Insights

WWTF Achieves Stringent Phosphorus and Zinc Goals

WWTF Achieves Stringent Phosphorus and Zinc Goals

First Ballasted Flocculation Facility of Its Kind in Rhode Island

The Town of Smithfield Wastewater Treatment Facility discharges treated effluent into the environmentally sensitive Woonasquatucket River. The Rhode Island Department of Environmental Management (RIDEM) issued a discharge permit with more stringent discharge requirements for a year-round total zinc concentration of 50.1 µg/L (daily maximum and monthly average), and a seasonal effluent total phosphorus concentration of 0.2 mg/L between April and October.

The Smithfield Sewer Authority (SSA) implemented a $7 million tertiary treatment upgrade program to meet the more stringent discharge requirements. Wright-Pierce based its tertiary treatment technology evaluation not only on the ability to reliably satisfy the more stringent discharge requirements, but also considered construction cost, O&M costs, operational flexibility, the technology’s proven track-record, and a 30-year life-cycle cost analysis.

Ballasted flocculation was ultimately selected for the tertiary upgrade because pilot testing confirmed it would meet the revised permit limits at the lowest lifecycle cost. Kruger’s new Actiflo® Turbo system was the selected ballasted flocculation system due to the tight space constraints and the smaller footprint of the system.

The Actiflo Turbo system consumes significantly less energy than the classic ballasted flocculation system. As a result the Rhode Island Clean Water Finance Agency considered the project qualified for Green Project Reserve (GPR) status, and granted the Town principal forgiveness for approximately $1.4 million. The upgraded facility has been operational since the summer of 2014 and is achieving regulatory standards. This was the first ballasted flocculation facility of its kind in Rhode Island.