to residential areas, its most problematic.
At Southeast, Nicolo learned sewage treatment from the ground up. "The
most important thing about working at a sewage treatment plant is personal
hygiene," he said on a tour of the plant. "When I first started working
here, I went to the john after being out near the tanks: First, I went to
the toilet, and then I washed my hands. One of the men said, 'You're new
here, aren't you? Around here, we wash our hands before we go to the
After that, Nicolo became familiar with every aspect of Southeast.
The plant is designed to handle 120 million gallons of sewage a day
from a 21-square-mile area of Philadelphia and a sliver of Montgomery
County. Sewage from as far as Chestnut Hill and the Wyndmoor section of
Springfield Township takes up to 15 hours to travel to Southeast. In its
final sprint to the plant, the waste water rushes through an
11-foot-diameter pipe that passes beneath Delaware Avenue.
The sewage enters Southeast's headworks at 37 feet below ground level,
in the basement of a cavernous pump house. Nicolo led the way down a
concrete stairwell to the basement where roiling, churning sewage was
entering in a chamber called a wet well.
"That stuff comes in real fast, at 49,000 gallons per minute," said
Nicolo. He had to shout to be heard over the droning electric pumps that
elevate the sewage to ground level so it can flow through the rest of the
treatment plant. During power outages, the pumps shut down, but the sewage
keeps rushing into the basement of the pump house. It rapidly fills up the
wet well. "All you can do is run like hell," said Nicolo. "It rises fast.
It chases you up the steps." It happens often enough that the concrete
walls of the stairwell are flecked in brown to a line about 12 feet above
the top of the well.
Before the pumps draw the sewage to the surface, the waste water passes
through iron screens that collect any debris wider than one inch, which
might damage the pumps. A mechanical rake periodically clears off the
trash. Most of the debris is street junk - lumber, beverage cans, rags and
a fair amount of cash. "You'd be surprised," said Downs, "how many guys
make it a part of their day to go walking through the screen room,
especially after a big rainstorm."
Until this point, the sewer system has been designed to maintain a
quick enough flow to keep all the solids afloat. The basic treatment
process that follows - primary treatment - involves little more than
slowing down the sewage to settle out progressively smaller particles.
The first step is the grit chamber, a large pool where gravel, sand and
bits of glass settle to the bottom. If you dropped your wedding ring down
a sewer, this is where it would stop. Grit is removed and sterilized in an
incinerator before it is sent to a landfill.
Next, the sewage slows to a crawl in the primary settling tanks. The
tanks are 12 feet deep and 250 feet long. During the two hours it takes
sewage to pass through the primary tanks, suspended solids slowly drift to
the bottom. Grease, tampon applicators and condoms - technically called
scum - float to the top. Automated wooden boards slowly skim the scum from
the top and then scrape the sludge away from the bottom. After it is
collected, it is incincerated. Since a lot of it is grease, it burns
Primary treatment involves only the physical removal of solids. In the
last 15 years, Philadelphia has converted its three plants to include
secondary treatment, or the biological decomposition of sewage. Southeast,
which began secondary treatment only two years ago, was the last plant to
undergo the improvements.
Secondary treatment essentially attempts to duplicate the cleansing
process that naturally occurs in a river. Microorganisms in a stream feed
o9converting the waste into carbon dioxide and solids. But the microbes
also consume a stream's dissolved oxygen. Heavily polluted streams lose so
much oxygen that even the microbes die and the cleansing action all but
ceases. They become septic, like the Delaware River during the 1940s.
The key to this cleansing process are the microorganisms - bacteria,
protozoa and algae. Treatment plant operators once were nuts-and-bolts
kind of people, but secondary treatment has forced them to learn as much
about microbiology as mechanical engineering. The microbes that consume
sewage have a host of complicated names, but to treatment plant engineers,
they are simply "bugs."
After primary treatment, the sewage flows into aeration tanks, where it
is pumped full of oxygen - so much that the microbes not only survive, but
also breed like crazy and gobble up the sewage. After this microbial
feeding frenzy, the sewage, which is now called "mixed liquor," flows into
a settlement tank, where the end product - sludge - sinks to the bottom.
Without the sludge, the water in the settlement tanks is ready to be
released back into the river. One might presume that the sludge would be
disposed of - "wasted," as they say in the trade. In truth, much of the
sludge, teeming with bugs, is pumped right back to the aeration tanks to
breed a new generation of bacteria. "You settle those bugs out and bring
them back so they can eat again," said Tom Lauletta, the former manager of
the Southwest plant.
The trick of the science is to judge the proper amount of sludge to
send back for a second meal. Sewage treatment plant operators often
characterize bacteria by their behavior. Bugs can be lazy, aggressive,
old, young, hungry or fat. Adolescent, virile bugs get sent back to eat
again. Old, indolent bugs get wasted.
"We're operating with a young sludge," Nicolo said. "We determine the
age by a mean cell-retention time before we waste it. We waste 300,000
gallons each day from the two tanks. We like to keep our sludge at about 3
1/2 days old."
Nicolo walked along the tanks, passing a trough that contained mixed
liquor. It looked like a bartender's practical joke. "Mixed liquor should
be a golden brown and not have too much odor," he said. "The tests to
measure the oxygen demand of sewage take five days to complete. By then
the sewage is long gone. So you operate the plant through your five
senses. This mixed liquor looks and smells just about right."
Often, a single source of sewage can make a great difference in the
character of the waste water entering a plant. "This is not the normal
color of our sewage," Nicolo said as he returned to the headworks. "This
is funny. It's usually more gray, and not this brown." The department's
investigators later determined that a building contractor had flushed a
large amount of dirt down the sewers.
Philadelphia's sewage today largely reflects the city's decline as a
manufacturing center. Industrial users accounted for 25 percent of the
sewer system's flow three decades ago, but now contribute only 7 percent
of the output. Today's sewage is more dilute. Not that the city misses the
industrial sewage; it contained toxic metals or chemicals that strained
the abilities of the treatment process.
The loss of other industries, however, was deeply lamented at the
Southeast plant. The sewage from Schmidt's Brewery, the Domino Sugar
refinery and Publicker's Distillery ended up at Southeast before they
closed. "Those places had great waste - all sugars and carbohydrates,"
said Thomas Healey, the head of the industrial waste unit. "It was good
food for the bugs."
UNTIL 1980, THE SLUDGE from
Southeast was loaded on a barge and dumped in the Atlantic Ocean. Nine
years ago, under pressure from the EPA, the city agreed to halt ocean
dumping and turned to composting. Nowadays, the sludge that the Southeast
plant wastes is pumped about five miles under the Schuylkill to the
Southwest plant. After it is condensed, it goes to the city's giant Sludge
Processing and Distribution Center, next to the Southwest plant.
Philadelphia's three plants produce about 175 dry tons of sludge a day,
and all of it is composted at the sludge processing facility. Dry ton,
however, is a misleading term; it refers to the weight of solids suspended
in a liquid. Sludge is anything but dry. Straight from the settlement
tanks, it is about 3 percent solid - very pourable. It solidifies somewhat
while it spends a month in closed tanks, when the microbes continue to
digest the waste. Afterward, it is wrung out in centrifuges and presses
and becomes known as "dewatered sludge cake," which is about 20 percent
solid. It has the consistency and the appearance of a fresh cow patty. A
dry ton of sludge cake, including the water, actually weighs about five
Sludge is William Toffey's business.
Two years ago, Toffey worked in the city planning office before taking
on the monumental job as the Water Department's sludge utilization
manager. When introduced to strangers, he does not hide the nature of his
work. "I tell them I sell sludge," he said. "It generates all sorts of
Selling sludge is nothing like selling encyclopedias. Toffey, 38, is
equipped with an Ivy League education and bearing. He has a bachelor's
degree in agronomy from Cornell University and a master's in environmental
planning from the University of Pennsylvania. Slender and high-strung, he
wears English-cut suits and wire-rim glasses. He uses such terms as
"marketing utilization decisions." At other times, he uses plain English:
"In order to maintain a consistent product, we screen out the solids that
can't be squished or mished or pulled out."
With loping strides, Toffey marched around the 42-acre
sludge-composting facility, the largest such operation in the United
States. All around him were mounds of sludge cake and wood chips,
smoldering from the 140-degree heat the compost generates. The heat kills
most of the disease-causing bacteria and after seven weeks leaves the
sludge looking at least something like earth.
Philadelphia produces several different sludge products, which it
markets under the trade names of Mine Mix, Philly Mulch and Earthlife. The
blends represent various mixtures of sludge and wood chips. "We didn't
want to put all our sludge eggs in one basket," said Toffey. A plane
approaching Philadelphia International Airport screamed overhead.
The original product - 15-year-old sludge that had been dredged from
lagoons at the Southwest plant - was called Philorganic. The department
gave it away in the late '70s. But as the department diversified its line,
Philorganic was also used to refer to sludge composted with wood chips and
then screened to achieve a fine loam. Confusion arose about Philorganic's
true identity, so that name was discarded and the screened material was
renamed Earthlife. "It is the finest, most value-added product we have to
offer," said Toffey. Earthlife sells for about $12 a ton, if it's bought
by the tractor-trailer load. Toffey said it is price-competitive with
other soil conditioners.
About 25 percent of the city's sludge cake is applied straight to strip
mines or farmland, just like manure. The rest is composted. A distributor
sells the compost to landscapers and garden centers, through which it most
often ends up beneath lawns or athletic fields. Despite assurances that
little of the metallic content is transmitted to plants, the city
maintains a conservative stand and recommends that the sludge not be
applied to land where crops are grown for human consumption. The warning,
Toffey acknowledged, is not a good marketing tool.
Sludge also has a short-lived odor when it is applied to the ground, an
aroma that farmers regard as earthy. Suburbanites say it stinks. "It's not
a popular program, especially when you get closer to suburban areas," said
Toffey. "It's been very disappointing."
The city first started using the sludge mixtures to reclaim abandoned
strip mines in Western Pennsylvania. Residents near the mines complained
loudly about having to live with Philadelphia's waste. Because of the
protests, fewer mines are being reclaimed today, even though studies of
the sites showed no contamination, and plant life thrived on the
Because of the fear of sludge products, the city's program is
struggling. As of January, the department had a four-month backlog of
sludge products - about 120,000 wet tons of sludge cake and Mine Mix -
stored at the processing facility.
Toffey views the sludge crisis as an irony of modern environmentalism:
"As a nation, we've raised the fears in order to raise the environmental
consciousness. But that fear has come around and bogged us down."
With New York and northern New Jersey cities on their way out of the
ocean - Congress has banned sludge dumping starting in 1991 - there will
be millions of tons of new sludge to deal with in the coming years. The
disposal options are limited. Sludge can be incinerated or sent to a
landfill, at considerable cost. The city once attempted to fuse sludge and
incinerator ash into a vitreous roadbed material it called Ecorock, but
the process was too expensive. Other processes to turn sludge into fuel
pellets are considered experimental. And so the most environmentally
conscientious - and cost effective - method remains composting.
Hence the city's focus on sludge. "If we can have a major success
here," said Toffey, "I think it will have a lot of effect swaying people
over to land application of sludge products." When the sludge-handling
improvements are finished this year, people driving by on I-95 can gaze
out on acre upon acre of composting sludge and feel proud for their small
contribution to that great mound.
More likely, however, is that they'll see acres of concrete tanks
filled with decomposing sewage. And, in the center of it all - hiding a
complex of digesters, aerators, sludge thickeners and enough plumbing to
reroute the Nile - rows of identical brick buildings. If you squint, they
look like classrooms.
"We actually got some complaints," Marrazzo said, "from people who
wondered how we allowed a junior college to get built in the middle of a
sewage treatment plant."
Sewage treatment cannot escape notice.
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