Nitrogen Removal

Narragansett Bay Commission has significant initiatives related to nitrogen removal at both the Field's Point and Bucklin Point treatment facilities. These projects are required as part of Consent Agreements with the Rhode Island Department of Environmental Management (RIDEM).

Field's Point

The planned Biological Nutrient Reduction (BNR) facilities at Field's Point include the replacement of the scum concentrator, grit washers and the drive mechanisms for the primary and final clarifiers and the gravity thickeners which are near the end of their useful life. It has also been determined that a new operations building is required for all of the new computer control systems for BNR, the Tunnel Pump Station, the Ernest Street Pumping Station and wastewater operations. In addition, as part of this project, chemical storage tanks will be constructed for sodium hydroxide and methanol, the chemicals used in the nitrification / denitrification process. Furthermore, upgrades will be made to the current electrical service to provide additional power, and new energy efficient blowers will be added for the additional required process air.

At Field’s Point, upgrades will be made within the ten existing aeration tanks in order to attain the nitrification / denitrification needed to meet the limits. Each aeration basin will be subdivided into a series of aerated and anoxic reactors with suspended plastic media in the aerated portion of each tank, otherwise known as the Integrated Fixed Film Activated Sludge (IFAS). These engineered plastic media or biocarriers allow a biofilm to grow protected within their interior structure. The biofilm break down and remove wastewater pollutants, by using them as a supply of food. The result is a reduced level of nitrogen in the discharged effluent. NBC will incorporate the free-floating K3 media from the contracted IFAS vendor. The existing screw lift pumps to the aeration tanks will also have to be replaced in order to get gravity flow through the modified aeration tanks.

Bucklin Point

Prior to entering into the Consent Agreement with RIDEM for BNR at Bucklin Point, NBC designed and constructed new nitrogen removal facilities at Bucklin Point that were designed to achieve a total nitrogen limit of 8mg/l. NBC has worked diligently to maximize nitrogen removal at Bucklin Point and has achieved significant reductions in nitrogen loading. However, NBC has determined that additional modifications are required to achieve compliance with the nitrogen limit of 5 mg/l as set forth in the Consent Agreement.