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Wastewater Treatment System of New York City

December 17, 2008

Lindsey Walaski

Wastewater Treatment

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Basic Facts

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

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

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

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.

1. Preliminary Treatment• Incoming wastewater, called

influent, flows through screens to remove large objects.

2. Primary Treatment• 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 Process3. Secondary Treatment

• 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.

4. Disinfection• The water becomes purified by mixing with chlorine for a minimum of 15-

20 minutes.

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Sludge Treatment

Thickening Water is separated from the sludge and is sent to the aeration tanks for

additional treatment. Digestion

Sludge is placed in digesters, oxygen free tanks, for 15 to 20 days. Anaerobic bacteria are produced to consume organic material. Sludge is converted to methane, carbon dioxide and water. Methane is used as an energy source. Digester sludge left in the tank is sent to a dewater facility.

Sludge Dewatering Large centrifuges separate the water from the solids in the sludge. Water is returned to the plant for processing. Biosolids are created in this step. Organic polymers are added to make the biosolids firmer.

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Biosolids

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

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

Toxic Substances Dry Weather Discharge Grease Combined Sewer Overflows (CSO) Floating Debris Nutrients Water Waste

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Industrial Pretreatment Program (IPP) 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: 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: 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

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

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!