When it rains in our metropolis everything goes down the drain. Literally. Miles upon miles of paved, or impervious, surfaces channel rainwater into street drains where the liquid is mixed with everything that goes down our sinks, toilets and bathtubs. Under normal conditions, this mix of fluids and solids flows towards our wastewater treatment plants which clean the water and return it to our local waterways. However, when it rains the system is overwhelmed and the materials are released, untreated, into our waterways creating dangerous environmental conditions. In the first stage of wastewater treatment waters are "screened" for solids and other materials such as plastic bottles and (sometimes) live animals writes the NY Times in the article below. JB
By Corey Kilgannon
The best places to see the celebrated products of New York - its Broadway talent, its skyscraper architecture - are well known.
But the best place to see Manhattan's byproducts - what is stuffed down its sinks, flushed down its toilets and washed from its gutters - cannot be found in tour guides. There is perhaps no better vantage point than the Manhattan Grit Chamber, which strains solids from much of the borough's sewage as it flows underground to the Wards Island Wastewater Treatment Plant.
"This is where it all winds up," said John Ahern, who oversees the chamber, a large building at the eastern end of 110th Street in Manhattan, next to Franklin D. Roosevelt Drive.
The Manhattan chamber handles sewage from much of the Upper East Side and Upper Manhattan, which makes up about a third of the city's total. From the baby's bathwater to the dead rat washed down a curbside storm drain, from a slop sink at Gracie Mansion to a Washington Heights bodega bathroom, it all goes into the street sewers, which, in their intricate latticework, are laid out so that the sewage flows by gravity to one large main bound for a tunnel running under the East River to the plant on Wards Island, surrounded by Manhattan, Queens and the Bronx. There it is cleaned of toxins and released as purified water into the river.
To keep the tunnel clear, grit and other solid materials must be strained before the sewage enters. That's where the chamber comes in. It was opened in 1937 along with the Wards Island plant and the city's other grit chamber in the Bronx and strains sewage from the west Bronx. It also feeds the Wards Island plant.
At the Manhattan chamber, sewage enters through a 12-foot-wide main and flows into a basement room, where it is split into four canals, slowing its flow so that solids settle to the bottom. The sediment is collected by an arm that sweeps the bottom of the canal and empties into buckets that automatically rinse the grit and lift it up to the ground floor, where it is deposited in metal bins.
The detritus floating in the channels - yesterday, this included cigarette butts, bottle caps, plastic bottles, candy wrappers and plastic spoons - is skimmed out by a rake and pulled up an incline called a screen climber, which resembles an escalator, and is also deposited into bins.
They sit at the foot of the elegant columns gracing the building's Art Deco lobby, one of the aging Art Deco features in the building that are being restored. The refined architecture is at odds with the omnipresent stench.
The strained waste water proceeds along the canals and through sluice gates, then drops several hundred feet down a shaft into a nine-foot-wide tunnel running as much as 500 feet below the East River to the plant.
The bins of accumulated solids, called "screenings," are frequently dumped by forklift into larger ones for transport to Wards Island and are held there until they are shipped to landfills out of state. The whole process is costly, and might be less so if people paid more attention to what they flush down the drain, city officials say.