Jan 29, 2019

New York City’s Aging Sewer System

New York City's sewer system is aging, releasing untreated water sewage and stormwater runoff every year into its waterways.

 New York City releases untreated water sewage and stormwater runoff every year into its waterways
New York City releases untreated water sewage and stormwater runoff every year into its waterways.

Every year, New York City release 100 billion liters of untreated water sewage and stormwater runoff into its waterways. According to City Limits, when it rains heavily, stormwater forces the sewer to hit maximum capacity, causing wastewater to flow from the aging system into nearby rivers.

The city is currently working on different ways to improve the water quality. However, the efforts might not be enough. According to City Limits, researches at Queen College found that pollution from the overflow may be contributing to greenhouse gases in nearby marshes.

“The take home message [was] carbon additions increased both carbon dioxide and methane production in wetland soils,” said Dr. Brian Brigham, lead study author, to City Limits.

The wetlands typically serves as carbon sinks. Carbon sinks are areas that can absorb carbon dioxide form the atmosphere. The carbon is trapped and stored through a process called biological carbon sequestration. According to City Limits, wetland vegetation and soil accumulate organic matter. This is anything that includes carbon, before decomposing and emitting it through natural respiration. It is estimated that wetlands store about 35% of all land-based carbon, according to City Limits.

The U.S. has lost more than half of its original wetland areas because of agricultural and urban developments, according to City Limits. When it rains a lot, and human pollutants are carried by the excess stormwater into surround waterways, wetlands lose their ability to contain the carbon allowing more greenhouse gases to enter the atmosphere.

Brigham and his team added certain types of carbon and nitrogen commonly found in sewage-polluted environments to three different marshes along the Hudson River to show this. In each sample, they took mud, soil and microbes and simulated in the lab what would happen if sewage had been added. According to City Limits, they found that the added carbon increased carbon dioxide production rates 1.4 to 2 times more in the treated soils than in the controls.

According to City Limits, salty environments inhibit methane production. The less salinity a marsh has, the more methane is produced. Extra carbon caused greater methane production in Piermont and Iona Island compared to the saltier waters of Staten Island’s Saw Mill Creek Marsh, according to City Limits. Every influx of stormwater carrying human pollutants from the sewers brings along excess carbon, which fuels microbial respiration, producing more methane.