Transcript Wastewater Treatment System of New York City

Wastewater Treatment System
of New York City
December 17, 2008
Lindsey Walaski
Wastewater Treatment
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Basic Facts
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1.3 billion gallons of water is
delivered to 8 million City
inhabitants as well as 1 million
consumers living north of the
city.
The water network consisting
of 19 reservoirs and three
controlled lakes in a 1972
square mile watershed
extending 125 miles north and
west of New York City.
14 plants are located
throughout the five boroughs.
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Basic Facts
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The entire system consists of 14
wastewater plants; 6,000 miles of
sewer pipes; 135,000 sewer catch
basins; 494 permitted outfalls for the
discharge of combined sewer and
stormwater overflows.
Wastewater plants are managed by
the Department of Environmental
Protection Agency (DEP).
Bureau of Wastewater Treatment
(BWT) operates and maintains
sewage treatment.
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History
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The first reservoir system was created in 1842 after human and animal waste
polluted the water supply and distributed epidemics.
The first wastewater treatment plants were built in the late 1890s and 1900s in
Brooklyn and Queens.
Chemical coagulation was done for settling and chlorine was used seasonally
for disinfection.
In 1904, the Metropolitan Sewage commission was developed to survey and
analyze water quality after the connection between waterborne bacteria and
human diseases was made. The commission created construction for treatment
plants with good locations.
Between 1935 and 1945, three new plants were built, including the Wards Island
plant that serviced the east side of Manhattan and the Bronx. This plant began
using sludge processing to treat sewage.
A sixth plant was built, increasing the capacity to 497 million gallons per day
(mgd).
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History
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Five new plants were built between 1945 and 1965 to provide water for the
population of eight million people, increasing the capacity for sewage treatment
from 497 mgd to 1,037 mgd.
Several of the plants underwent upgrades, including the step aeration process.
The Newtown Creek wastewater plant was built and designed to treat 310 mgd.
The plant conserved space and minimized pumping requirements by not using
intermediate channels.
By 1968, there were 12 operating plants treating one billion gallons of water a
day and removing 65% of pollutants.
The Clean Water Act was passed in 1972, requiring plants to be upgraded to
secondary treatment and removing 85% of pollutants.
Today there are 14 working plants with a total capacity of 1,805.
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New York City Water Pollution Control Plant
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Wastewater Treatment Process
The purpose of wastewater treatment
plants is to remove pollutants from the
wastewater and release clean water.
Preliminary Treatment
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Incoming wastewater, called
influent, flows through screens to
remove large objects.
Primary Treatment
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The water enters a primary settling
tank for one to two hours, letting the
heavier particles to settle at the
bottom of the tank and the lighter
particles to float.
The floating particles are skimmed
from the top of the water.
The solid settling at the bottom at
the tank, primary sludge, are
pumped using cyclone degritters to
the sludge handling facility for
further processing.
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Wastewater Treatment Process
Secondary Treatment
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Air and seed sludge are combined with the wastewater to break down
further.
Microorganisms are released that consume remaining organic pollutants.
Process takes three to six hours.
Aerated wastewater flows into the final settling tanks.
Remaining secondary sludge is sent back into the settling tanks.
The wastewater flows through settling tank for two to three hours and
then passes through the disinfection tank.
Disinfection
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The water becomes purified by mixing with chlorine for a minimum of 1520 minutes.
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Sludge Treatment
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Thickening
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Water is separated from the sludge and is sent to the aeration tanks for
additional treatment.
Digestion
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Sludge is placed in digesters, oxygen free tanks, for 15 to 20 days.
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Anaerobic bacteria are produced to consume organic material.
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Sludge is converted to methane, carbon dioxide and water.
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Methane is used as an energy source.
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Digester sludge left in the tank is sent to a dewater facility.
Sludge Dewatering
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Large centrifuges separate the water from the solids in the sludge.
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Water is returned to the plant for processing.
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Biosolids are created in this step.
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Organic polymers are added to make the biosolids firmer.
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Biosolids
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Biosolids are used for fertilizers,
soil conditioners or to cover
inactive landfills.
Beneficial because of the
presence of nutrients and organic
contents.
Utilization of biosolids destroy
dangerous organisms and reduce
moisture content.
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Utilization of Biosolids
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Land Application
 Spread on land to deliver nutrients to soil.
Composting
 Mixed with bulking agent to decompose.
 Used as mulch or soil conditioner.
Alkaline Treatment
 Mixed with highly alkaline material to create a “soil-like” product.
 The product can be used in farming.
Heat Drying
 Heated to destroy pathogens and get rid of moisture.
 Remnants are fertilizer pellets.
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Environmental Concerns
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Toxic Substances
Dry Weather Discharge
Grease
Combined Sewer Overflows (CSO)
Floating Debris
Nutrients
Water Waste
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Industrial Pretreatment Program (IPP)
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A program federally authorized that initiates pretreatment regulations and forces
industries to remove certain pollutants from their wastewater before releasing it
into the sewer system.
The program also institutes pollutant limitations, wastewater sampling, reporting
requirements and facility inspections regularly.
Persistent Pollutant Track-Down Program:
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The DEP and Department of Environmental Conservation (DEC) collaborate
to determine the sources of toxins such as polychlorinated biphenols (PCBs),
poly-aromatic hydrocarbon (PAHs), and mercury. Procedures for
pretreatment will be implemented once sources are discovered.
PERC Reduction Program:
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Perchloroethylene (PERC) is a solvent used in dry cleaners that is released into the
sewer system. IPP implemented safe discharge amounts that dry cleaners must
adhere to.
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Water Quality Monitoring
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37 sampling stations are located
throughout the New York Harbor to
analyze water samples annually.
Process began in 1970.
The increase in dissolved oxygen
and decrease in fecal coliform
demonstrate an improvement in the
quality of water.
“Fish survival only” was an indicator
of the quality until 1988.
In 2001, many areas because
suitable for bathing.
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Keeping the Water Clean
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Water Conservation
Don’t release hazardous material into the sewer
system
Use Public Transportation
Don’t Litter
Dispose Grease Properly
Cooperate with Shoreline Cleanup and Surveys
Report Dry Weather
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Sources
"New York City." Information Center for the Environment.
<http://http://ice.ucdavis.edu/node/133>.
"New York City's Wastewater Treatment System." Department of Environmental
Protection. <http://http://www.nyc.gov/html/dep/pdf/wwsystem.pdf>.
Thank you for your attention!
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