Platinum Award for Cedar Creek WPCP Thickeners Upgrade

The client required replacement of the original, 35-year-old sludge thickening system at the Cedar Creek WPCP. Hazen and Sawyer conducted an in-depth study and determined that in-kind replacement of the existing dissolved air flotation (DAF) system would not be the most efficient or effective.

Hazen and Sawyer determined gravity belt thickeners (GBTs) to be the better alternative. The new system occupies only half the space of the old one. The existing DAF tanks were repurposed to house piping and controls for the GBTs, which were installed on a concrete floor slab over the old DAF tanks.

The new GBTs generate 50% thicker sludge, which means greater efficiency further down the sludge treatment line. Due to reduced sludge volume leaving the thickening facility, one of the sludge digesters has been taken off line, saving energy. The new system also saves the client $1.2 million in annual operational costs over a DAF system, and the carbon footprint is now 30% lower than it would have been with in-kind replacement of the old system.

Because the sludge thickening process is now more efficient, an average of 50 fewer sludge-hauling trucks will enter and exit the plant every month, a 38% reduction.

Users of the adjacent Cedar Creek Park benefit from a cleaner park environment; besides fewer trucks through the park (the only means of access to the plant), the new system also provides better odor control.

(NEW YORK, NY – April 15, 2011) – The American Council of Engineering Companies – New York has bestowed the 2011 Platinum Award on the upgrade of gravity belt thickeners at the 76-mgd Cedar Creek Water Pollution Control Plant, located in Wantagh (NY) and operated by the Nassau County Department of Public Works.

This project required replacement of the original, aging sludge thickening system and outdated equipment to optimize efficiency. Sludge thickening is a critical step in the treatment process, allowing solids to be effectively removed from the influent wastewater. In its original configuration, the Cedar Creek sludge thickening system utilized a dissolved air flotation (DAF) process, in which tiny air bubbles were used to float solids to the top of eight DAF tanks within a dedicated sludge thickening building.

Using in-depth analysis of cost, performance, and overall impact on the treatment plant’s performance, Hazen and Sawyer determined that another technology, gravity belt thickeners (GBTs), would be more effective and efficient than in-kind replacement of the DAF system. GBTs utilize motor-driven belts to drain water from and thicken sludge.

Benefits for both the client and the public include:

  • Maximized use of existing space. The space-saving design utilizes only half of the existing space, repurposing four of the eight DAF tanks and leaving the client with additional space for storage or other future needs in the area currently occupied by the remaining four decommissioned DAF tanks.
  • Reduced energy consumption and greater performance efficiency. A 50% thicker sludge means greater efficiency in the solids treatment train, with reduced sludge volume leaving the thickening facility and the site. This results in reduced sludge heating requirements, increased digester and dewatering capacity, increased storage capacity, and reduced odor control chemical costs.
  • Decreased plant carbon footprint by 30%.
  • Cleaner air for users of adjacent Cedar Creek Park. Due to a more efficient thickening process, fewer sludge-hauling trucks enter and exit the plant, which is accessible only through the park.
  • Significantly lower annual operational costs for solids treatment, by about $1.2 million.

The new GBT system cleverly reuses a portion of the existing space that had previously housed the DAF system. The GBTs (along with chemical storage and new access walkways) were installed atop concrete slab over the decommissioned DAF tanks. The interiors of four of the old tanks were gutted and repurposed to house all necessary piping for the new system. Stairs lead from the operating level down to the gallery within the tanks for ease of operator access.

Since our founding in 1951, Hazen and Sawyer has focused on two things: providing safe drinking water and controlling water pollution. Our range of services encompasses the planning, design, and construction management of water and wastewater-related projects – from clean water treatment, storage, and distribution to wastewater and stormwater collection, treatment, and reuse.

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