Environmental Engineering Reference
In-Depth Information
About 170 million people rely on sewer systems that use separate
pipelines for rainwater and sanitary-sewer waste. An additional 40
million people in hundreds of cities depend on older, combined sewer
systems, which commingle storm water and sewage into one pipe during
rainstorms.
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During heavy storms, these combined pipes are often over-
loaded with harmful, and sometimes smelly, results. The EPA estimates
that these combined systems discharge 850 billion gallons of sewage and
storm water a year, enough to keep Niagara Falls roaring for eighteen
days.
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The combined systems have not been built since the 1950s and
are being replaced, but they still exist underground in many areas.
The danger these combined systems cause was well illustrated in late
October 2009 at the Owls Head Water Pollution Control Plant in Brook-
lyn, New York.
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Rain began falling, and by 1:00 A.M., a swimming
pool's worth of sewage and wastewater was rushing into the plant every
second. Owls Head quickly reached its capacity, and workers had to
shut the intake gates. That caused a rising tide throughout Brooklyn's
sewers, and untreated feces and industrial waste started spilling from
emergency release valves into Upper New York Bay and Gowanus Canal.
According to one of the plant's engineers, “It happens anytime you get
a hard rainfall. Sometimes all it takes is 20 minutes of rain, and you've
got overfl ows across Brooklyn.”
Between 2007 and 2009, more than 9,400 of the nation's 25,000
sewage systems (38 percent) reported violating the law by dumping
untreated or partly treated human waste, chemicals, and other hazardous
materials into rivers and lakes and elsewhere, according to data from
state environmental agencies and the EPA. Around New York City,
samples collected at dozens of beaches or piers have detected the types
of bacteria and other pollutants tied to sewage overfl ows from the city's
7,400 miles of sewer pipes.
In 2001, a report from Johns Hopkins researchers linked sewer over-
fl ows with diseases such as giardiasis, hepatitis A, and cryptosporidiosis.
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The study found that 68 percent of waterborne disease outbreaks over a
forty-seven-year period were preceded by high precipitation events, which
are increasing in frequency because of global warming (chapter 9).
New York is not alone with this problem. Researchers estimate that
as many as 4 million people become sick annually in California alone
from swimming in waters containing pollution from untreated sewage.
Today sewage systems are the nation's most frequent violators of the
Clean Water Act. Among the guilty since 2006 are San Diego, Houston,
Phoenix, San Antonio, Philadelphia, San Jose, and San Francisco.
