Combined Sewer Overflows (CSOs) Impact on Water Quality and Environmental Ecosystem in the Harlem River

Abstract

The Harlem River, a 9.3-mile channel that flows from the Hudson River to the East River, has experienced decades of industrial abuse and remains gritty and industrial. During heavy rains, the pipes discharge raw sewage into the river through combined sewer overflows (CSOs) that can contain bacteria and cause illness. Water samples were collected from CSO discharge point and several adjacent sites along the river in the Bronx side close to River Park Towers at Richman Plaza and Manhattan side at Wards Island. Nutrients, bacteria, polychlorinated biphenyls (PCBs), and fish consumption safety have been analyzed. Results showed that phosphorus, ammonia concentration as well as fecal coliform, E.Coli, enterococcus levels increased significantly during heavy rainstorms. Ammonia concentration was up to 2.725 mg/L during tropical storm Arthur on July 2, 2014 and rainstorm in May 2013, and soluble reactive phosphorus (SRP) or orthophosphate was up to 0.197 mg/L during heavy thunderstorm in April 2011; both nutrients were exceeded EPA regulation for ammonia (0.23 mg/L) and phosphate (0.033 mg/L) for New York City (NYC) waters. The colonies of fecal coliform were more than 5 million MPN/100ml (most probable number per 100 ml) during tropical storm Arthur in July 2014 and heavy rainstorm in April 2014, and fecal coliform was more than 10,000 MPN/100ml during storm in July and November 2013; E.Coli reached more than 5000 MPN/100ml during tropical storm Arthur and storm in May 2013; enterococcus reached more than 10,000 MPN/100ml during tropical storm Arthur and heavy rainstorm in April 2014. These bacteria (pathogen) levels in the Harlem River were significantly higher than EPA standards (fecal coliform: 200 MPN/100ml, E.Coli: 126 MPN/100ml, enterococcus: 104 MPN/100ml), especially during rainstorm/tropical storm. Of particular significance, nutrients and bacteria were analyzed before and after Hurricane Sandy devastated NYC in late October 2012; results determined that bacteria and ammonia concentrations increased after this monumental storm, elucidating the environmental impact of large storm events. PCB 11 (3,3’-dichlorobiphenyl, C 12 H 8 C l2 ), the high molecular weight (MW), an indicator of raw sewer and storm water runoff in the NYC harbor waters, is the major polychlorinated biphenyls (PCBs) in the Harlem River. PCBs are carcinogenic, which could bioaccumulate via food chain from fish and seafood, endangering public health. Oyster farming has been used to purify water and improve water quality in the river. CSOs and storm water runoff have degraded water quality and been threatening environmental ecosystem and public health. This research will help local communities understand CSO impact on nutrients, bacteria, PCBs contamination and fish consumption safety, and make contributions on CSOs reduction as well as improve water quality and environmental ecosystem in the Harlem River.