The Port Washington Water Pollution Control District owns and operates a wastewater treatment plant originally constructed in 1951 with a design flow of 4 MGD. Treated effluent is discharged into Manhasset Bay. The plant was upgraded in 1987-1989 to achieve secondary treatment levels and then again in 2010 to implement a full scale biological nutrient removal (BNR)/Nitrogen removal system. This 2010 project was implemented as a result of the Long Island Sound Study (LISS) findings.
The LISS was initiated in 1985 by a partnership between the federal government and the states of Connecticut and New York. This study identified nitrogen discharges from various sources to be the major culprit of low dissolved oxygen levels in the Sound – stress and death of aquatic organisms. It recommended that to improve the conditions in the Sound, the total nitrogen loading contributed by Publicly Owned Wastewater Treatment Plants (POTW’s) on the North Shore of Long Island and the Upper East River NYC plants, be reduced to 65% below a 1990 baseline discharge level by 2014.
In response, the District launched a successful Biological Nutrient Removal (BNR) demonstration project in 2001 to reduce nitrogen discharges, the first such pilot program on the North Shore. This project successfully gained operating experience, developed design criteria for the permanent BNR system and assisted in determining operating and maintenance costs required to meet the 2014 limit. This demonstration project was so successful that it was kept in operation to achieve the interim nitrogen removal limits until the full-scale project was completed in 2010.
As a result, the District has exceeded expectations and met the total nitrogen NYSDEC limits ahead of the permit required dates.
The District has had no exceedances with the Total Nitrogen Limit. On average, the District reduces Total Nitrogen loading to the Sound by 83% and at times over a 90% reduction is achieved, well above the 1990 65% reduction goal.
